CN111100862A

CN111100862A - A method for detecting bacterial serotypes

Info

Publication number: CN111100862A
Application number: CN201811257716.4A
Authority: CN
Inventors: 廖逸群; 李庆阁; 杜琛; 许晔
Original assignee: Xiamen University
Current assignee: Xiamen University
Priority date: 2018-10-26
Filing date: 2018-10-26
Publication date: 2020-05-05
Anticipated expiration: 2038-10-26
Also published as: CN111100862B

Abstract

The present application provides a method for detecting bacterial serotypes, which can simultaneously detect multiple bacterial serotypes (eg Escherichia coli O serotype, Escherichia coli H serotype, Escherichia coli K serotype, Salmonella O serotype, Salmonella serotype H, Vibrio parahaemolyticus serotype O, Vibrio parahaemolyticus serotype K, Shigella serotype O, Vibrio cholerae serotype O, etc.) in the sample. In addition, the present application also provides a probe set and a kit comprising one or more of the probe sets, which can be used to implement the methods of the present invention. In addition, the present application also provides a kit capable of simultaneously detecting the presence or level of multiple bacterial serotypes in a sample in one round of reaction.

Description

Method for detecting bacterial serotype

Technical Field

The present application relates to multiplex detection of nucleic acid molecules. In particular, the present application provides a method of detecting bacterial serotypes, which method is capable of detecting the presence of bacteria of multiple (e.g., 2,5, 10, 15, 20, 25, 30 or more) serotypes simultaneously in a sample. In addition, provided herein are probe sets, and kits comprising one or more of the probe sets, which can be used to practice the methods of the invention. In addition, the present application provides a kit that is capable of simultaneously detecting the presence of multiple (e.g., 2,5, 10, 15, 20, 25, 30 or more) serotypes of bacteria in a sample in a single round of reaction.

Background

Serotype typing of bacteria refers to the further classification of bacteria of the same species based on differences in their antigenic determinants. The bacterial serotype typing is a universal bacterial identification and traceability technology at home and abroad, and the bacterial antigen types used for the bacterial serotype typing mainly comprise an O antigen, an H antigen and a K antigen. The current bacterial serotype typing test method is a traditional antibody seroagglutination test, i.e. the serotype of the bacteria is recognized by the specificity of antibody-antigen. Antibody seroagglutination assays require the preparation of large quantities of high purity antibody sera of different types and multiple agglutination assays to identify bacterial serotypes, and the phenomenon of serum self-agglutination often interferes with interpretation of results. Compared with antibody serum agglutination detection, the nucleic acid detection of the antigen encoding gene has the remarkable advantages of strong result repeatability, good specificity, simple and convenient operation, low cost and the like. Therefore, a large number of literatures and patents at home and abroad report that a nucleic acid detection method is adopted to detect the bacterial antigen coding gene and the corresponding serotype. On the basis, most nucleic acid detection methods adopt a multiplex PCR amplification technology to improve the efficiency and sensitivity of the detection method. Real-time PCR is a common method for detecting nucleic acid, and has simple operation and wide application. And, by using multiple real-time PCR, a plurality of target sequences can be simultaneously detected in a single reaction tube, which not only improves the detection efficiency, but also reduces the cost.

In real-time PCR methods, target sequences can be detected by using fluorescently labeled oligonucleotide probes. In general, a fluorescently labeled probe specifically binds to a target sequence between two primers used for PCR amplification to avoid interfering signals caused by non-specific amplification of primer dimers, improving the specificity of the detection result. For multiplex real-time PCR, when multiple oligonucleotide probes specific for a target sequence are used, each oligonucleotide probe can be labeled with a different fluorophore, whereby the target sequence specifically recognized by each probe can be detected by detecting the unique fluorescent signal carried by each probe. In the real-time PCR method, the target sequence can be detected by two modes, namely, a real-time detection mode and a post-amplification melting curve analysis (also referred to as post-PCR MCA mode). In the real-time detection mode, the detection of the target sequence and the PCR amplification are performed simultaneously, without performing additional steps. Therefore, the real-time detection mode is simple and direct. However, the maximum number of target sequences that can be detected in this mode in a single round of detection is limited by the number of fluorescent detection channels of the real-time PCR instrument, and generally does not exceed 6. In the MCA mode, an additional step after PCR amplification is required, namely analysis of the melting point of the duplex formed by the probe and the target sequence. The MCA pattern may identify or distinguish target sequences by fluorescence color and/or melting point. Thus, the MCA model, while relatively cumbersome (i.e., adds an additional step), increases the number of maximal target sequences that can be detected in a single round of detection.

However, multiplex real-time PCR based on fluorescent probe detection also presents some problems. First, the preparation of fluorescent probes involves complex chemical modification and purification processes, which are much more costly than non-labeled probes. Therefore, the use of a plurality of fluorescent probes leads to an increase in detection cost. Secondly, in the multiplex real-time PCR method, the coexistence of a plurality of fluorescent probes increases the background fluorescence of the reaction system, which in turn may cause a decrease in detection sensitivity. Therefore, there is a need for improvements in multiplex real-time PCR methods in order to detect as many target sequences as possible with as few fluorescent probes as possible.

Faltin et al (Clinical Chemistry 2012,58(11):1546-1556) describe a real-time PCR detection method based on "mediator probes". In the conventional real-time PCR detection method, a fluorescent probe specific to each target sequence is used. However, in the method reported by Faltin et al, two probes need to be used for each target sequence: one mediator probe specific for the target sequence that is not fluorescently labeled, and another fluorescently labeled probe (fluorescent probe) that does not bind to the target sequence; wherein, the vector probe consists of a target specificity sequence at the 3 '-end and a label sequence (vector) at the 5' -end; the fluorescent probe is composed of a 3 '-end single-chain sequence containing a mediator hybridization site and a 5' -end sequence which contains a quenching group and a fluorescent group and has a hairpin structure, wherein the quenching group and the fluorescent group are both positioned on the arms of the hairpin structure and are close to each other, so that fluorescence quenching occurs. In the PCR process, the mediator probe is combined with a target sequence through a target specific sequence, and a tag sequence (mediator) at the 5' -end of the mediator probe keeps a single-stranded free state; subsequently, the mediator probe is subjected to enzyme digestion under the action of DNA polymerase with 5 '-nuclease activity, and the mediator with 3' -OH is released. Subsequently, the released mediator binds to the mediator hybridization site in the fluorescent probe and is extended by polymerase, resulting in the cleavage or displacement of the sequence labeled with the quencher, thereby causing the separation of the fluorescent group from the quencher, resulting in an increase in fluorescence intensity.

The method described by Faltin et al is characterized in that the generation of the fluorescent signal is dependent on two probes: a mediator probe and a fluorescent probe; wherein the mediator probe is used as a hybridization probe and is not fluorescently labeled per se; the fluorescent probe is used to generate a fluorescent signal that specifically binds to the mediator, but not to the target sequence. In this method, a fluorescent probe can be used as a universal probe. For example, when multiple target sequences are detected using single real-time PCR, PCR reactions can be performed separately using multiple mediator probes, each carrying a unique target-specific sequence but containing the same mediator sequence, and one and the same fluorescent probe. In addition, for multiplex real-time PCR, multiple mediator sub-probes and one fluorescent probe with the same mediator sub-sequence can also be used to achieve screening of multiple target sequences when there is no need to identify or distinguish each target sequence. Compared with the conventional real-time PCR method, the method of Faltin et al can use a common fluorescent probe to detect a plurality of target sequences without synthesizing a unique fluorescent probe for each target sequence, which significantly reduces the detection cost.

However, the Faltin et al approach also suffers from significant drawbacks. In particular, when the method of Faltin et al is used to perform multiplex real-time PCR where each target sequence needs to be distinguished, it is necessary to design a mediator probe carrying a target-specific sequence and a corresponding fluorescent probe carrying a unique fluorescent signal for each target sequence. In this case, the Faltin et al method requires the use of double the number of probes, as compared to conventional multiplex real-time PCR using a single probe for each target sequence. Accordingly, the whole reaction system becomes more complicated and the detection cost becomes higher. For example, Faltin et al disclose a dual PCR method for simultaneously detecting HPV18 and the human ACTB gene, in which 2 mediator probes and 2 fluorescent probes are used; in contrast, the conventional dual real-time PCR method requires only 2 fluorescent probes. Similar examples are also found in Wadle S et al (Biotechniques 2016,61(3):123-8), which describes a quintuple PCR system using a total of 5 mediator probes and 5 fluorescent reporter probes. In contrast, the conventional quintuple real-time PCR method requires only 5 fluorescent probes. In this case, the Faltin et al method is more complicated and costly than the conventional multiplex real-time PCR.

US 2013/0109588 a1 discloses a real-time PCR assay useful for melting curve analysis, which, like the method of fantin et al, enables detection of a target sequence by means of two probes (a PTO probe, which corresponds to a mediator sub-probe, and a CTO probe, which corresponds to a fluorescent probe). Accordingly, the method of US 2013/0109588 a1 has similar advantages and disadvantages as the method of fantin et al. In particular, when the method described in this patent application is used to perform multiplex real-time PCR, which requires distinguishing each target sequence, it is necessary to design one PTO probe and one CTO probe for each target sequence, respectively; i.e., a double number of probes is used. For example, this patent application describes a dual real-time PCR for simultaneous detection of Neisseria gonorrhoeae and Staphylococcus aureus, using 2 PTO probes and 2 CTO probes. In this case, the method of US 2013/0109588 a1 is more complex and costly than conventional multiplex real-time PCR using a single probe for each target sequence.

US 2014/0057264 a1 discloses another real-time PCR method using two probes. In this method, the fluorescence signal is generated by cleavage of the labeled probe, and therefore, this method can be used only in the real-time detection mode, but not in the MCA mode. Furthermore, similar to the method of Faltin et al, when the method described in US 2014/0057264A 1 is used to perform multiplex real-time PCR requiring discrimination of each target sequence, two probes need to be designed separately for each target sequence, which results in a more complicated reaction system and is costly.

US 2015/0072887 a1 discloses a real-time PCR assay useful for melting curve analysis, which achieves detection of target sequences by 3 probes. However, when the method described in this patent application is used to perform multiplex real-time PCR requiring discrimination of each target sequence, 3 probes need to be designed for each target sequence separately, which results in a more complicated reaction system and high cost. Similar real-time PCR assays using 3 probes are also disclosed in US 2015/0167060 a1 and US 2016/0060690 a 1. However, these methods are similar to the methods disclosed in US 2015/0072887 a1, and are more complex and costly than conventional real-time PCR methods when used to perform multiplex real-time PCR that requires distinguishing between each target sequence.

In general, improved real-time PCR methods using two or three probes (e.g., fantin et al) have significant advantages over traditional real-time PCR methods when performing single real-time PCR or multiplex real-time PCR without the need to identify or distinguish between each target sequence: that is, multiple mediator probes carrying the same mediator sequence but different target-specific sequences and a common fluorescent probe can be used, thereby significantly reducing the detection cost. However, when performing multiplex real-time PCR, which requires the differentiation of each target sequence, these improved real-time PCR methods require the use of double or even triple probes, which are more complicated and costly than conventional real-time PCR methods.

In the present application, the inventors developed a novel real-time PCR assay method that can distinguish and identify each target sequence in a sample with a simpler reaction system and at a lower detection cost. On the basis, the inventor of the application develops a rapid, simple, sensitive, specific, stable and reliable high-throughput nucleic acid detection method and a kit, which can be used for detecting various bacterial serotypes (such as Escherichia coli O serotype, Escherichia coli H serotype, Escherichia coli K serotype, Salmonella O serotype, Salmonella H serotype, Vibrio parahaemolyticus O serotype, Vibrio parahaemolyticus K serotype, Shigella O serotype, Vibrio cholerae O serotype and the like).

Disclosure of Invention

Definition of terms

In the present invention, unless otherwise specified, scientific and technical terms used herein have the meanings that are commonly understood by those skilled in the art. Also, the nucleic acid chemistry laboratory procedures used herein are all conventional procedures widely used in the corresponding field. Meanwhile, in order to better understand the present invention, the definitions and explanations of related terms are provided below.

As used herein, the term "bacterial serotype" refers to a group of strains that share a unique surface structure (e.g., surface antigen). For example, a group identified by the outermost portion of lipopolysaccharide (O antigen) covering the surface of bacteria is called an O serotype, a group identified by the bacterial flagella (H antigen) is called an H serotype, and a group identified by the bacterial capsule (K antigen) is called a K serotype.

As used herein, the terms "target nucleic acid sequence", "target nucleic acid", and "target sequence" refer to the target nucleic acid sequence to be detected. In the present application, the terms "target nucleic acid sequence", "target nucleic acid" and "target sequence" have the same meaning and are used interchangeably.

As used herein, the term "mediator probe" refers to a single-stranded nucleic acid molecule containing a mediator sequence and a targeting sequence (i.e., target-specific sequences) in the 5 'to 3' direction. In the present application, the mediator sequence does not contain a sequence complementary to the target nucleic acid sequence, and the target-specific sequence contains a sequence complementary to the target nucleic acid sequence. Thus, under conditions that allow nucleic acid hybridization, annealing, or amplification, the mediator probe hybridizes or anneals to the target nucleic acid sequence through the target-specific sequence (i.e., forms a double-stranded structure), and the mediator sequence in the mediator probe does not hybridize to the target nucleic acid sequence but is in an episomal state (i.e., maintains a single-stranded structure).

As used herein, the terms "targeting sequence" and "target-specific sequence" refer to a sequence capable of selectively/specifically hybridizing or annealing to a target nucleic acid sequence under conditions that allow for hybridization, annealing, or amplification of the nucleic acid, which comprises a sequence complementary to the target nucleic acid sequence. In the present application, the terms "targeting sequence" and "target-specific sequence" have the same meaning and are used interchangeably. It is readily understood that the targeting or target-specific sequence is specific for the target nucleic acid sequence. In other words, under conditions that allow nucleic acid hybridization, annealing, or amplification, the targeting or target-specific sequence hybridizes or anneals only to a particular target nucleic acid sequence, and not to other nucleic acid sequences.

As used herein, the term "mediator sequence" refers to a stretch of oligonucleotide sequence in the mediator probe that is not complementary to the target nucleic acid sequence, which is located upstream (5' to) the target-specific sequence. In the present application, a unique mediator probe having a unique mediator subsequence (in other words, the mediator subsequences in all the mediator probes used are different from each other) is designed or provided for each target nucleic acid sequence; thus, each target nucleic acid sequence corresponds to a unique mediator probe (unique mediator sequence). Thus, by detecting the unique mediator sequence, the target nucleic acid sequence corresponding thereto can be detected.

As used herein, the term "upstream oligonucleotide sequence" refers to an oligonucleotide sequence comprising a sequence complementary to a target nucleic acid sequence that is capable of hybridizing (or annealing) to the target nucleic acid sequence under conditions that allow nucleic acid hybridization (or annealing) or amplification and, when hybridized to the target nucleic acid sequence, is upstream of a mediator probe.

The term "complementary" as used herein means that two nucleic acid sequences are capable of forming hydrogen bonds between each other according to the base pairing principle (Watton-Crick principle) and thereby forming a duplex. In the present application, the term "complementary" includes "substantially complementary" and "fully complementary". As used herein, the term "fully complementary" means that each base in one nucleic acid sequence is capable of pairing with a base in another nucleic acid strand without mismatches or gaps. As used herein, the term "substantially complementary" means that a majority of the bases in one nucleic acid sequence are capable of pairing with bases in another nucleic acid strand, which allows for the presence of mismatches or gaps (e.g., mismatches or gaps of one or several nucleotides). Typically, two nucleic acid sequences that are "complementary" (e.g., substantially complementary or fully complementary) will selectively/specifically hybridize or anneal and form a duplex under conditions that allow the nucleic acids to hybridize, anneal, or amplify. For example, in the present application, the target-specific sequences in the upstream oligonucleotide sequence and the mediator probe each comprise a sequence that is complementary (e.g., substantially complementary or fully complementary) to the target nucleic acid sequence. Thus, the target-specific sequences in the upstream oligonucleotide sequences and mediator probes will selectively/specifically hybridize or anneal to the target nucleic acid sequences under conditions that allow for nucleic acid hybridization, annealing, or amplification. Accordingly, the term "non-complementary" means that two nucleic acid sequences do not hybridize or anneal under conditions that allow for hybridization, annealing, or amplification of the nucleic acids, and do not form a duplex. For example, in the present application, the mediator sequence comprises a sequence that is not complementary to the target nucleic acid sequence. Thus, under conditions that allow nucleic acid hybridization, annealing, or amplification, the mediator sequence does not hybridize or anneal to the target nucleic acid sequence, cannot form a duplex, but is in a free state (i.e., remains a single-stranded structure).

As used herein, the terms "hybridization" and "annealing" refer to the process by which complementary single-stranded nucleic acid molecules form a double-stranded nucleic acid. In the present application, "hybridization" and "annealing" have the same meaning and are used interchangeably. In general, two nucleic acid sequences that are completely or substantially complementary can hybridize or anneal. The complementarity required for two nucleic acid sequences to hybridize or anneal depends on the hybridization conditions used, particularly the temperature.

As used herein, "conditions that allow nucleic acid hybridization" have the meaning commonly understood by those skilled in the art and can be determined by conventional methods. For example, two nucleic acid molecules having complementary sequences can hybridize under suitable hybridization conditions. Such hybridization conditions may involve the following factors: temperature, pH, composition, ionic strength of the hybridization buffer, etc., and can be determined based on the length and GC content of the two complementary nucleic acid molecules. For example, when the length of two complementary nucleic acid molecules is relatively short and/or the GC content is relatively low, low stringency hybridization conditions can be used. High stringency hybridization conditions can be used when the two nucleic acid molecules that are complementary are relatively long in length and/or relatively high in GC content. Such hybridization conditions are well known to those skilled in the art and can be found, for example, in Joseph Sambrook, et al, Molecular Cloning, Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. (2001); and m.l.m.anderson, Nucleic Acid Hybridization, Springer-Verlag New yorkinc.n.y. (1999). In the present application, "hybridization" and "annealing" have the same meaning and are used interchangeably. Accordingly, the expressions "conditions allowing hybridization of nucleic acids" and "conditions allowing annealing of nucleic acids" also have the same meaning and are used interchangeably.

As used herein, the expression "conditions that allow nucleic acid amplification" has the meaning generally understood by those skilled in the art, which refers to conditions that allow a nucleic acid polymerase (e.g., a DNA polymerase) to synthesize one nucleic acid strand using the other nucleic acid strand as a template and form a duplex. Such conditions are well known to those skilled in the art and may involve the following factors: temperature, pH, composition, concentration, ionic strength, etc. of the hybridization buffer. Suitable nucleic acid amplification conditions can be determined by conventional methods (see, e.g., Joseph Sambrook, et al., Molecular Cloning, A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. (2001)). In the method of the present invention, the "conditions which allow nucleic acid amplification" are preferably working conditions of a nucleic acid polymerase (e.g., a DNA polymerase).

As used herein, the expression "conditions that allow a nucleic acid polymerase to perform an extension reaction" has the meaning generally understood by those skilled in the art, which refers to conditions that allow a nucleic acid polymerase (e.g., a DNA polymerase) to extend one nucleic acid strand as a template for another nucleic acid strand (e.g., a primer or a probe), and form a duplex. Such conditions are well known to those skilled in the art and may involve the following factors: temperature, pH, composition, concentration, and ionic strength of the hybridization buffer, and the like. Suitable nucleic acid amplification conditions can be determined by conventional methods (see, e.g., Joseph Sambrook, et al., molecular cloning, A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. (2001)). In the method of the present invention, the "condition that allows the nucleic acid polymerase to perform the extension reaction" is preferably a working condition of the nucleic acid polymerase (e.g., DNA polymerase). In the present application, the expressions "conditions allowing a nucleic acid polymerase to perform an extension reaction" and "conditions allowing nucleic acid extension" have the same meaning and are used interchangeably.

As used herein, the expression "conditions which allow cleavage of the mediator probe" refers to conditions which allow an enzyme having 5' nuclease activity to cleave the mediator probe hybridized to the target nucleic acid sequence and release a nucleic acid fragment comprising the mediator sequence or a portion thereof. In the method of the invention, the conditions which allow cleavage of the mediator probe are preferably working conditions for an enzyme having 5' nuclease activity. For example, when the enzyme having 5 'nuclease activity used is a nucleic acid polymerase having 5' nuclease activity, the conditions that allow cleavage of the mediator probe may be the working conditions of the nucleic acid polymerase.

The working conditions for the various enzymes can be determined by the person skilled in the art by conventional methods and can generally involve the following factors: temperature, pH of the buffer, composition, concentration, ionic strength, etc. Alternatively, conditions recommended by the manufacturer of the enzyme may be used.

As used herein, the term "nucleic acid denaturation" has the meaning commonly understood by those skilled in the art, which refers to the process of dissociation of a double-stranded nucleic acid molecule into single strands. The expression "conditions which allow denaturation of nucleic acids" means conditions which allow dissociation of double-stranded nucleic acid molecules into single strands. Such conditions can be routinely determined by those skilled in the art (see, e.g., joseph sambrook, et al, Molecular Cloning, a Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, n.y. (2001)). For example, the nucleic acid can be denatured by conventional techniques such as heating, alkali treatment, urea treatment, enzymatic methods (e.g., methods using helicase), and the like. In the present application, preferably, the nucleic acid is denatured under heating. For example, nucleic acids can be denatured by heating to 80-105 ℃.

As used herein, the term "upstream" is used to describe the relative positional relationship of two nucleic acid sequences (or two nucleic acid molecules) and has the meaning commonly understood by those skilled in the art. For example, the expression "one nucleic acid sequence is located upstream of another nucleic acid sequence" means that, when arranged in the 5' to 3' direction, the former is located at a more advanced position (i.e., a position closer to the 5' end) than the latter. As used herein, the term "downstream" has the opposite meaning as "upstream".

As used herein, the term "fluorescent probe" refers to a piece of oligonucleotide that carries a fluorophore and is capable of generating a fluorescent signal. In the present application, a fluorescent probe is used as a detection probe.

As used herein, the term "melting curve analysis" has the meaning commonly understood by those skilled in the art, and refers to a method of analyzing the presence or identity (identity) of a double-stranded nucleic acid molecule by determining the melting curve of the double-stranded nucleic acid molecule, which is commonly used to assess the dissociation characteristics of the double-stranded nucleic acid molecule during heating. Methods for performing melting curve analysis are well known to those skilled in The art (see, e.g., The Journal of Molecular Diagnostics2009,11(2): 93-101). In the present application, the terms "melting curve analysis" and "melting analysis" have the same meaning and are used interchangeably.

In certain preferred embodiments of the present application, the melting curve analysis may be performed by using a detection probe labeled with a reporter group and a quencher group. Briefly, at ambient temperature, the detection probe is capable of forming a duplex with its complementary sequence by base pairing. In this case, the reporter (e.g., fluorophore) and the quencher on the detection probe are separated from each other, and the quencher cannot absorb a signal (e.g., a fluorescent signal) emitted from the reporter, and at this time, the strongest signal (e.g., a fluorescent signal) can be detected. As the temperature is increased, both strands of the duplex begin to dissociate (i.e., the detection probe gradually dissociates from its complementary sequence), and the dissociated detection probe is in a single-stranded free coiled-coil state. In this case, the reporter (e.g., fluorophore) and the quencher on the detection probe under dissociation are brought into close proximity to each other, whereby a signal (e.g., a fluorescent signal) emitted from the reporter (e.g., fluorophore) is absorbed by the quencher. Thus, as the temperature increases, the detected signal (e.g., the fluorescence signal) becomes progressively weaker. When both strands of the duplex are completely dissociated, all detection probes are in a single-stranded free coiled-coil state. In this case, the signal (e.g., fluorescent signal) from the reporter (e.g., fluorophore) on all of the detection probes is absorbed by the quencher. Thus, a signal (e.g., a fluorescent signal) emitted by a reporter (e.g., a fluorophore) is substantially undetectable. Thus, by detecting the signal (e.g., fluorescent signal) emitted by the duplex containing the detection probe during the temperature increase or decrease, the hybridization and dissociation processes of the detection probe and its complementary sequence can be observed, forming a curve whose signal intensity varies with temperature. Further, by performing derivative analysis on the obtained curve, a curve (i.e., melting curve of the duplex) is obtained with the rate of change of signal intensity as ordinate and the temperature as abscissa. The peak in the melting curve is the melting peak, which is the oppositeThe temperature at which this occurs is the melting point (T) of the duplex_mValue). In general, the higher the degree of match of the detection probe to the complementary sequence (e.g., the fewer mismatched bases, the more bases paired), the T of the duplex_mThe higher the value. Thus, by detecting T of the duplex_mValue, the presence and identity of the sequence in the duplex that is complementary to the detection probe can be determined. As used herein, the terms "melting peak", "melting point" and "T_mThe value "has the same meaning and is used interchangeably.

In the present application, the inventors developed a novel real-time PCR assay method that can distinguish and identify a plurality of target sequences in a sample with a simpler reaction system and at a lower detection cost. On the basis, the inventor of the application develops a method and a kit which are more rapid, simple, sensitive, specific, stable and reliable and can simultaneously detect a plurality of bacterial serotypes (such as Escherichia coli O serotype, Escherichia coli H serotype, Escherichia coli K serotype, Salmonella O serotype, Salmonella H serotype, Vibrio parahaemolyticus O serotype, Vibrio parahaemolyticus K serotype, Shigella O serotype, Vibrio cholerae O serotype and the like). For example, the methods and kits of the invention are capable of simultaneously detecting 2, 3, 4, 5,6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more bacterial serotypes.

Detection method

Accordingly, in one aspect, the present invention provides a method of detecting the presence of at least two bacterial serotypes in a sample, wherein the method comprises the steps of:

(1) contacting the sample with a first upstream oligonucleotide sequence, a first mediator probe, a second upstream oligonucleotide sequence, and a second mediator probe under conditions that allow for nucleic acid hybridization,

(i) the first upstream oligonucleotide sequence comprises a sequence complementary to a first target nucleic acid sequence; and, the first mediator probe comprises, in the 5 'to 3' direction, a first mediator subsequence comprising a sequence that is not complementary to the first target nucleic acid sequence and a first target-specific sequence comprising a sequence that is complementary to the first target nucleic acid sequence; and, when hybridized to the first target nucleic acid sequence, the first upstream oligonucleotide sequence is located upstream of the first target-specific sequence; wherein the first target nucleic acid sequence is specific for a first bacterial serotype, preferably a gene sequence for an antigen of the first bacterial serotype, or a specific fragment thereof;

(ii) the second upstream oligonucleotide sequence comprises a sequence complementary to a second target nucleic acid sequence; and, the second mediator probe comprises, in the 5 'to 3' direction, a second mediator subsequence comprising a sequence that is not complementary to the second target nucleic acid sequence and a second target-specific sequence comprising a sequence that is complementary to the second target nucleic acid sequence; and, when hybridized to a second target nucleic acid sequence, a second upstream oligonucleotide sequence is located upstream of the second target-specific sequence; wherein the second target nucleic acid sequence is specific for a second bacterial serotype, preferably a gene sequence for an antigen of the second bacterial serotype, or a specific fragment thereof; and the number of the first and second electrodes,

(iii) the first intermediary subsequence is different from the second intermediary subsequence; and the number of the first and second electrodes,

(2) contacting the product of step (1) with an enzyme having 5' nuclease activity under conditions that allow cleavage of the mediator probe;

(3) contacting the product of step (2) with a detection probe comprising, in the 3 'to 5' direction, a first capture sequence complementary to the first mediator sequence or a portion thereof, a second capture sequence complementary to the second mediator sequence or a portion thereof, and a template sequence (templating sequence) under conditions permitting nucleic acid hybridization; and the number of the first and second electrodes,

the detection probe is marked with a reporter group and a quenching group, wherein the reporter group can emit a signal, and the quenching group can absorb or quench the signal emitted by the reporter group; and wherein the detection probe emits a signal when hybridized to its complement that is different from the signal when not hybridized to its complement;

(4) contacting the product of step (3) with a nucleic acid polymerase under conditions that allow the nucleic acid polymerase to perform an extension reaction;

(5) performing melting curve analysis on the product obtained in the step (4); and determining whether the first and second target nucleic acid sequences are present in the sample based on the results of the melting curve analysis, thereby determining whether the first and second bacterial serotypes are present in the sample.

In certain preferred embodiments, the first bacterial serotype or the second bacterial serotype may be selected from the group consisting of escherichia coli serotype O, escherichia coli serotype H, escherichia coli serotype K, salmonella serotype O, salmonella serotype H, vibrio parahaemolyticus serotype O, vibrio parahaemolyticus serotype K, shigella serotype O, vibrio cholerae serotype O, and the like.

In the methods of the invention, since the first target nucleic acid sequence is specific for a first bacterial serotype and the second target nucleic acid sequence is specific for a second bacterial serotype, respectively, the presence of the first bacterial serotype and the second bacterial serotype can be determined by detecting the presence of the first target nucleic acid sequence and the second target nucleic acid sequence.

As used herein, the expression "a target nucleic acid sequence is specific for a bacterial serotype" means that the target nucleic acid sequence is specific for the bacterial serotype and is not present in other bacterial serotypes, including other serotypes of the same species and other bacteria. In other words, the target nucleic acid sequence can only be detected in the bacterial serotype, whereby the presence of the target nucleic acid sequence is indicative of the presence of the bacterial serotype and vice versa. A typical example of such target nucleic acid sequences include, but are not limited to, antigenic gene sequences of the bacterial serotype, or specific fragments thereof. As used herein, the expression "a fragment specific for an antigenic gene sequence of a bacterial serotype" has a similar meaning, i.e. the fragment is unique to the serotype bacterium and its antigen. Such specific fragments can be non-coding sequences (e.g., sequences that do not encode any RNA or protein), or coding sequences (e.g., sequences capable of being transcribed or translated), or a combination of both, so long as they are serotype specific.

Whether a nucleic acid sequence or a fragment is serotype specific for a bacterium can be determined by a variety of well-known methods. For example, it can be determined whether the nucleic acid sequence is specific for a particular bacterial serotype by performing a Blast search of the nucleic acid sequence in a public database (e.g., the NCBI database).

In step (1) of the method of the invention, since the first upstream oligonucleotide sequence comprises a sequence complementary to the first target nucleic acid sequence and the first target-specific sequence comprises a sequence complementary to the first target nucleic acid sequence, both the first upstream oligonucleotide sequence and the first mediator probe hybridize to the first target nucleic acid sequence when present. Similarly, since the second upstream oligonucleotide sequence comprises a sequence complementary to a second target nucleic acid sequence and the second target-specific sequence comprises a sequence complementary to the second target nucleic acid sequence, both the second upstream oligonucleotide sequence and the second mediator probe hybridize to the second target nucleic acid sequence when present.

In step (2) of the method of the invention, the first upstream oligonucleotide sequence and the first mediator probe both hybridize to a first target nucleic acid sequence when present. Further, since the first mediator sequence includes a sequence that is not complementary to the first target nucleic acid sequence, the first mediator sequence in the first mediator probe is in an episomal state and does not hybridize to the first target nucleic acid sequence. In this case, under the action of the enzyme having 5' nuclease activity, the first mediator sequence or a portion thereof is cleaved from the first mediator probe hybridized with the first target nucleic acid sequence by the presence of the first upstream oligonucleotide sequence or an extension product thereof, to form a first mediator fragment. Similarly, when the second target nucleic acid sequence is present, both the second upstream oligonucleotide sequence and the second mediator probe hybridize to the second target nucleic acid sequence, and the second mediator sequence in the second mediator probe is in a free state and does not hybridize to the second target nucleic acid sequence. In this case, the second mediator sequence or a portion thereof is cleaved from the second mediator probe hybridized to the second target nucleic acid sequence by the presence of the second upstream oligonucleotide sequence or its extension product under the action of the enzyme having 5' nuclease activity to form a second mediator fragment.

In step (3) of the method of the invention, when the first mediator fragment is present, the first mediator fragment hybridises to the detection probe in that the first mediator fragment comprises a first mediator subsequence or portion thereof and the detection probe comprises a first capture sequence complementary to the first mediator subsequence or portion thereof. Similarly, when a second mediator segment is present, it hybridizes to the detection probe as it comprises a second mediator subsequence, or portion thereof, and the detection probe comprises a second capture sequence that is complementary to the second mediator subsequence, or portion thereof.

In step (4) of the method of the invention, when a first mediator fragment is present, the nucleic acid polymerase will extend the first mediator fragment, using the detection probe as a template, to form a first duplex, since the first mediator fragment hybridises to the detection probe and the detection probe comprises an additional sequence (e.g. a template sequence). Similarly, when a second mediator segment is present, the nucleic acid polymerase will extend the second mediator segment to form a second duplex using the detection probe as a template, since the second mediator segment hybridizes to the detection probe and the detection probe comprises additional sequences (e.g., a template sequence).

In step (5) of the method of the present invention, when the first duplex is present, a melting peak corresponding to the first duplex can be detected. Thus, the presence or absence of the first target nucleic acid sequence in the sample can be determined by the presence or absence of a melting peak corresponding to the first duplex. For example, determining the presence or absence of a first target nucleic acid sequence in the sample when a melting peak corresponding to the first duplex is detected or not detected; further, since the first target nucleic acid sequence is specific for the first bacterial serotype, it can be determined whether the first bacterial serotype is present or absent in the sample. Similarly, the presence or absence of the second target nucleic acid sequence in the sample can be determined by the presence or absence of a melting peak corresponding to the second duplex. For example, determining the presence or absence of a second target nucleic acid sequence in the sample when a melting peak corresponding to a second duplex is detected or not detected; further, since the second target nucleic acid sequence is specific for the second bacterial serotype, it can be determined whether the second bacterial serotype is present or absent in the sample.

In particular, in the method of the present invention, since the first mediator sub-sequence and the second mediator sub-sequence used are different, the first mediator fragment and the second mediator fragment formed have different sequences and hybridize to different positions of the detection probe. Thus, the first duplex comprising the extension product of the first mediator segment and the detection probe is also different in structure (sequence) from the second duplex comprising the extension product of the second mediator segment and the detection probe. Accordingly, the first duplex will have a different melting point (T) than the second duplex_mValue). Thus, in melting curve analysis, the first duplex shows a melting peak different from that of the second duplex. Thus, by detecting the melting peak of the first duplex or the second duplex, the presence of the first target nucleic acid sequence or the second target nucleic acid sequence in the sample can be determined.

In addition, since the sequences of the first mediator sequence, the second mediator sequence, and the detection probe are known or predetermined, the melting points (T) of the first duplex and the second duplex can be calculated in advance_mValue). Thus, the melting point (T) of the first duplex or the second duplex is detected by melting curve analysis_mValue), the presence of the first target nucleic acid sequence or the second target nucleic acid sequence in the sample can be determined.

Based on the same principle as described above, the method of the present invention can be used to simultaneously detect more target nucleic acid sequences by designing more mediator probes, and thus can be used to detect, for example, more serotypes of bacteria. Thus, in certain preferred embodiments, in step (1), the sample is contacted with a third upstream oligonucleotide sequence and a third mediator probe under conditions that allow nucleic acid hybridization in addition to the first upstream oligonucleotide sequence, the first mediator probe, the second upstream oligonucleotide sequence, and the second mediator probe, wherein,

the third upstream oligonucleotide sequence comprises a sequence complementary to a third target nucleic acid sequence; and, the third mediator probe comprises, in the 5 'to 3' direction, a third mediator subsequence comprising a sequence that is not complementary to the third target nucleic acid sequence and a third target-specific sequence comprising a sequence that is complementary to the third target nucleic acid sequence; wherein the third target nucleic acid sequence is specific for a third bacterial serotype, e.g., the third bacterial serotype can be selected from the group consisting of escherichia coli serotype O, escherichia coli serotype H, escherichia coli serotype K, salmonella serotype O, salmonella serotype H, vibrio parahaemolyticus serotype O, vibrio parahaemolyticus serotype K, shigella serotype O, vibrio cholerae serotype O, and the like; preferably, the third target nucleic acid sequence is an antigenic gene sequence of a third bacterial serotype, or a specific fragment thereof;

and, when hybridized to a third target nucleic acid sequence, the third upstream oligonucleotide sequence is upstream of the third target-specific sequence; and, the third intermediary subsequence is different from the first and second intermediary subsequences;

and, in step (3), the detection probe used further comprises a third capture sequence complementary to a third mediator sequence, or a portion thereof, downstream of the template sequence.

In such embodiments, in step (1), the third upstream oligonucleotide sequence and the third mediator probe hybridize to a third target nucleic acid sequence when present. Further, in step (2), when the third target nucleic acid sequence is present, the third mediator sequence or a portion thereof is cleaved from the third mediator probe hybridized with the third target nucleic acid sequence by the presence of the third upstream oligonucleotide sequence or an extension product thereof, to form a third mediator fragment. Further, in steps (3) and (4), when a third mediator fragment is present, it hybridizes to the detection probe and the nucleic acid polymerase will extend the third mediator fragment using the detection probe as a template to form a third duplex. Further, in step (5), when a melting peak corresponding to the third duplex is detected or not detected, it is determined that the third target nucleic acid sequence is present or absent in the sample. Still further, since the third target nucleic acid sequence is specific for a third bacterial serotype, it can be determined whether the third bacterial serotype is present or absent in the sample.

Similarly, in the method of the invention, the first mediator fragment, the second mediator fragment and the third mediator fragment are formed to have different sequences and hybridize to different positions of the detection probe, due to the difference in the first, second and third mediator sequences used. Thus, the first duplex comprising the extension product of the first mediator fragment and the detection probe, the second duplex comprising the extension product of the second mediator fragment and the detection probe, and the third duplex comprising the extension product of the third mediator fragment and the detection probe differ from each other in structure (sequence). Accordingly, the first, second and third duplexes have melting points (T) different from each other_mValue). Thus, in melt curve analysis, the first, second and third duplexes exhibit three melt peaks that are distinguishable from each other. Thus, by detecting melting peaks of the first, second and third duplexes, the presence of the first, second and third target nucleic acid sequences in the sample can be determined.

In addition, since the sequences of the first, second, and third mediator sequences and the detection probe are known or predetermined, the melting points (T) of each of the first, second, and third duplexes can be pre-calculated_mValue). Whereby melting points of the first, second or third duplexes are detected by melting curve analysis(T_mValue) of the first, second, or third target nucleic acid sequence in the sample.

In certain preferred embodiments, in step (1), the sample is contacted with a fourth upstream oligonucleotide sequence and a fourth mediator probe, in addition to the first upstream oligonucleotide sequence, the first mediator probe, the second upstream oligonucleotide sequence, the second mediator probe, the third upstream oligonucleotide sequence, and the third mediator probe, wherein,

the fourth upstream oligonucleotide sequence comprises a sequence complementary to a fourth target nucleic acid sequence; and, the fourth mediator probe comprises, in the 5 'to 3' direction, a fourth mediator subsequence comprising a sequence that is not complementary to a fourth target nucleic acid sequence and a fourth target-specific sequence comprising a sequence that is complementary to a fourth target nucleic acid sequence; wherein the fourth target nucleic acid sequence is specific for a fourth bacterial serotype, e.g., the fourth bacterial serotype is selected from the group consisting of escherichia coli serotype O, escherichia coli serotype H, escherichia coli serotype K, salmonella serotype O, salmonella serotype H, vibrio parahaemolyticus serotype O, vibrio parahaemolyticus serotype K, shigella serotype O, vibrio cholerae serotype O, and the like; preferably, the fourth target nucleic acid sequence is an antigenic gene sequence of a fourth bacterial serotype, or a specific fragment thereof;

and, when hybridized to a fourth target nucleic acid sequence, a fourth upstream oligonucleotide sequence is located upstream of the fourth target-specific sequence; and, the fourth intermediary subsequence is different from the first, second, and third intermediary subsequences;

and, in step (3), the detection probe used further comprises a fourth capture sequence complementary to a fourth mediator sequence, or a portion thereof, downstream of the template sequence.

In such embodiments, in step (1), when a fourth target nucleic acid sequence is present, the fourth upstream oligonucleotide sequence and the fourth mediator probe hybridize to the fourth target nucleic acid sequence. Further, in step (2), when a fourth target nucleic acid sequence is present, a fourth mediator sequence or a portion thereof is cleaved from the fourth mediator probe hybridized with the fourth target nucleic acid sequence by the presence of the fourth upstream oligonucleotide sequence or an extension product thereof, to form a fourth mediator fragment. Further, in steps (3) and (4), when a fourth mediator fragment is present, it hybridizes to the detection probe, and the nucleic acid polymerase will extend the fourth mediator fragment using the detection probe as a template to form a fourth duplex. Further, in step (5), when a melting peak corresponding to the fourth duplex is detected or not detected, it is determined that the fourth target nucleic acid sequence is present or absent in the sample. Still further, since the fourth target nucleic acid sequence is specific for a fourth bacterial serotype, it can be determined whether the fourth bacterial serotype is present or absent in the sample.

Similarly, in the method of the present invention, the first mediator segment, the second mediator segment, the third mediator segment and the fourth mediator segment are formed to have different sequences and hybridize to different positions of the detection probe, since the first, second, third and fourth mediator sequences used are different. Thus, the first duplex comprising the extension product of the first mediator fragment and the detection probe, the second duplex comprising the extension product of the second mediator fragment and the detection probe, the third duplex comprising the extension product of the third mediator fragment and the detection probe, the fourth duplex comprising the extension product of the fourth mediator fragment and the detection probe differ from each other in structure (sequence). Accordingly, the first, second, third and fourth duplexes have melting points (T) different from each other_mValue). Thus, in melt curve analysis, the first, second, third and fourth duplexes exhibit four melt peaks that are distinguishable from each other. Thus, by detecting melting peaks of the first, second, third and fourth duplexes, the presence of the first, second, third and fourth target nucleic acid sequences in the sample can be determined.

In addition, since the sequences of the first, second, third and fourth mediator sequences and the detection probe are known or predeterminedThus, the melting points (T) of each of the first, second, third and fourth duplexes may be pre-calculated_mValue). Thus, by detecting the melting point (T) of the duplex having the first, second, third or fourth duplex in a melting curve analysis_mValue) of the first, second, third or fourth target nucleic acid sequence in the sample.

Similarly, more upstream oligonucleotide sequences and more mediator probes may be used to carry out the methods of the invention. For example, in certain embodiments, the methods of the invention can be practiced using at least 5 upstream oligonucleotide sequences, at least 5 mediator probes, and a detection probe, wherein,

each upstream oligonucleotide sequence comprises a sequence complementary to a target nucleic acid sequence; and the number of the first and second electrodes,

each mediator probe comprises a mediator sequence and a target specific sequence from 5 'to 3', wherein the mediator sequence comprises a sequence that is not complementary to a target nucleic acid sequence, and the target specific sequence comprises a sequence that is complementary to a target nucleic acid sequence; thus, when a target nucleic acid sequence is present, both the upstream oligonucleotide sequence corresponding to the target nucleic acid sequence and the mediator probe are capable of hybridizing to the target nucleic acid sequence; and, when hybridized to the target nucleic acid sequence, the upstream oligonucleotide sequence is upstream of the target-specific sequence of the mediator probe; and, all the mediator subsequences contained in the mediator probe are different from each other; and, each target nucleic acid sequence is specific for a respective bacterial serotype. Preferably, each bacterial serotype may be each independently selected from escherichia coli O serotype, escherichia coli H serotype, escherichia coli K serotype, salmonella O serotype, salmonella H serotype, vibrio parahaemolyticus O serotype, vibrio parahaemolyticus K serotype, shigella O serotype, vibrio cholerae O serotype, and the like, and the detection probe comprises a template sequence, and a plurality of sequences located downstream of the template sequence and respectively complementary to the mediator sequence or a portion thereof in each mediator sub-probe. In such embodiments, the methods of the invention can be used to simultaneously detect at least 5 target nucleic acid sequences.

In certain embodiments, the methods of the invention can employ at least 6 upstream oligonucleotide sequences, at least 6 mediator probes, and a detection probe; preferably, at least 7 upstream oligonucleotide sequences, at least 7 mediator probes and a detection probe; preferably, at least 8 upstream oligonucleotide sequences, at least 8 mediator probes and a detection probe; preferably, at least 9 upstream oligonucleotide sequences, at least 9 mediator probes and a detection probe; preferably, at least 10 upstream oligonucleotide sequences, at least 10 mediator probes and a detection probe; preferably, at least 12 upstream oligonucleotide sequences, at least 12 mediator probes and a detection probe; preferably, at least 15 upstream oligonucleotide sequences, at least 15 mediator probes and a detection probe; preferably, at least 20 upstream oligonucleotide sequences, at least 20 mediator probes and a detection probe; wherein the upstream oligonucleotide sequence, mediator probe and detection probe are as defined above. In such embodiments, the methods of the invention can be used to simultaneously detect at least 6, at least 7, at least 8, at least 9, at least 10, at least 12, at least 15, at least 19, or at least 20 target nucleic acid sequences or bacterial serotypes. Preferably, each bacterial serotype is each independently selected from the group consisting of escherichia coli O serotype, escherichia coli H serotype, escherichia coli K serotype, salmonella O serotype, salmonella H serotype, vibrio parahaemolyticus O serotype, vibrio parahaemolyticus K serotype, shigella O serotype, vibrio cholerae O serotype, and the like.

Thus, in certain embodiments, the invention provides a method of detecting the presence of n bacterial serotypes in a sample, wherein n is an integer ≧ 2 (e.g., n is an integer of 2, 3, 4, 5,6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more), and the method comprises the steps of:

(1) for each bacterial serotype to be detected, determining at least one target nucleic acid sequence specific for that bacterial serotype; then, for each target nucleic acid sequence, providing an upstream oligonucleotide sequence and a mediator probe; wherein the upstream oligonucleotide sequence comprises a sequence complementary to the target nucleic acid sequence; and, the mediator probe comprises, in the 5 'to 3' direction, a mediator subsequence comprising a sequence that is not complementary to the target nucleic acid sequence and a target-specific sequence comprising a sequence that is complementary to the target nucleic acid sequence; and, when hybridized to the target nucleic acid sequence, the upstream oligonucleotide sequence is upstream of the target-specific sequence; and, all the mediator subsequences contained in the mediator probe are different from each other;

and, contacting the sample with the provided upstream oligonucleotide sequences and mediator probes under conditions that allow nucleic acid hybridization;

(3) contacting the product of step (2) with a detection probe comprising, in the 3 'to 5' direction, a capture sequence complementary to each of the mediator sequences or parts thereof, and a template sequence (templating sequence), under conditions permitting nucleic acid hybridization; and the detection probe is labeled with a reporter group and a quencher group, wherein the reporter group can emit a signal, and the quencher group can absorb or quench the signal emitted by the reporter group; and wherein the detection probe emits a signal when hybridized to its complement that is different from the signal when not hybridized to its complement;

(5) performing melting curve analysis on the product obtained in the step (4); and determining whether each target nucleic acid sequence is present in the sample and, in turn, whether the bacterial serotype corresponding to each target nucleic acid sequence is present in the sample based on the results of the melting curve analysis.

In certain preferred embodiments, each target is independently selected from the group consisting of serotype E.coli O, serotype H E.coli, serotype K E.coli, serotype O Salmonella, serotype H Salmonella, serotype O Vibrio parahaemolyticus, serotype K Vibrio parahaemolyticus, serotype O Shigella, serotype O Vibrio cholerae, and the like.

In step (1) of such embodiments, when a target nucleic acid sequence is present, both the upstream oligonucleotide sequence corresponding to the target nucleic acid sequence (i.e., the upstream oligonucleotide sequence comprising a sequence complementary to the target nucleic acid sequence) and the mediator probe corresponding to the target nucleic acid sequence (i.e., the mediator probe whose target-specific sequence comprises a sequence complementary to the target nucleic acid sequence) hybridize to the target nucleic acid sequence.

Further, in step (2) of such embodiments, when a target nucleic acid sequence is present, the upstream oligonucleotide sequence corresponding to the target nucleic acid sequence and the mediator probe hybridize to the target nucleic acid sequence, but the mediator sequence in the mediator probe is in a free state and does not hybridize to the target nucleic acid sequence. In this case, under the action of an enzyme having 5' nuclease activity, the mediator sequence or a part thereof in the mediator probe (the mediator probe corresponding to the target nucleic acid sequence) is cleaved from the mediator probe by the presence of the upstream oligonucleotide sequence corresponding to the target nucleic acid sequence or an extension product thereof, to form a mediator fragment corresponding to the target nucleic acid sequence.

Further, in steps (3) and (4) of such embodiments, when a mediator fragment corresponding to a certain target nucleic acid sequence is present, the mediator fragment hybridizes to the detection probe, and the nucleic acid polymerase will extend the mediator fragment using the detection probe as a template to form a duplex corresponding to the target nucleic acid sequence. Still further, in step (5) of such embodiments, when a melting peak of a duplex corresponding to a certain target nucleic acid sequence is detected or not detected, the presence or absence of the target nucleic acid sequence in the sample is determined, and thereby the presence or absence of a bacterial serotype corresponding to the target nucleic acid sequence in the sample is determined.

In particular, in such embodiments, since all mediator probes used contain different mediator sequences from each other, each mediator fragment formed has a different sequence and hybridizes to a different position of the detection probe. Thus, each duplex consisting of the extension product of the mediator fragment and the detection probe has a structure (sequence) different from each other. Accordingly, each of the duplexes has a melting point (T) different from each other_mValue). Thus, in melting curve analysis, each duplex shows a melting peak that is different from each other. Thus, by detecting the melting peak of a certain duplex, the presence of the target nucleic acid sequence corresponding to the duplex in the sample can be determined.

In addition, since the sequence of each mediator subsequence, as well as the sequence of the detection probe, are known or predetermined, the respective melting points (T) of each duplex can be pre-calculated_mValue). Thus, by detecting the melting point (T) of a duplex in a melting curve analysis_mValue) to determine the presence of a target nucleic acid sequence corresponding to the duplex in the sample.

Having briefly summarized the basic principles of the method of the present invention, reference will now be made in detail to the steps of the method of the present invention, which are illustrated and exemplified.

Concerning the steps (1) and (2)

In the methods of the invention, a target nucleic acid sequence (e.g., a first or second target nucleic acid sequence; if present) specific for a bacterial serotype in a sample is first hybridized to a corresponding upstream oligonucleotide sequence (e.g., a first or second upstream oligonucleotide sequence) and a corresponding mediator probe (e.g., a first or second mediator probe).

In the method of the present invention, the sample may be any sample to be detected. For example, in certain preferred embodiments, the sample comprises or is DNA (e.g., genomic DNA or cDNA). In certain preferred embodiments, the sample comprises or is RNA (e.g., mRNA). In certain preferred embodiments, the sample comprises or is a mixture of nucleic acids (e.g., a mixture of DNA, a mixture of RNA, or a mixture of DNA and RNA). In certain preferred embodiments, the sample to be detected is a sample obtained from a subject, e.g., stool, anal swab, bacterial culture, and the like. In certain preferred embodiments, the subject is a mammal, e.g., a primate, e.g., a human.

In the method of the present invention, the target nucleic acid sequence to be detected is not limited to its sequence composition or length. For example, the target nucleic acid sequence may be a DNA (e.g., genomic DNA or cDNA) or an RNA molecule (e.g., mRNA). In addition, the target nucleic acid sequence to be detected may be single-stranded or double-stranded.

When the sample or target nucleic acid sequence to be detected is mRNA, preferably, a reverse transcription reaction is performed to obtain cDNA complementary to the mRNA prior to performing the method of the present invention. For a detailed description of the reverse transcription reaction, see, for example, Joseph Sam-brook, et al, Molecular Cloning, A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. (2001).

The sample or target nucleic acid sequence to be detected can be obtained from any source. In the methods of the invention, the sample to be tested is a sample containing or suspected of containing a bacterial serotype. In certain preferred embodiments, the bacterial serotype is selected from the group consisting of escherichia coli serotype O, escherichia coli serotype H, escherichia coli serotype K, salmonella serotype O, salmonella serotype H, vibrio parahaemolyticus serotype O, vibrio parahaemolyticus serotype K, shigella serotype O, vibrio cholerae serotype O, and the like. In certain exemplary embodiments, the bacterial serotype is selected from the group consisting of e.coli type O29, e.coli type O29, e.coli type O26, e.coli type O169, e.coli type O161, e.coli type O126, e.coli type O8, e.coli type O143, e.coli type O1, e.coli type O157, e.coli type O148, e.coli type O27, e.coli type O167, e.coli type O6, e.coli type Gp6, e.coli type O15, e.coli type O159, e.coli type Gp12, e.coli type O25, e.coli type O166, e.coli type O91, e.coli type Gp2, e.coli type O86, e.coli type O111, e.coli type O121, e.coli type O145, e.coli type O55, e.coli type Gp9, e.coli type O63, e.coli type O18, e.coli type O128, e.coli type O, Escherichia coli O113, Escherichia coli O104, Escherichia coli O45, Escherichia coli O142, or any combination thereof. It is readily understood that in the method of the present invention, the bacterial serotype is not limited to the type described, but may be any serotype of any bacterium, such as Escherichia coli O5, Escherichia coli O7, Salmonella O1, Salmonella O5, Vibrio cholerae O1, Vibrio cholerae O139, Vibrio parahaemolyticus O1, Vibrio parahaemolyticus O3, Listeria O1, Listeria O4, and the like. The sample or target nucleic acid sequence to be detected may also be any form of nucleic acid sequence, such as genomic sequences, artificially isolated or fragmented sequences, synthetic sequences, and the like.

In certain embodiments of the invention, the at least one bacterial serotype is selected from the group consisting of escherichia coli serotype O, escherichia coli serotype H, escherichia coli serotype K, salmonella serotype O, salmonella serotype H, vibrio parahaemolyticus serotype O, vibrio parahaemolyticus serotype K, shigella serotype O, vibrio cholerae serotype O, and the like.

In certain embodiments of the invention, the mediator probe may comprise or consist of naturally occurring nucleotides (e.g., deoxyribonucleotides or ribonucleotides), modified nucleotides, non-natural nucleotides, or any combination thereof.

In the method of the present invention, the mediator sub-probes are not limited by their length. For example, the length of the mediator probe may be 15-1000nt, such as 15-20nt, 20-30nt, 30-40nt, 40-50nt, 50-60nt, 60-70nt, 70-80nt, 80-90nt, 90-100nt, 100-200nt, 200-300nt, 300-400nt, 400-500nt, 500-600nt, 600-700nt, 700-800nt, 800-900nt, 900-1000 nt. For example, the length of the mediator probe may be 15-150nt, such as 15-20nt, 20-30nt, 30-40nt, 40-50nt, 50-60nt, 60-70nt, 70-80nt, 80-90nt, 90-100nt, 100 + 110nt, 110 + 120nt, 120 + 130nt, 130 + 140nt, 140 + 150 nt. The target-specific sequence in the mediator probe may be of any length as long as it is capable of specifically hybridizing to the target nucleic acid sequence. For example, the length of the target-specific sequence in the mediator probe may be 10-500nt, such as 10-20nt, 20-30nt, 30-40nt, 40-50nt, 50-60nt, 60-70nt, 70-80nt, 80-90nt, 90-100nt, 100-150nt, 150-200nt, 200-250nt, 250-300nt, 300-350nt, 350-400nt, 400-450nt, 450-500 nt. For example, the length of the target-specific sequence in the mediator probe may be 10-140nt, such as 10-20nt, 20-30nt, 30-40nt, 40-50nt, 50-60nt, 60-70nt, 70-80nt, 80-90nt, 90-100nt, 100-110nt, 110-120nt, 120-130nt, 130-140 nt. The mediator sequence in the mediator probe may be of any length as long as it is capable of specifically hybridizing to and extending the detection probe. For example, the length of the mediator sequence in the mediator probe may be 5-140nt, such as 5-10nt, 8-50nt, 8-15nt, 15-20nt, 10-20nt, 20-30nt, 30-40nt, 40-50nt, 50-60nt, 60-70nt, 70-80nt, 80-90nt, 90-100nt, 100 + 110nt, 110 + 120nt, 120 + 130nt, 130 + 140 nt. In certain preferred embodiments, the target-specific sequence in the mediator probe is 10-100nt (e.g., 10-90nt, 10-80nt, 10-50nt, 10-40nt, 10-30nt, 10-20nt) in length, and the mediator sequence is 5-100nt (e.g., 10-90nt, 10-80nt, 10-50nt, 10-40nt, 10-30nt, 10-20nt) in length.

In certain preferred embodiments, the mediator probe has a 3' -OH terminus. In certain preferred embodiments, the 3' -end of the mediator probe is blocked to inhibit extension thereof. The 3' -end of a nucleic acid (e.g., a mediator probe) can be blocked by various methods. For example, the 3 '-end of the mediator probe may be blocked by modifying the 3' -OH of the last nucleotide of the mediator probe. In certain embodiments, the 3 '-end of the mediator probe may be blocked by adding a chemical moiety (e.g., biotin or alkyl) to the 3' -OH of the last nucleotide of the mediator probe. In certain embodiments, the 3 '-end of the mediator probe may be blocked by removing the 3' -OH of the last nucleotide of the mediator probe, or replacing the last nucleotide with a dideoxynucleotide.

In certain embodiments of the invention, the upstream oligonucleotide sequence may comprise or consist of naturally occurring nucleotides (e.g., deoxyribonucleotides or ribonucleotides), modified nucleotides, non-natural nucleotides, or any combination thereof.

In the method of the present invention, the upstream oligonucleotide sequence is not limited by its length as long as it can specifically hybridize to the target nucleic acid sequence. For example, the length of the upstream oligonucleotide sequence may be 15-150nt, such as 15-20nt, 20-30nt, 30-40nt, 40-50nt, 50-60nt, 60-70nt, 70-80nt, 80-90nt, 90-100nt, 100-110nt, 110-120nt, 120-130nt, 130-140nt, 140-150 nt.

In the method of the present invention, conditions allowing nucleic acid hybridization can be routinely determined by one skilled in the art. For example, suitable hybridization conditions can be determined based on the target nucleic acid sequence to be detected, the upstream oligonucleotide sequence used, and the target-specific sequence in the mediator probe. In certain embodiments of the invention, the conditions that allow nucleic acid hybridization are stringent conditions such that the target-specific sequence in the upstream oligonucleotide sequence and the mediator sub-probe hybridize to the corresponding target nucleic acid sequence by base-complementary pairing, and the mediator sub-sequence in the mediator sub-probe does not hybridize to the target nucleic acid sequence. In certain preferred embodiments, the sample is contacted with various upstream oligonucleotide sequences and various mediator probes under high stringency conditions.

In the methods of the invention, after contacting the sample with the various upstream oligonucleotide sequences and the various mediator probes, it is necessary to induce cleavage of the mediator probes to release fragments containing the mediator sequences or portions thereof (i.e., mediator fragments). In general, cleavage of a mediator probe hybridized to a target nucleic acid sequence can be induced using an enzyme having 5' nuclease activity, using an upstream oligonucleotide sequence hybridized to the target nucleic acid sequence or an extension product thereof. Specifically, in step (1), when the mediator probe is contacted with the target nucleic acid sequence, the mediator probe comprises a target-specific sequence that hybridizes to the target nucleic acid sequence and forms a double-stranded structure, while the mediator probe does not hybridize to the target nucleic acid sequence and maintains a single-stranded structure. Thus, such oligonucleotides comprising a double-stranded structure and a single-stranded structure can be cleaved with an enzyme having 5' nuclease activity, and fragments having a single-stranded structure are released.

It will be readily appreciated that in the method of the invention, the upstream oligonucleotide sequence and the mediator probe will hybridize to the same strand of the target nucleic acid sequence under conditions which permit nucleic acid hybridization, and the upstream oligonucleotide sequence is located upstream of the mediator probe, thereby inducing cleavage of the mediator probe. In certain embodiments of the invention, cleavage of the mediator probe may be induced in two ways: (A) a manner of extension independent of the upstream oligonucleotide sequence; and (B) a manner of extension dependent on the upstream oligonucleotide sequence. In particular, if the upstream oligonucleotide sequence and mediator probe are sufficiently close together that an enzyme having 5' nuclease activity is able to induce cleavage of the mediator probe after hybridization of the upstream oligonucleotide sequence and mediator probe to the target nucleic acid sequence, the enzyme will bind to the upstream oligonucleotide sequence and cleave the mediator probe without performing an extension reaction (i.e., mode a). Conversely, if the upstream oligonucleotide sequence is remote from the mediator probe after hybridization to the target nucleic acid sequence, then a nucleic acid polymerase is used to catalyze extension of the upstream oligonucleotide sequence using the target nucleic acid sequence as a template, followed by an enzyme with 5' nuclease activity that binds to the extension product of the upstream oligonucleotide sequence and cleaves the mediator probe (i.e., mode B).

Thus, in certain preferred embodiments, the upstream oligonucleotide sequence is located in upstream proximity to the mediator probe after hybridization to the target nucleic acid sequence. In such embodiments, the upstream oligonucleotide sequence directly induces the enzyme cleavage mediator probe with 5' nuclease activity without the need for an extension reaction. Thus, in such embodiments, the upstream oligonucleotide sequence is an upstream probe specific for the target nucleic acid sequence that induces cleavage of the mediator probe in an extension-independent manner. As used herein, the term "adjacent" is intended to mean that two nucleic acid sequences are adjacent to each other, forming a gap. In certain preferred embodiments, the two adjacent nucleic acid sequences (e.g., the upstream oligonucleotide sequence and the mediator probe) are separated by no more than 30nt, such as no more than 20nt, such as no more than 15nt, such as no more than 10nt, such as no more than 5nt, such as 4nt, 3nt, 2nt, 1 nt.

In certain preferred embodiments, the upstream oligonucleotide sequence has a sequence that partially overlaps the target-specific sequence of the mediator probe after hybridization to the target nucleic acid sequence. In such embodiments, the upstream oligonucleotide sequence directly induces the enzyme cleavage mediator probe with 5' nuclease activity without the need for an extension reaction. Thus, in such embodiments, the upstream oligonucleotide sequence is an upstream probe specific for the target nucleic acid sequence that induces cleavage of the mediator probe in an extension-independent manner. In certain preferred embodiments, the partially overlapping sequences are 1 to 10nt in length, e.g., 1 to 5nt, or 1 to 3 nt.

In certain preferred embodiments, the upstream oligonucleotide sequence is located upstream distal to the mediator probe after hybridization to the target nucleic acid sequence. In such embodiments, the upstream oligonucleotide sequence is extended by a nucleic acid polymerase, and the resulting extension product induces an enzyme cleavage mediator probe with 5' nuclease activity. Thus, in such embodiments, the upstream oligonucleotide sequence is a primer specific for the target nucleic acid sequence that is used to initiate the extension reaction and induce cleavage of the mediator probe in an extension-dependent manner. As used herein, the term "distal" is intended to mean that two nucleic acid sequences are distant from each other, e.g., at least 30nt, at least 50nt, at least 80nt, at least 100nt or longer.

Thus, in certain preferred embodiments, the upstream oligonucleotide sequence is a primer specific for the target nucleic acid sequence or a probe specific for the target nucleic acid sequence. The primers are adapted to induce cleavage of the mediator probe in an extension-dependent manner. The probe is adapted to induce cleavage of the mediator probe in an extension-independent manner.

Various methods of using an upstream oligonucleotide to induce cleavage of a downstream oligonucleotide (downstream probe) are known to those skilled in the art and can be used in the present invention. For a detailed description of such processes see, for example, U.S. Pat. nos. 5,210,015,5,487,972,5,691,142,5,994,069 and 7,381,532, and U.S. application No. 2008/0241838.

In certain embodiments, the cleavage site on the mediator probe is located at the junction of the mediator sequence with the target-specific sequence (i.e., the junction of the sequence that hybridizes to the target nucleic acid and the sequence that does not hybridize to the target nucleic acid). In such embodiments, cleavage of the mediator probe by the enzyme will release a fragment comprising the entire mediator sequence. In certain embodiments, the cleavage site on the mediator probe is located within the 3' -terminal region of the mediator subsequence (i.e., upstream of the 3' -terminus of the mediator subsequence, and e.g., a few nucleotides, e.g., 1-3 nucleotides, from the 3' -terminus of the mediator sequence). In such embodiments, cleavage of the mediator probe by the enzyme will release a fragment comprising a portion (the 5' -end portion) of the mediator sequence. Thus, in certain embodiments of the invention, the mediator sub-fragment comprises the entire mediator sub-sequence, or a portion (5 '-end portion) of the mediator sub-sequence, e.g., at least 5nt, at least 8nt, at least 10nt, at least 20nt, at least 30nt, at least 40nt, at least 50nt, e.g., 5-50nt, 5-10nt, 10-20nt, 20-30nt, 30-40nt, 40-50nt, of the 5' -end of the mediator sub-sequence.

In the present application, the method of the invention can be carried out using various enzymes having 5' nuclease activity. In certain preferred embodiments, the enzyme having 5 'nuclease activity is an enzyme having 5' exonuclease activity. In certain preferred embodiments, the enzyme having 5' nuclease activity is a nucleic acid polymerase (e.g., a DNA polymerase, particularly a thermostable DNA polymerase) having 5' nuclease activity (e.g., 5' exonuclease activity). In certain embodiments, the use of a nucleic acid polymerase having 5' nuclease activity is particularly advantageous because the polymerase is capable of catalyzing extension of the upstream oligonucleotide sequence with both the target nucleic acid sequence as a template and inducing cleavage of the mediator probe.

In certain preferred embodiments, the DNA polymerase having 5' nuclease activity is a thermostable DNA polymerase obtainable from various bacterial species, for example, Thermus aquaticus (Taq), Thermus thermophilus (Tth), Thermus filiformis, Thermus flavus, Thermococcus literalis, Thermus antarinanii, Thermus caldophlus, Thermus brachophilus, Thermus ositima, Thermus ruderae, Thermus xeroderma, Thermus scodothioticus, Thermus malus silmuralis, Thermus thermophilus, Thermomaritimaria, Thermomyces neopolia, Thermus neospora, Thermomyces thermophilus, Thermomyces, Thermococcus purpureus, Thermomyces nigrium, Thermococcus purpureus, Thermomyces purpureus, Thermomyces, Thermococcus, Thermocoria, Thermococcus, Thermocoria, Thermococcus, Thermorus, Ther. Particularly preferably, the DNA polymerase having 5' nuclease activity is Taq polymerase.

Alternatively, in step (2), two different enzymes may be used: nucleic acid polymerases and enzymes having 5' nuclease activity. In such embodiments, the nucleic acid polymerase is used to catalyze the extension of the upstream oligonucleotide sequence using the target nucleic acid sequence as a template, and the enzyme having 5' nuclease activity binds to the extension product of the upstream oligonucleotide sequence and catalyzes the cleavage of the mediator probe.

In certain preferred embodiments, in steps (1) and/or (2), the sample is also contacted with a downstream oligonucleotide sequence (or downstream primer) specific for the target nucleic acid sequence. In certain embodiments, the use of a nucleic acid polymerase and a downstream oligonucleotide sequence (or downstream primer) is particularly advantageous. In particular, the nucleic acid polymerase can generate additional target nucleic acid sequences using the target nucleic acid sequence as a template and the upstream and downstream oligonucleotide sequences as primers, thereby increasing the sensitivity of the methods of the invention.

Thus, in certain preferred embodiments, in step (1), in addition to the upstream oligonucleotide sequence and mediator probe defined above, a downstream oligonucleotide sequence is provided for each target nucleic acid sequence to be detected; wherein the downstream oligonucleotide sequence comprises a sequence complementary to the target nucleic acid sequence; and, when hybridized to the target nucleic acid sequence, the downstream oligonucleotide sequence is located downstream of the target-specific sequence;

the sample is then contacted with the provided upstream oligonucleotide sequences, mediator probes, and downstream oligonucleotide sequences under conditions that allow nucleic acid hybridization.

In such embodiments, the upstream and downstream oligonucleotide sequences serve as upstream and downstream primers, respectively, for amplification of the target nucleic acid sequence. Thus, it is readily understood that the upstream and downstream oligonucleotide sequences are targeted to different ones of the two complementary strands, respectively. Thus, when the target nucleic acid sequence is a double-stranded molecule, the upstream and downstream oligonucleotide sequences are complementary to different strands (sense and antisense strands) of the target nucleic acid sequence, respectively; when the target nucleic acid sequence is a single-stranded molecule, the upstream oligonucleotide sequence and the downstream oligonucleotide sequence are respectively complementary with the target nucleic acid sequence and a complementary sequence thereof, so that the amplification of the target nucleic acid sequence can be realized. However, in the present application, for the sake of simplicity, when describing the relationship of the upstream oligonucleotide sequence/downstream oligonucleotide sequence to the target nucleic acid sequence, they are collectively referred to as "complementary to the target nucleic acid sequence", and the sense strand and the antisense strand of the target nucleic acid sequence are not distinguished in detail, and the target nucleic acid sequence and its complementary sequence are not distinguished in detail. However, the complementary and positional relationship of the upstream/downstream oligonucleotide sequences to the target nucleic acid sequence can be properly understood by those skilled in the art.

For example, when the methods of the invention are used to detect first and second target nucleic acid sequences specific for first and second bacterial serotypes, respectively, first and second downstream oligonucleotide sequences may be provided that comprise sequences complementary to the first and second target nucleic acid sequences, respectively. Similarly, a third downstream oligonucleotide sequence can be provided for a third target nucleic acid sequence specific for a third bacterial serotype that comprises a sequence complementary to the third target nucleic acid sequence. A fourth downstream oligonucleotide sequence comprising a sequence complementary to a fourth target nucleic acid sequence may also be provided for the fourth target nucleic acid sequence specific for a fourth bacterial serotype.

Further, in certain preferred embodiments, in step (2), the product of step (1) is contacted with a nucleic acid polymerase (particularly preferably, a nucleic acid polymerase having 5' nuclease activity). In a further preferred embodiment, the product of step (1) is contacted with a nucleic acid polymerase having 5' nuclease activity under conditions that allow for nucleic acid amplification. In such embodiments, the nucleic acid polymerase will amplify the target nucleic acid sequence using the upstream and downstream oligonucleotides as primers. And, during amplification of the target nucleic acid, the nucleic acid polymerase induces cleavage of the mediator probe hybridized to the target nucleic acid sequence by its own 5' nuclease activity, thereby releasing the mediator fragment comprising the mediator sequence or a portion thereof. The methods of the invention can be carried out using a variety of nucleic acid polymerases having 5' nuclease activity, particularly those described above. In the present application, it is particularly preferred that the nucleic acid polymerase used is a template-dependent nucleic acid polymerase (e.g., a template-dependent DNA polymerase).

In certain embodiments of the invention, the downstream oligonucleotide sequence may comprise or consist of naturally occurring nucleotides (e.g., deoxyribonucleotides or ribonucleotides), modified nucleotides, non-natural nucleotides, or any combination thereof.

In the method of the present invention, the downstream oligonucleotide sequence is not limited by its length as long as it can specifically hybridize to the target nucleic acid sequence. For example, the length of the downstream oligonucleotide sequence may be 15-150nt, such as 15-20nt, 20-30nt, 30-40nt, 40-50nt, 50-60nt, 60-70nt, 70-80nt, 80-90nt, 90-100nt, 100-110nt, 110-120nt, 120-130nt, 130-140nt, 140-150 nt.

In certain preferred embodiments, the target nucleic acid sequence is amplified in a symmetric amplification manner. In such embodiments, amplification is performed using equal amounts of upstream and downstream oligonucleotide sequences for a target nucleic acid sequence. In certain preferred embodiments, the target nucleic acid sequence is amplified in an asymmetric amplification manner. In such embodiments, amplification is performed using unequal amounts of upstream and downstream oligonucleotide sequences for a particular target nucleic acid sequence. In certain embodiments, the upstream oligonucleotide sequence is in excess (e.g., at least 1-fold, at least 2-fold, at least 5-fold, at least 8-fold, at least 10-fold, e.g., 1-10-fold excess) relative to the downstream oligonucleotide sequence. In certain embodiments, the downstream oligonucleotide sequence is in excess (e.g., at least 1-fold, at least 2-fold, at least 5-fold, at least 8-fold, at least 10-fold, e.g., 1-10-fold excess) relative to the upstream oligonucleotide sequence.

In certain preferred embodiments, the target nucleic acid sequence is amplified in a three-step process. In such embodiments, each round of nucleic acid amplification requires three steps: the nucleic acid denaturation is performed at a first temperature, the nucleic acid annealing is performed at a second temperature, and the nucleic acid extension is performed at a third temperature. In certain preferred embodiments, the target nucleic acid sequence is amplified in a two-step process. In such embodiments, each round of nucleic acid amplification requires two steps: the nucleic acid denaturation is performed at a first temperature, and the nucleic acid annealing and extension is performed at a second temperature. The temperature suitable for performing nucleic acid denaturation, nucleic acid annealing, and nucleic acid extension can be readily determined by one skilled in the art by conventional methods (see, e.g., Joseph Sambrook, et al, Molecular Cloning, a Laboratory Manual, Cold Spring Harbor Laboratory press, Cold Spring Harbor, n.y. (2001)).

In the method of the present invention, the mediator probes used generally correspond one-to-one to the target nucleic acid sequence. In other words, a unique mediator probe is provided for each target nucleic acid sequence to be detected. However, it is readily understood that there need not be a one-to-one correspondence between the upstream oligonucleotide sequences, the downstream oligonucleotide sequences, and the target nucleic acid sequences. For example, in some cases, the sample tested is a DNA library, and one or both ends of all fragments in the library comprise the same linker. In this case, the same upstream oligonucleotide sequence may be used for extension, or the same upstream oligonucleotide sequence and/or downstream oligonucleotide sequence may be used for amplification and thereby inducing cleavage of the mediator probe. Thus, in the methods of the invention, the same or different upstream oligonucleotide sequences may be used for different target nucleic acid sequences; and/or, the same or different downstream oligonucleotide sequences may be used. For example, the first, second, third and fourth upstream oligonucleotide sequences may be the same or different. The first, second, third and fourth downstream oligonucleotide sequences may also be the same or different.

Furthermore, when a Nucleic acid polymerase having 5' nuclease activity is used in step (2), a HANDS strategy can also be employed to increase the efficiency of Nucleic acid amplification (see, for example, Nucleic Acids Research,1997,25(16): 3235; 3241). For example, in certain preferred embodiments, an identical oligonucleotide sequence can be introduced at the 5' end of all upstream and downstream oligonucleotide sequences, and amplification can be performed using universal primers complementary to the identical oligonucleotide sequence (preferably in an amount generally much greater than the upstream and downstream oligonucleotide sequences).

Thus, in certain preferred embodiments, in step (1), all of the upstream oligonucleotide sequences (e.g., first, second, third and fourth upstream oligonucleotide sequences) and downstream oligonucleotide sequences (e.g., first, second, third and fourth downstream oligonucleotide sequences) provided have an identical oligonucleotide sequence at the 5' end, and a universal primer is also provided, the universal primer having a sequence complementary to the identical oligonucleotide sequence; the sample is then contacted with the provided upstream oligonucleotide sequences, mediator probes, downstream oligonucleotide sequences and universal primers under conditions that allow nucleic acid hybridization. In certain preferred embodiments, the identical oligonucleotide sequences are 8-50nt in length, e.g., 8-15nt, 15-20nt, 20-30nt, 30-40nt, or 40-50 nt. Accordingly, the universal primer may be 8-50nt in length, such as 8-15nt, 15-20nt, 20-30nt, 30-40nt, or 40-50 nt. Subsequently, in certain preferred embodiments, in step (2), the product of step (1) is contacted with a nucleic acid polymerase (particularly preferably, a nucleic acid polymerase having 5' nuclease activity). In a further preferred embodiment, the product of step (1) is contacted with a nucleic acid polymerase having 5' nuclease activity under conditions that allow for nucleic acid amplification. In such embodiments, the nucleic acid polymerase will perform a preliminary amplification of the target nucleic acid sequence using the upstream and downstream oligonucleotides as primers to obtain a preliminary amplified product; subsequently, the preliminarily amplified product is subjected to re-amplification using the universal primer. And, throughout the amplification process, the nucleic acid polymerase cleaves the mediator probe hybridized to the target nucleic acid sequence or the product of the preliminary amplification by its own 5' nuclease activity, thereby releasing the mediator fragment comprising the mediator sequence or a portion thereof.

In certain embodiments of the invention, the universal primer may comprise or consist of naturally occurring nucleotides (e.g., deoxyribonucleotides or ribonucleotides), modified nucleotides, non-natural nucleotides, or any combination thereof.

In the method of the present invention, the universal primer is not limited in its length as long as it can specifically hybridize to the same oligonucleotide sequences contained in the upstream and downstream oligonucleotide sequences. For example, the universal primer can be 8-50nt in length, such as 8-15nt, 15-20nt, 20-30nt, 30-40nt, or 40-50 nt.

With respect to steps (3) and (4)

In step (2), the mediator probe hybridized to the target nucleic acid sequence is cleaved by an enzyme having 5' nuclease activity, releasing a mediator fragment containing the mediator sequence or a portion thereof, which is then hybridized to the detection probe in step (3). In the present application, the detection probe comprises, in the 3 'to 5' direction, a capture sequence complementary to each of the mediator sequences or portions thereof, and a template sequence. Thus, in step (4), the detection probe is used as a template for extension of the mediator fragment under the action of the nucleic acid polymerase; and the vector fragment serves as a primer for initiating the extension reaction; and after the extension reaction is finished, the extension product of the mediator fragment is hybridized with the detection probe to form a nucleic acid duplex.

In the methods of the invention, the detection probe comprises a plurality of capture sequences that are complementary to the plurality of mediator sequences or portions thereof (e.g., a first capture sequence that is complementary to a first mediator sequence or portion thereof, a second capture sequence that is complementary to a second mediator sequence or portion thereof, a third capture sequence that is complementary to a third mediator sequence or portion thereof, and/or a fourth capture sequence that is complementary to a fourth mediator sequence or portion thereof). It will be readily appreciated that the individual capture sequences may be arranged in any order. For example, the first capture sequence may be located upstream (5 'end) or downstream (3' end) of the second capture sequence. For example, the detection probe may comprise, in order from 3 'to 5', a first capture sequence and a second capture sequence; alternatively, the second capture sequence and the first capture sequence. Similarly, the detection probes can comprise additional capture sequences (e.g., first, second, third, fourth capture sequences) in any order.

Furthermore, the individual capture sequences may be arranged in any manner. For example, the capture sequences can be arranged in an adjacent manner or in a spaced-apart manner with a linker sequence. For example, the first capture sequence may be arranged adjacent to the second capture sequence; alternatively, the two may be separated by a linker sequence (also referred to herein simply as a "linker"); alternatively, there may be an overlap between the two. Similarly, the detection probes can comprise additional capture sequences (e.g., first, second, third, fourth capture sequences) in any arrangement.

In some cases, it is particularly advantageous to arrange the individual capture sequences in an overlapping manner. In such embodiments, the plurality of media subsequences can be designed such that different media subsequences comprise overlapping sequences. For example, the first and second intermediate subsequences may be designed such that the 3 'end portion of the first intermediate subsequence has the same sequence as the 5' end portion of the second intermediate subsequence. Accordingly, in the detection probe, the 5 'end portion of the first capture sequence complementary to the first mediator sequence has the same sequence as the 3' end portion of the second capture sequence complementary to the second mediator sequence. Thus, the detection probe may comprise the first capture sequence and the second capture sequence in a 3 'to 5' orientation, and both may be arranged in an overlapping manner. In this case, the overlapping sequence is the same sequence or a portion thereof that is common to the first and second capture sequences. By arranging the capture sequences in an overlapping manner, the detection probe can be made to comprise more capture sequences within a predetermined length, thereby allowing hybridization to more mediator subsections. In other words, by arranging the capture sequences in an overlapping manner, a single detection probe may be used in combination with more mediator sub-probes.

As described above, in the methods of the invention, a single detection probe is used in combination with at least 2 (e.g., 3, 4, 5,6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more) mediator sub-probes. Thus, in certain preferred embodiments, a single detection probe is used in excess (e.g., at least 1-fold, at least 2-fold, at least 5-fold, at least 10-fold, at least 20-fold excess) relative to a single mediator probe. Such embodiments are advantageous in certain circumstances because the entire reaction system contains enough detection probes to hybridize with the released mediator fragments, mediate extension of the mediator fragments, and form duplexes.

As described above, a media sub-fragment may contain the entire media sub-sequence or a portion thereof. When the mediator fragment comprises the entire mediator subsequence, the detection probe preferably comprises a sequence complementary to the mediator subsequence. When the mediator sub-fragment comprises a portion (5 '-end portion) of the mediator sequence, the detection probe may preferably comprise a sequence complementary to the portion (5' -end portion) of the mediator sequence, or a sequence complementary to the entire mediator sequence. In certain preferred embodiments, the detection probe comprises a sequence complementary to the mediator sequence. Such detection probes are particularly advantageous in certain cases because they are capable of hybridizing to both vector subsegments containing the entire vector subsequence, and vector subsegments containing portions (5' -end portions) of the vector subsequence. However, it will be appreciated that the detection probe may also comprise a sequence that is complementary to only a portion (e.g., the 3' -end portion) of the mediator segment, so long as the detection probe is capable of stably hybridizing to the mediator segment and initiating the extension reaction.

Furthermore, the detection probe may comprise additional sequences at the 3' end (i.e., downstream of the capture sequence) in addition to the capture sequence and the template sequence. The additional sequences typically comprise sequences that are not complementary to the mediator sub-fragments and do not participate in hybridization with the mediator sub-fragments.

According to the invention, the template sequence in the detection probe may comprise any sequence and is located upstream (5' to) the respective capture sequence, and thus may be used as a template for extension of the media fragment. In certain preferred embodiments, the template sequence comprises a sequence that is not complementary to the mediator probe (mediator sequence and target-specific sequence). Such a template sequence is particularly advantageous in certain cases because it can improve the hybridization specificity of the mediator fragment to the detection probe, avoiding hybridization of the mediator fragment to undesired locations and thus avoiding the generation of undesired duplexes.

In certain embodiments of the invention, the detection probe may comprise or consist of naturally occurring nucleotides (e.g., deoxyribonucleotides or ribonucleotides), modified nucleotides, non-natural nucleotides (e.g., Peptide Nucleic Acids (PNAs) or locked nucleic acids), or any combination thereof.

In the method of the present invention, the detection probe is not limited by its length. For example, the length of the detection probe can be 15-1000nt, such as 15-20nt, 20-30nt, 30-40nt, 40-50nt, 50-60nt, 60-70nt, 70-80nt, 80-90nt, 90-100nt, 100-200nt, 200-300nt, 300-400nt, 400-500nt, 500-600nt, 600-700nt, 700-800nt, 800-900nt, 900-1000 nt. The capture sequence in the detection probe may be of any length so long as it is capable of specifically hybridizing to the vector subsegment. For example, the length of the capture sequence in the detection probe can be 10-500nt, such as 10-20nt, 20-30nt, 30-40nt, 40-50nt, 50-60nt, 60-70nt, 70-80nt, 80-90nt, 90-100nt, 100-150nt, 150-200nt, 200-250nt, 250-300nt, 300-350nt, 350-400nt, 400-450nt, 450-500 nt. The template sequence in the detection probe may be of any length as long as it can serve as a template for extension of the vector fragment. For example, the length of the template sequence in the detection probe may be 1-900nt, such as 1-5nt, 5-10nt, 10-20nt, 20-30nt, 30-40nt, 40-50nt, 50-60nt, 60-70nt, 70-80nt, 80-90nt, 90-100nt, 100-200nt, 200-300nt, 300-400nt, 400-500nt, 500-600nt, 600-700nt, 700-800nt, 800-900 nt. In certain preferred embodiments, the length of the capture sequence in the detection probe is 10-200nt (e.g., 10-190nt, 10-180nt, 10-150nt, 10-140nt, 10-130nt, 10-120nt, 10-100nt, 10-90nt, 10-80nt, 10-50nt, 10-40nt, 10-30nt, 10-20nt), and the length of the template sequence is 5-200nt (e.g., 10-190nt, 10-180nt, 10-150nt, 10-140nt, 10-130nt, 10-120nt, 10-100nt, 10-90nt, 10-80nt, 10-50nt, 10-40nt, 10-30nt, 10-20 nt).

In certain preferred embodiments, the detection probe has a 3' -OH terminus. In certain preferred embodiments, the 3' -end of the detection probe is blocked to inhibit extension thereof. The 3' -end of a nucleic acid (e.g., a detection probe) can be blocked by various methods. For example, the 3 '-end of the detection probe can be blocked by modifying the 3' -OH of the last nucleotide of the detection probe. In certain embodiments, the 3 '-end of the detection probe can be blocked by adding a chemical moiety (e.g., biotin or alkyl) to the 3' -OH of the last nucleotide of the detection probe. In certain embodiments, the 3 '-end of the detection probe can be blocked by removing the 3' -OH of the last nucleotide of the detection probe, or replacing the last nucleotide with a dideoxynucleotide.

In the method of the invention, the mediator fragment is hybridized to the detection probe and thereby initiates an extension reaction of the nucleic acid polymerase. Although the uncleaved mediator probe is also capable of hybridizing to the detection probe via the mediator subsequence, the mediator probe further comprises a target-specific sequence that is downstream of the mediator subsequence and that does not hybridize to the detection probe (i.e., is in a free state), such that the nucleic acid polymerase cannot extend the mediator probe hybridized to the detection probe.

As described above, the detection probe is labeled with a reporter group and a quencher group, wherein the reporter group is capable of emitting a signal and the quencher group is capable of absorbing or quenching the signal emitted by the reporter group; and wherein the detection probe emits a signal when hybridized to its complement that is different from the signal when not hybridized to its complement.

In certain preferred embodiments, the detection probe is a self-quenching probe. In such embodiments, the quencher is positioned to absorb or quench the signal from the reporter (e.g., the quencher is positioned adjacent to the reporter) when the detection probe is not hybridized to the other sequence, thereby absorbing or quenching the signal from the reporter. In this case, the detection probe does not emit a signal. Further, when the detection probe hybridizes to its complement, the quencher is located at a position that is unable to absorb or quench the signal from the reporter (e.g., the quencher is located at a position remote from the reporter), and thus unable to absorb or quench the signal from the reporter. In this case, the detection probe emits a signal.

The design of such self-quenching detection probes is within the ability of those skilled in the art. For example, the detection probe may be labeled with a reporter group at the 5 'end and a quencher group at the 3' end, or the detection probe may be labeled with a reporter group at the 3 'end and a quencher group at the 5' end. Whereby, when the detection probe is present alone, the reporter and the quencher are in proximity to each other and interact such that a signal emitted by the reporter is absorbed by the quencher, thereby causing no signal to be emitted by the detection probe; and when the detection probe hybridizes to its complementary sequence, the reporter and the quencher are separated from each other such that a signal from the reporter is not absorbed by the quencher, thereby causing the detection probe to emit a signal.

However, it will be appreciated that the reporter and quencher need not be labeled at the terminus of the detection probe. The reporter and/or quencher may also be labeled within the detection probe, so long as the detection probe emits a signal upon hybridization to its complementary sequence that is different from the signal emitted without hybridization to its complementary sequence. For example, the reporter can be labeled upstream (or downstream) of the detection probe and the quencher can be labeled downstream (or upstream) of the detection probe at a sufficient distance (e.g., 10-20nt, 20-30nt, 30-40nt, 40-50nt, 50-60nt, 60-70nt, 70-80nt, or longer). Whereby, when the detection probe is present alone, the reporter and the quencher are in proximity to each other and interact due to free coil of the probe molecule or formation of a secondary structure (e.g., hairpin structure) of the probe such that the signal emitted by the reporter is absorbed by the quencher, thereby rendering the detection probe non-emitting a signal; and, when the detection probe hybridizes to its complement, the reporter and the quencher are separated from each other by a sufficient distance such that the signal from the reporter is not absorbed by the quencher, thereby causing the detection probe to emit a signal. In certain preferred embodiments, the reporter and quencher are separated by a distance of 10-80nt or more, e.g., 10-20nt, 20-30nt, 30-40nt, 40-50nt, 50-60nt, 60-70nt, 70-80 nt. In certain preferred embodiments, the reporter and quencher are separated by no more than 80nt, no more than 70nt, no more than 60nt, no more than 50nt, no more than 40nt, no more than 30nt, or no more than 20 nt. In certain preferred embodiments, the reporter and quencher are separated by at least 5nt, at least 10nt, at least 15nt, or at least 20 nt.

Thus, the reporter and quencher can be labeled at any suitable position on the detection probe, so long as the detection probe emits a signal upon hybridization to its complementary sequence that is different from the signal emitted without hybridization to its complementary sequence. However, in certain preferred embodiments, at least one of the reporter and quencher is at the terminus (e.g., the 5 'or 3' terminus) of the detection probe. In certain preferred embodiments, one of the reporter and the quencher is located at the 5 'end of the detection probe or 1-10nt from the 5' end, and the reporter and the quencher are suitably spaced apart such that the quencher is capable of absorbing or quenching the signal of the reporter prior to hybridization of the detection probe to its complementary sequence. In certain preferred embodiments, one of the reporter and the quencher is located at the 3 'end of the detection probe or 1-10nt from the 3' end, and the reporter and the quencher are suitably spaced apart such that the quencher is capable of absorbing or quenching the signal of the reporter prior to hybridization of the detection probe to its complementary sequence. In certain preferred embodiments, the reporter and quencher can be separated by a distance as defined above (e.g., a distance of 10-80nt or more). In certain preferred embodiments, one of the reporter and quencher is at the 5 'end of the detection probe and the other is at the 3' end.

In the methods of the invention, the reporter and quencher can be any suitable group or molecule known in the art, specific examples of which include, but are not limited to, Cy2^TM(506),YO-PRO^TM-l(509),YOYO^TM-l(509),Calcein(517),FITC(518),FluorX^TM(519),Alexa^TM(520),Rhodamine 110(520),Oregon Green^TM500(522),Oregon Green^TM488(524),RiboGreen^TM(525),Rhodamine Green^TM(527),Rhodamine123(529),Magnesium Green^TM(531),Calcium Green^TM(533),TO-PRO^TM-l(533),TOTOl(533),JOE(548),BODIPY530/550(550),Dil(565),BODIPY TMR(568),BODIPY558/568(568),BODIPY564/570(570),Cy3^TM(570),Alexa^TM546(570),TRITC(572),MagnesiumOrange^TM(575),Phycoerythrin R&B(575),Rhodamine Phalloidin(575),CalciumOrange^TM(576),PyroninY(580),Rhodamine B(580),TAMRA(582),Rhodamine Red^TM(590),Cy3.5^TM(596),ROX(608),Calcium Crimson^TM(615),Alexa^TM594(615),Texas Red(615),Nile Red(628),YO-PRO^TM-3(631),YOYO^TM-3(631),R-phycocyanin(642),C-Phycocyanin(648),TO-PRO^TM-3(660),T0T03(660),DiD DilC(5)(665),Cy5^TM(670) Thiadiacarbyanine (671), Cy5.5(694), HEX (556), TET (536), Biosearch Blue (447), CALFluor Gold540(544), CAL Fluor Orange 560(559), CAL Fluor Red 590(591), CAL Fluor Red 610(610), CAL Fluor Red 635(637), FAM (520), Fluorescein (520), Fluorescein-C3(520), Pulsar 650(566), Quasar 570(667), Quasar670(705), and Quasar 705 (610). The numbers in parentheses indicate the maximum emission wavelength in nm.

In addition, various suitable pairs of reporter and quencher groups are known in the art, see, e.g., Pesce et al, editors, Fluorescence Spectroscopy (Marcel Dekker, New York, 1971); white et al, Fluorescence Analysis, A Practical Approach (Marcel Dekker, New York, 1970); berlman, Handbook of Fluorescence Spectra of Aromatic Molecules,2nd Edition (Academic Press, New York, 1971); griffiths, Color AND Consistition of OiganicMolles (Academic Press, New York, 1976); bishop, editor, Indicators (PeigilonPress, Oxford, 1972); haughland, Handbook of Fluorescent Probes and research Chemicals (Molecular Probes, Eugene, 1992); pringsheim, Fluoroscience and Phosphorescence (Interscience Publishers, New York, 1949); haughland, R.P., handbook of Fluorescent Probes and Research Chemicals,6th Edition (Molecular Probes, Eugene, Oreg., 1996); U.S. Pat. nos. 3,996,345 and 4,351,760.

In certain preferred embodiments, the reporter is a fluorophore. In such embodiments, the signal emitted by the reporter is fluorescence, and the quencher is a molecule or group capable of absorbing/quenching the fluorescence (e.g., another fluorescent molecule capable of absorbing the fluorescence, or a quencher capable of quenching the fluorescence). In certain preferred embodiments, the fluorescent group includes, but is not limited to, various fluorescent molecules, such as ALEX-350, FAM, VIC, TET, CAL

Gold540, JOE, HEX, CAL Fluor Orange 560, TAMRA, CAL Fluor Red 590, ROX, CAL Fluor Red 610, TEXAS RED, CAL Fluor Red 635, Quasar670, CY3, CY5, CY5.5, Quasar 705 and the like. In certain preferred embodiments, the quenching group includes, but is not limited to, various quenchers, such as DABCYL, BHQ (e.g., BHQ-1 or BHQ-2), ECLIPSE, and/or TAMRA, and the like.

In the methods of the invention, the detection probe may also be modified, for example, to be resistant to nuclease activity (e.g., 5' nuclease activity, e.g., 5' to 3' exonuclease activity). For example, modifications that resist nuclease activity, such as phosphorothioate linkages, alkylphosphotriester linkages, arylphosphotriester linkages, alkylphosphonate linkages, arylphosphonate linkages, hydrogenphosphate linkages, alkylaminophosphate linkages, arylaminophosphate linkages, 2' -O-aminopropyl modifications, 2' -O-alkyl modifications, 2' -O-allyl modifications, 2' -O-butyl modifications, and 1- (4' -thio-PD-ribofuranosyl) modifications may be introduced into the backbone of the detection probe.

In the methods of the invention, the detection probe may be linear or may have a hairpin structure. In certain preferred embodiments, the detection probe is linear. In certain preferred embodiments, the detection probe has a hairpin structure. Hairpin structures may be natural or artificially introduced. In addition, detection probes having hairpin structures can be constructed using methods conventional in the art. For example, the detection probe can form a hairpin structure by adding complementary 2 oligonucleotide sequences at the 2 termini (5 'and 3' ends) of the detection probe. In such embodiments, the complementary 2 oligonucleotide sequences constitute the arms (stems) of the hairpin structure. The arms of the hairpin structure may have any desired length, for example the length of the arms may be 2-15nt, for example 3-7nt, 4-9nt, 5-10nt, 6-12 nt.

Furthermore, in the method of the present invention, "hybridization", "nucleic acid hybridization" and "conditions allowing nucleic acid hybridization" in step (3) may be as defined above.

Performing step (4) using the product of step (3) and a nucleic acid polymerase. In step (4), the nucleic acid polymerase will extend the fragment of the mediator hybridised to the detection probe using the detection probe as a template under conditions which allow the nucleic acid polymerase to perform an extension reaction and thereby form a duplex.

As described in detail above, each mediator probe comprises a unique mediator sequence and, under the action of an enzyme having 5' nuclease activity, releases a mediator fragment comprising the unique mediator sequence or a portion thereof. Each mediator fragment is then hybridized to a different location of the detection probe (i.e., a capture sequence complementary to the corresponding mediator subsequence, or portion thereof), extended by a nucleic acid polymerase, and forms a duplex with the detection probe. Thus, for each mediator probe, when its corresponding target sequence is present, a unique duplex will be generated in step (4) comprising the detection probe (as one strand) and the extension product of the mediator fragment corresponding to that mediator probe (as the other strand). Thus, each of the duplexes produced in step (4) has a structure (sequence) different from each other, and thus has a T different from each other_mAnd show melting peaks different from each other in melting curve analysis.

In certain preferred embodiments, the nucleic acid polymerase used in step (4) is a template-dependent nucleic acid polymerase (e.g., a DNA polymerase, particularly a thermostable DNA polymerase). In certain preferred embodiments, the nucleic acid polymerase is a thermostable DNA polymerase obtainable from various bacterial species, for example, Thermus aquaticus (Taq), Thermus thermophilus (Tth), Thermus filiformis, Thermus flavus, Thermococcuslitheralis, Thermus antalidanii, Thermus caldophyllolus, Thermus californica, Thermus canorubenus, Thermus scomoductus, Thermus silvareum, Thermus lignerutera, Thermus lacteus, Thermus osihimai, Thermus ruber, Thermus canubebens, Thermus scodottus, Thermus thermophilus, Thermotaria maritima, Thermomyces neocaris, Thermococcus purpurea, Thermomyces neocaris, Thermococcus neospora, Thermocapina neospora, Thermocapiaria, Thermococicola, Thermoccharosis, Thermococicola, Thermoctoria, Thermocapium, Thermoctoria, Thermocapium, Thermoccharosis, Thermocapium purpura, Thermoccharosis, Thermococicola, Thermoccharosis. Particularly preferably, the template-dependent nucleic acid polymerase is Taq polymerase.

In certain preferred embodiments, the enzyme having 5 'nuclease activity used in step (2) is a nucleic acid polymerase having 5' nuclease activity and is the same as the nucleic acid polymerase used in step (4). In certain preferred embodiments, the enzyme having 5' nuclease activity used in step (2) is different from the nucleic acid polymerase used in step (4).

For example, in certain embodiments, in step (2), a first nucleic acid polymerase is used to catalyze extension of the upstream oligonucleotide sequence and an enzyme with 5' nuclease activity is used to catalyze cleavage of the mediator probe, followed by a second nucleic acid polymerase in step (4) to catalyze extension of the mediator fragment. In certain embodiments, in step (2), a first nucleic acid polymerase having 5' nuclease activity is used to catalyze the extension of the upstream oligonucleotide sequence and cleavage of the mediator probe, followed by a second nucleic acid polymerase used to catalyze the extension of the mediator fragment in step (4). However, it is particularly preferred to use the same enzyme in steps (2) and (4). For example, a template-dependent nucleic acid polymerase having 5' nuclease activity (e.g., a DNA polymerase, particularly a thermostable DNA polymerase) may be used to catalyze the extension of the upstream oligonucleotide sequence and cleavage of the mediator probe in step (2), and to catalyze the extension of the mediator fragment in step (4).

In the method of the present invention, one or more of steps (1) to (4) may be repeatedly performed as necessary. In certain preferred embodiments, steps (1) - (2) are repeated one or more times, and prior to each repetition, a step of nucleic acid denaturation is performed. It will be readily appreciated that the repetition of steps (1) - (2) may result in more media sub-segments for subsequent steps (i.e., steps (3) - (5)). Thus, in certain preferred embodiments, the process of the invention is carried out by the following scheme: repeating steps (1) - (2) one or more times, and prior to each repetition, performing a nucleic acid denaturation step; followed by steps (3) - (5).

In certain preferred embodiments, steps (1) - (4) are repeated one or more times, and prior to each repetition, a step of nucleic acid denaturation is performed. It will be readily appreciated that repetition of steps (1) - (4) may result in more duplexes of extension products comprising the detection probe and the mediator fragment for use in subsequent steps (i.e., step (5)). Thus, in certain preferred embodiments, the process of the invention is carried out by the following scheme: repeating steps (1) - (4) one or more times, and prior to each repetition, performing a nucleic acid denaturation step; step (5) is then performed.

In certain preferred embodiments, steps (1) - (4) of the method of the invention may be carried out by a protocol comprising the following steps (a) - (f):

(a) providing a detection probe and, for each target nucleic acid sequence to be detected, an upstream oligonucleotide sequence, a mediator probe and a downstream oligonucleotide sequence; and, optionally, providing a universal primer; wherein the detection probe, mediator probe, upstream oligonucleotide sequence, downstream oligonucleotide sequence and universal primer are as defined above;

(b) mixing the sample to be tested with the provided detection probe, upstream oligonucleotide sequence, mediator probe and downstream oligonucleotide sequence, and a template-dependent nucleic acid polymerase having 5' nuclease activity (e.g., a DNA polymerase, particularly a thermostable DNA polymerase); and optionally, adding a universal primer;

(c) incubating the product of the previous step under conditions that allow denaturation of the nucleic acids;

(d) incubating the product of the previous step under conditions that allow annealing or hybridization of the nucleic acid;

(e) incubating the product of the previous step under conditions that allow for extension of the nucleic acid; and

(f) optionally, repeating steps (c) - (e) one or more times.

In such embodiments, in step (c), all nucleic acid molecules in the sample will dissociate into a single stranded state; subsequently, in step (d), complementary nucleic acid molecules (e.g., extension products of the upstream oligonucleotide sequence and the target nucleic acid sequence or the downstream oligonucleotide sequence, extension products of the downstream oligonucleotide sequence and the target nucleic acid sequence or the upstream oligonucleotide sequence, mediator probes and the target nucleic acid sequence or amplification products thereof, mediator probes or mediator fragments resulting from cleavage of the mediator probes and detection probes, universal primers and the upstream/downstream oligonucleotide sequence or the extension products of the upstream/downstream oligonucleotide sequence) will anneal or hybridize together to form a duplex; subsequently, in step (e), the template-dependent nucleic acid polymerase having 5 'nuclease activity will extend the upstream/downstream oligonucleotide sequences hybridized to the target nucleic acid sequence, cleave the free 5' end of the mediator probe hybridized to the target nucleic acid sequence, extend the mediator fragment hybridized to the detection probe, and extend the universal primer hybridized to the extension product of the upstream/downstream oligonucleotide sequences. Thus, by cycling through steps (c) - (e), amplification of the target nucleic acid sequence, cleavage of the mediator probe, and formation of a duplex containing the extension product of the detection probe and the mediator fragment can be achieved, thereby completing steps (1) - (4) of the method of the present invention.

It will be readily appreciated that the nucleic acid polymerase does not extend the mediator probe hybridized to the detection probe, since the target-specific sequence at the 3' end of the mediator probe is not hybridized to the detection probe, and is free. Furthermore, it is preferable that the 3' end of the mediator probe is blocked, so that undesired extension of the mediator probe, for example, extension of the mediator probe hybridized to a target nucleic acid sequence or a detection probe, can be prevented.

The incubation time and temperature of step (c) can be routinely determined by one skilled in the art. In certain preferred embodiments, in step (c), the product of step (b) is incubated at a temperature of 80-105 ℃ (e.g., 80-85 ℃, 85-90 ℃, 90-95 ℃, 91 ℃, 92 ℃, 93 ℃, 94 ℃, 95 ℃, 96 ℃,97 ℃, 98 ℃,99 ℃, 100 ℃, 101 ℃, 102 ℃, 103 ℃, 104 ℃, or 105 ℃) to thereby denature the nucleic acid. In certain preferred embodiments, in step (c), the product of step (b) is incubated for 10s to 5min, e.g., 10 to 20s, 20 to 40s, 40 to 60s, 1 to 2min, or 2 to 5 min.

The incubation time and temperature of step (d) can be routinely determined by one skilled in the art. In certain preferred embodiments, in step (d), the product of step (c) is incubated at a temperature of 35-70 ℃ (e.g., 35-40 ℃, 40-45 ℃, 45-50 ℃, 50-55 ℃, 55-60 ℃, 60-65 ℃, or 65-70 ℃) to allow annealing or hybridization of the nucleic acids. In certain preferred embodiments, in step (d), the product of step (c) is incubated for 10s to 5min, e.g., 10 to 20s, 20 to 40s, 40 to 60s, 1 to 2min, or 2 to 5 min.

The incubation time and temperature of step (e) can be routinely determined by one skilled in the art. In certain preferred embodiments, in step (e), the product of step (d) is incubated at a temperature of 35-85 ℃ (e.g., 35-40 ℃, 40-45 ℃, 45-50 ℃, 50-55 ℃, 55-60 ℃, 60-65 ℃, 65-70 ℃, 70-75 ℃, 75-80 ℃, 80-85 ℃) to allow nucleic acid extension. In certain preferred embodiments, in step (e), the product of step (d) is incubated for 10s to 30min, e.g., 10 to 20s, 20 to 40s, 40 to 60s, 1 to 2min, 2 to 5min, 5 to 10min, 10 to 20min or 20 to 30 min.

In certain embodiments, steps (d) and (e) may be performed at different temperatures, i.e., annealing and extension of the nucleic acid is performed at different temperatures. In certain embodiments, steps (d) and (e) may be performed at the same temperature, i.e., annealing and extension of the nucleic acid is performed at the same temperature. In this case, steps (d) and (e) may be combined into one step.

In the method of the invention, steps (c) - (e) may be repeated at least once, such as at least 2 times, at least 5 times, at least 10 times, at least 20 times, at least 30 times, at least 40 times, or at least 50 times. In some cases, multiple repetitions of steps (c) - (e) are advantageous because they enable amplification of the target nucleic acid sequence, increasing the sensitivity of detection. However, it will be readily appreciated that the conditions used in steps (c) - (e) for each cycle need not be the same when steps (c) - (e) are repeated one or more times. For example, one condition may be used to perform steps (c) - (e) of the first 5 cycles, followed by another condition to perform steps (c) - (e) of the remaining cycles.

Step (5)

In step (5) of the method according to the invention, the product of step (4) is subjected to a melting curve analysis; and determining whether each of the target nucleic acid sequences is present in the sample based on the results of the melting curve analysis.

As discussed above, melting curve analysis can be performed by using a detection probe labeled with a reporter group and a quencher group.

In certain embodiments, the product of step (4) may be subjected to a gradual temperature increase and the signal emitted by the reporter group on the detection probe monitored in real time to obtain a plot of the signal intensity of the product of step (4) as a function of temperature. For example, the product of step (4) can be gradually warmed from a temperature of 45 ℃ or less (e.g., no more than 45 ℃, no more than 40 ℃, no more than 35 ℃, no more than 30 ℃, no more than 25 ℃) to a temperature of 75 ℃ or more (e.g., at least 75 ℃, at least 80 ℃, at least 85 ℃, at least 90 ℃, at least 95 ℃) and the signal emitted by the reporter group on the detection probe can be monitored in real time to obtain a curve of the intensity of the signal from the reporter group as a function of temperature. The rate of temperature rise may be routinely determined by one skilled in the art. For example, the rate of temperature rise may be: heating at 0.01-1 deg.C per step (such as 0.01-0.05 deg.C, 0.05-0.1 deg.C, 0.1-0.5 deg.C, 0.5-1 deg.C, 0.04-0.4 deg.C, such as 0.01 deg.C, 0.02 deg.C, 0.03 deg.C, 0.04 deg.C, 0.05 deg.C, 0.06 deg.C, 0.07 deg.C, 0.08 deg.C, 0.09 deg.C, 0.1 deg.C, 0.2 deg.C, 0.3 deg.C, 0.4 deg.C, 0.5 deg.C, 0.6 deg.C, 0.7 deg.C, 0.8 deg.C, 0.9 deg.C, or 1.0.0 deg.C), and maintaining at 0.5-15s per step (such as 0.5-1 s; or raising the temperature at 0.01-1 deg.C (e.g., 0.01-0.05 deg.C, 0.05-0.1 deg.C, 0.1-0.5 deg.C, 0.5-1 deg.C, 0.04-0.4 deg.C, e.g., 0.01 deg.C, 0.02 deg.C, 0.03 deg.C, 0.04 deg.C, 0.05 deg.C, 0.06 deg.C, 0.07 deg.C, 0.08 deg.C, 0.09 deg.C, 0.1 deg.C, 0.2 deg.C, 0.3 deg.C, 0.4 deg.C, 0.5 deg.C, 0.6 deg..

In certain embodiments, the product of step (4) may be gradually cooled and the signal from the reporter group on the detection probe monitored in real time to obtain a plot of the signal intensity of the product of step (4) as a function of temperature. For example, the product of step (4) can be gradually cooled from a temperature of 75 ℃ or more (e.g., at least 75 ℃, at least 80 ℃, at least 85 ℃, at least 90 ℃, at least 95 ℃) to a temperature of 45 ℃ or less (e.g., not more than 45 ℃, not more than 40 ℃, not more than 35 ℃, not more than 30 ℃, not more than 25 ℃) and the signal emitted by the reporter on the detection probe can be monitored in real time to obtain a curve of the intensity of the signal from the reporter as a function of temperature. The rate of temperature reduction may be routinely determined by those skilled in the art. For example, the rate of cooling may be: cooling at 0.01-1 deg.C (such as 0.01-0.05 deg.C, 0.05-0.1 deg.C, 0.1-0.5 deg.C, 0.5-1 deg.C, 0.04-0.4 deg.C, such as 0.01 deg.C, 0.02 deg.C, 0.03 deg.C, 0.04 deg.C, 0.05 deg.C, 0.06 deg.C, 0.07 deg.C, 0.08 deg.C, 0.09 deg.C, 0.1 deg.C, 0.2 deg.C, 0.3 deg.C, 0.4 deg.C, 0.5 deg.C, 0.6 deg.C, 0.7 deg.C, 0.8 deg.C, or 1.0 deg.0 deg.C) per step, and maintaining at 0.5-15s (such as 0.5-1s, 1-2s, 2; or reducing the temperature by 0.01-1 deg.C per second (e.g., 0.01-0.05 deg.C, 0.05-0.1 deg.C, 0.1-0.5 deg.C, 0.5-1 deg.C, 0.04-0.4 deg.C, e.g., 0.01 deg.C, 0.02 deg.C, 0.03 deg.C, 0.04 deg.C, 0.05 deg.C, 0.06 deg.C, 0.07 deg.C, 0.08 deg.C, 0.09 deg.C, 0.1 deg.C, 0.2 deg.C, 0.3 deg.C, 0.4 deg.C, 0.5 deg.C, 0.6.

Subsequently, the obtained curve may be derived to obtain a melting curve of the product of step (4). From the melting peak (melting point) in the melting curve, the presence of a media sub-segment corresponding to the melting peak (melting point) can be determined. Subsequently, by the correspondence of the mediator sequence in the mediator fragment to the target nucleic acid sequence, the presence of the target nucleic acid sequence corresponding to the mediator fragment, and thus the bacterial serotype corresponding to the target nucleic acid sequence, can be determined.

For example, when the results of the melting curve analysis show the presence or absence of a melting peak corresponding to a first duplex comprising a detection probe and a first mediator fragment extension product, the presence or absence of a first target nucleic acid sequence/first bacterial serotype in the sample can be determined. Similarly, when the results of the melting curve analysis show the presence or absence of a melting peak corresponding to a second duplex comprising a detection probe and a second mediator fragment extension product, the presence or absence of a second target nucleic acid sequence/second bacterial serotype in the sample can be determined. When the results of the melting curve analysis show the presence or absence of a melting peak corresponding to a third duplex comprising the detection probe and a third mediator segment extension product, it can be determined that a third target nucleic acid sequence/third bacterial serotype is present or absent in the sample. When the results of the melting curve analysis show the presence or absence of a melting peak corresponding to a fourth duplex comprising the detection probe and a fourth mediator segment extension product, it can be determined that a fourth target nucleic acid sequence/fourth bacterial serotype is present or absent in the sample. Thus, the methods of the invention allow for the simultaneous detection (multiplex detection) of at least two (e.g., 2, 3, 4, 5,6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or more) target nucleic acid sequences/bacterial serotypes by using one detection probe and at least two (e.g., 2, 3, 4, 5,6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or more) mediator probes.

Without being bound by theory, the resolution or accuracy of melting curve analysis can reach 0.5 ℃ or higher. In other words, melting curve analysis can distinguish two melting peaks having melting points that differ by only 0.5 ℃ or less (e.g., 0.1 ℃, 0.2 ℃, 0.3 ℃, 0.4 ℃, 0.5 ℃). Thus, in certain embodiments of the methods of the invention, the difference in melting point between any two duplexes (e.g., a first duplex and a second duplex) can be at least 0.5 ℃ (e.g., by designing the sequences of the first mediator subsequence, the second mediator subsequence, and the detection probe) such that the any two duplexes (e.g., the first duplex and the second duplex) can be distinguished and distinguished by melting curve analysis. However, for the purpose of facilitating differentiation and discrimination, a greater difference in melting point of the two duplexes (e.g., the first duplex and the second duplex) may be preferred in some circumstances. Thus, in certain embodiments of the methods of the invention, the difference in melting point between two duplexes (e.g., a first duplex and a second duplex) can be any desired value (e.g., at least 0.5 ℃, at least 1 ℃, at least 2 ℃, at least 3 ℃, at least 4 ℃, at least 5 ℃, at least 8 ℃, at least 10 ℃, at least 15 ℃, or at least 20 ℃) so long as the difference in melting point can be distinguished and distinguished by melt curve analysis.

Simultaneous use of one or more detection probes

In the methods described above, multiple detection of multiple target nucleic acid sequences/bacterial serotypes is achieved using one detection probe. However, it will be readily appreciated that the method of the invention is not limited to the number of detection probes used. The methods of the invention can use one or more detection probes (e.g., at least 1, at least 2, at least 3, at least 4, at least 5, at least 6, or more detection probes). Also, at least two or more kinds (e.g., 2, 3, 4, 5,6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or more kinds of detection probes) of mediator probes can be designed for each detection probe based on the same principle as described above, whereby the method of the present invention can be used for simultaneously detecting the presence of a plurality of target nucleic acid sequences/bacterial serotypes, and the maximum number of target nucleic acid sequences/bacterial serotypes that can be simultaneously detected by the method of the present invention far exceeds the number of detection probes used, and is equal to the sum of the number of mediator probes designed for each detection probe (i.e., the number of all mediator probes used). Furthermore, it will be readily appreciated that one or more mediator probes may be designed for each target nucleic acid sequence/bacterial serotype. Thus, the actual number of target nucleic acid sequences/bacterial serotypes that can be simultaneously detected by the methods of the invention can be equal to or less than the number of all mediator probes used, while still being greater than the number of detection probes used.

Thus, in certain embodiments, the invention provides a method of detecting the presence of n target nucleic acid sequences/bacterial serotypes in a sample, wherein n is an integer ≧ 2 (e.g., n is an integer of 2, 3, 4, 5,6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40 or more), and wherein the method comprises the steps of:

(3) providing m detection probes and contacting the product of step (2) with the m detection probes under conditions that allow nucleic acid hybridization,

m is an integer less than n and greater than 0, and

each detection probe independently comprises, in the 3 'to 5' direction, one or more capture sequences complementary to one or more mediator sequences or portions thereof, and a template sequence (mapping sequence); and, the m detection probes comprise a plurality (e.g., at least n) of capture sequences that are complementary to the mediator sequences, or portions thereof, respectively, of each mediator sub-probe provided in step (1); and the number of the first and second electrodes,

each detection probe is independently labeled with a reporter group and a quencher group, wherein the reporter group can emit a signal, and the quencher group can absorb or quench the signal emitted by the reporter group; and, each detection probe emits a signal when hybridized to its complement that is different from the signal when not hybridized to its complement; and the number of the first and second electrodes,

In certain preferred embodiments, each bacterial serotype is each independently selected from the group consisting of escherichia coli O serotype, escherichia coli H serotype, escherichia coli K serotype, salmonella O serotype, salmonella H serotype, vibrio parahaemolyticus O serotype, vibrio parahaemolyticus K serotype, shigella O serotype, vibrio cholerae O serotype, and the like.

Further, in steps (3) and (4) of such embodiments, when a mediator fragment corresponding to a certain target nucleic acid sequence is present, the mediator fragment hybridizes to a complementary detection probe (i.e., a detection probe containing a capture sequence complementary to the mediator sequence or a portion thereof in the mediator fragment), and the nucleic acid polymerase will extend the mediator fragment using the complementary detection probe as a template to form a duplex corresponding to the target nucleic acid sequence.

It will be readily appreciated that in the method of the invention, the m detection probes comprise a plurality of capture sequences, the collection of which encompasses the complement of the mediator sub-sequences or part thereof of all of the mediator sub-probes provided in step (1), whereby the m detection probes or the plurality of capture sequences are capable of "capturing" mediator fragments cleaved from any mediator sub-probe. That is, any mediator fragment that is cleaved from the mediator probe is capable of hybridizing to at least one detection probe or at least one capture sequence.

Still further, in step (5) of such embodiments, when a melting peak of a duplex corresponding to a certain target nucleic acid sequence is detected or not detected, the presence or absence of the target nucleic acid sequence in the sample is determined, and thereby the presence or absence of a bacterial serotype corresponding to the target nucleic acid sequence in the sample is determined.

In certain embodiments, in step (1), for each bacterial serotype to be detected, one (or more) target nucleic acid sequence(s) specific for that bacterial serotype is/are determined, and accordingly, n (or more) mediator probes are provided, each for one target nucleic acid sequence; subsequently, in step (3), the m detection probes comprise n (or more) capture sequences that are complementary to the mediator subsequences or portions, respectively, of the n (or more) mediator subsequences provided in step (1); thus, any one of the mediator fragments produced in step (2) is capable of hybridizing to at least one detection probe comprising a capture sequence complementary to a mediator sequence or part thereof in that mediator fragment and forming a duplex for subsequent extension and detection. In certain exemplary embodiments, the m detection probes comprise n capture sequences that are complementary to the mediator sequences or portions of the n mediator probes, respectively.

In certain preferred embodiments, the m detection probes do not comprise the same capture sequence as each other. In this case, for each mediator probe, there is one and only one detection probe (which contains a capture sequence complementary to the mediator subsequence in the mediator probe) that hybridizes to the mediator fragment from the mediator probe and, after the extension reaction, only one duplex is generated. Subsequently, by detecting the presence of the duplex in step (5), the presence of the target nucleic acid sequence corresponding to the mediator probe can be judged.

In certain preferred embodiments, the m detection probes may comprise the same capture sequence as each other. In this case, for each mediator probe, there may be one or more detection probes (which all comprise a capture sequence complementary to the mediator sequence in the mediator probe) that hybridize to the mediator fragment from the mediator probe and, after the extension reaction, generate one or more duplexes. Subsequently, by detecting the presence of the one or more duplexes in step (5), the presence of the target nucleic acid sequence corresponding to the mediator probe can be determined.

In step (5) of such embodiments, the duplexes may be distinguished and distinguished by their melting points and/or a reporter group in the detection probe. In certain preferred embodiments, the m detection probes comprise the same reporter group. In this case, the product of step (4) may be subjected to melting curve analysis, and the presence of a certain duplex may be determined from the melting peak (melting point) in the melting curve, and the presence of the target nucleic acid sequence corresponding to the duplex may be determined. In certain preferred embodiments, the m detection probes comprise reporter groups that are different from each other. In this case, when the product of step (4) is subjected to melting curve analysis, the signal of each reporter group can be monitored separately in real time, thereby obtaining a plurality of melting curves each corresponding to the signal of one reporter group. The presence of a duplex, and hence the target nucleic acid sequence corresponding to that duplex, can then be determined based on the signal type of the reporter and the melting peak (melting point) in the melting curve.

In certain exemplary embodiments, at least 1, at least 2, at least 3, at least 4, at least 5, at least 6, at least 8, at least 10 detection probes can be used (i.e., m is an integer of ≧ 1, ≧ 2, ≧ 3, ≧ 4, ≧ 5, ≧ 6, ≧ 8, ≧ 10). In certain exemplary embodiments, 1-10 detection probes (i.e., m is an integer from 1-10; e.g., m is 1, 2, 3, 4, 5,6, 7, 8, 9, or 10) can be used. Further preferably, the detection probes used are each labeled with a different reporter group.

For example, in certain exemplary embodiments, the methods of the present invention may use first and second detection probes that are labeled with a first reporter group and a second reporter group, respectively. Thus, in step (5), the change in the signal of the first reporter group and the second reporter group with temperature is monitored in real time, respectively, to obtain a first melting curve and a second melting curve. Subsequently, from the melting peak in the first (or second) melting curve, the presence of the duplex comprising the first (or second) detection probe can be determined, and thereby the presence of the target nucleic acid sequence corresponding to the mediator fragment hybridized to the first (or second) detection probe can be determined.

In certain exemplary embodiments, the methods of the invention employ at least 1, at least 2, at least 3, at least 4, at least 5, at least 6, at least 8, or at least 10 detection probes; and, at least 2, at least 3, at least 4, at least 5, at least 6, at least 8, at least 10, at least 15, at least 20, at least 25, at least 30, at least 35, at least 40, at least 45 mediator probes. Thus, the method of the present invention can achieve simultaneous detection (multiplex detection) of a plurality of target nucleic acid sequences, wherein the maximum number of detectable target nucleic acid sequences is equal to the number of mediator probes used.

For example, in certain exemplary embodiments, the methods of the invention achieve simultaneous detection of 2-6 (e.g., 2, 3, 4, 5, or 6) bacterial serotypes using 1 detection probe and 2-6 (e.g., 2, 3, 4, 5, or 6) mediator probes. In certain exemplary embodiments, the methods of the invention use 2 detection probes and 3-12 (e.g., 3, 4, 5,6, 7, 8, 9, 10, 11, 12) mediator probes to achieve simultaneous detection of 3-12 bacterial serotypes. In certain exemplary embodiments, the methods of the invention achieve simultaneous detection of 4-18 (e.g., 5-10) bacterial serotypes using 3 detection probes and 4-18 (e.g., 5-10) mediator probes. In certain exemplary embodiments, the methods of the invention achieve simultaneous detection of 5-24 (e.g., 6-12) bacterial serotypes using 4 detection probes and 5-24 (e.g., 6-12) mediator probes. In certain exemplary embodiments, the methods of the invention achieve simultaneous detection of 6-30 (e.g., 8-15) bacterial serotypes using 5 detection probes and 6-30 (e.g., 8-15) mediator probes. In certain exemplary embodiments, the methods of the invention achieve simultaneous detection of 7-36 (e.g., 10-18) bacterial serotypes using 6 detection probes and 7-36 (e.g., 10-18) mediator probes. In certain exemplary embodiments, the methods of the invention achieve simultaneous detection of 8-42 (e.g., 12-20, e.g., 19) bacterial serotypes using 7 detection probes and 8-42 (e.g., 12-20) mediator probes.

In certain exemplary embodiments, the detection probes used in the methods of the invention comprise: the detection probe shown as SEQ ID NO. 2, the detection probe shown as SEQ ID NO. 18, the detection probe shown as SEQ ID NO. 31, the detection probe shown as SEQ ID NO. 44, the detection probe shown as SEQ ID NO. 60, the detection probe shown as SEQ ID NO. 70, the detection probe shown as SEQ ID NO. 80, the detection probe shown as SEQ ID NO. 99, the detection probe shown as SEQ ID NO. 112, or any combination thereof.

In certain exemplary embodiments, the mediator probe used in the methods of the present invention comprises: the mediator probe shown in SEQ ID NO. 5, the mediator probe shown in SEQ ID NO. 8, the mediator probe shown in SEQ ID NO. 11, the mediator probe shown in SEQ ID NO. 14, the mediator probe shown in SEQ ID NO. 17, the mediator probe shown in SEQ ID NO. 21, the mediator probe shown in SEQ ID NO. 24, the mediator probe shown in SEQ ID NO. 27, the mediator probe shown in SEQ ID NO. 30, the mediator probe shown in SEQ ID NO. 34, the mediator probe shown in SEQ ID NO. 37, the mediator probe shown in SEQ ID NO. 40, the mediator probe shown in SEQ ID NO. 43, the mediator probe shown in SEQ ID NO. 47, the mediator probe shown in SEQ ID NO. 50, the mediator probe shown in SEQ ID NO. 53, the mediator probe shown in SEQ ID NO. 56, the mediator probe shown in SEQ ID NO. 59, the mediator probe shown in SEQ ID NO. 63, the mediator probe shown in SEQ ID NO. 66, the mediator probe shown in SEQ ID NO. 69, the mediator probe shown in SEQ ID NO. 73, the mediator probe shown in SEQ ID NO. 76, the mediator probe shown in SEQ ID NO. 79, the mediator probe shown in SEQ ID NO. 83, the mediator probe shown in SEQ ID NO. 86, the mediator probe shown in SEQ ID NO. 89, the mediator probe shown in SEQ ID NO. 92, the mediator probe shown in SEQ ID NO. 95, the mediator probe shown in SEQ ID NO. 98, the mediator probe shown in SEQ ID NO. 102, 105 as shown in SEQ ID NO, 108 as shown in SEQ ID NO, 111 as shown in SEQ ID NO, 115 as shown in SEQ ID NO, 118 as shown in SEQ ID NO, 121 as shown in SEQ ID NO, 124 as shown in SEQ ID NO, or any combination thereof.

In certain exemplary embodiments, the upstream oligonucleotide used in the methods of the invention comprises: the upstream oligonucleotide shown as SEQ ID NO. 3, the upstream oligonucleotide shown as SEQ ID NO. 6, the upstream oligonucleotide shown as SEQ ID NO. 9, the upstream oligonucleotide shown as SEQ ID NO. 12, the upstream oligonucleotide shown as SEQ ID NO. 15, the upstream oligonucleotide shown as SEQ ID NO. 19, the upstream oligonucleotide shown as SEQ ID NO. 22, the upstream oligonucleotide shown as SEQ ID NO. 25, the upstream oligonucleotide shown as SEQ ID NO. 28, the upstream oligonucleotide shown as SEQ ID NO. 32, the upstream oligonucleotide shown as SEQ ID NO. 35, the upstream oligonucleotide shown as SEQ ID NO. 38, the upstream oligonucleotide shown as SEQ ID NO. 41, the upstream oligonucleotide shown as SEQ ID NO. 45, the upstream oligonucleotide shown as SEQ ID NO. 48, the upstream oligonucleotide shown as SEQ ID NO. 51, the upstream oligonucleotide shown as SEQ ID NO. 54, the upstream oligonucleotide shown as SEQ ID NO. 57, the upstream oligonucleotide shown as SEQ ID NO. 61, the upstream oligonucleotide shown as SEQ ID NO. 64, the upstream oligonucleotide shown as SEQ ID NO. 67, the upstream oligonucleotide shown as SEQ ID NO. 71, the upstream oligonucleotide shown as SEQ ID NO. 74, the upstream oligonucleotide shown as SEQ ID NO. 77, the upstream oligonucleotide shown as SEQ ID NO. 81, the upstream oligonucleotide shown as SEQ ID NO. 84, the upstream oligonucleotide shown as SEQ ID NO. 87, the upstream oligonucleotide shown as SEQ ID NO. 90, the upstream oligonucleotide shown as SEQ ID NO. 93, the upstream oligonucleotide shown as SEQ ID NO. 96, the upstream oligonucleotide shown as SEQ ID NO. 100, the upstream oligonucleotide shown as SEQ ID NO. 103, the upstream oligonucleotide shown as SEQ ID NO. 106, the upstream oligonucleotide shown as SEQ ID NO. 109, the upstream oligonucleotide shown as SEQ ID NO. 113, the upstream oligonucleotide shown as SEQ ID NO. 116, the upstream oligonucleotide shown as SEQ ID NO. 119, the upstream oligonucleotide shown as SEQ ID NO. 122, or any combination thereof.

In certain exemplary embodiments, the methods of the invention also use a downstream oligonucleotide, and the downstream oligonucleotide used comprises: the downstream oligonucleotide shown as SEQ ID NO. 4, the downstream oligonucleotide shown as SEQ ID NO. 7, the downstream oligonucleotide shown as SEQ ID NO. 10, the downstream oligonucleotide shown as SEQ ID NO. 13, the downstream oligonucleotide shown as SEQ ID NO. 16, the downstream oligonucleotide shown as SEQ ID NO. 20, the downstream oligonucleotide shown as SEQ ID NO. 23, the downstream oligonucleotide shown as SEQ ID NO. 26, the downstream oligonucleotide shown as SEQ ID NO. 29, the downstream oligonucleotide shown as SEQ ID NO. 33, the downstream oligonucleotide shown as SEQ ID NO. 36, the downstream oligonucleotide shown as SEQ ID NO. 39, the downstream oligonucleotide shown as SEQ ID NO. 42, the downstream oligonucleotide shown as SEQ ID NO. 46, the downstream oligonucleotide shown as SEQ ID NO. 49, the downstream oligonucleotide shown as SEQ ID NO. 52, the downstream oligonucleotide shown as SEQ ID NO. 55, the downstream oligonucleotide shown as SEQ ID NO. 58, the downstream oligonucleotide shown as SEQ ID NO. 62, the downstream oligonucleotide shown as SEQ ID NO. 65, the downstream oligonucleotide shown as SEQ ID NO. 68, the downstream oligonucleotide shown as SEQ ID NO. 72, the downstream oligonucleotide shown as SEQ ID NO. 75, the downstream oligonucleotide shown as SEQ ID NO. 78, the downstream oligonucleotide shown as SEQ ID NO. 82, the downstream oligonucleotide shown as SEQ ID NO. 85, the downstream oligonucleotide shown as SEQ ID NO. 88, the downstream oligonucleotide shown as SEQ ID NO. 91, the downstream oligonucleotide shown as SEQ ID NO. 94, the downstream oligonucleotide shown as SEQ ID NO. 97, the downstream oligonucleotide shown as SEQ ID NO. 101, the downstream oligonucleotide shown as SEQ ID NO. 104, the downstream oligonucleotide shown as SEQ ID NO. 107, the downstream oligonucleotide shown as SEQ ID NO. 110, the downstream oligonucleotide shown as SEQ ID NO. 114, the downstream oligonucleotide shown as SEQ ID NO. 117, the downstream oligonucleotide shown as SEQ ID NO. 120, the downstream oligonucleotide shown as SEQ ID NO. 123, or any combination thereof.

In certain exemplary embodiments, the detection probes used in the methods of the invention comprise: 2, and the mediator probe comprises: 5 mediator probes as shown in

SEQ ID NO

5, 8, 11, 14 and 17. Preferably, the upstream oligonucleotide used in the method of the invention comprises: 3, 6, 9, 12 and 15, respectively, as shown in SEQ ID NO. More preferably, the method of the invention also uses a downstream oligonucleotide, and the downstream oligonucleotide used comprises: 5 downstream oligonucleotides as shown in

SEQ ID NO

4, 7, 10, 13 and 16, respectively. Such embodiments are useful, for example, for detecting O29, O26, O169, O161, and O126 serotypes of e.

In certain exemplary embodiments, the detection probes used in the methods of the invention comprise: 18 and the mediator probe comprises: and 4 medium sub-probes shown as

SEQ ID NO

21, 24, 27 and 30. Preferably, the upstream oligonucleotide used in the method of the invention comprises: 4 upstream oligonucleotides as shown in

SEQ ID NO

19, 22, 25 and 28, respectively. More preferably, the method of the invention also uses a downstream oligonucleotide, and the downstream oligonucleotide used comprises: 4 downstream oligonucleotides as shown in

SEQ ID NO

20, 23, 26 and 29, respectively. Such embodiments are useful, for example, for detecting O8, O143, O1, and O157 serotypes of e.

In certain exemplary embodiments, the detection probes used in the methods of the invention comprise: 31 and the mediator probe comprises: and 4 medium sub-probes shown in

SEQ ID NO

34, 37, 40 and 43 respectively. Preferably, the upstream oligonucleotide used in the method of the invention comprises: 4 upstream oligonucleotides as shown in

SEQ ID NO

32, 35, 38 and 41, respectively. More preferably, the method of the invention also uses a downstream oligonucleotide, and the downstream oligonucleotide used comprises: 33, 36, 39 and 42 of the downstream oligonucleotides. Such embodiments are useful, for example, for detecting O148, O27, O167, and O6 serotypes of e.

In certain exemplary embodiments, the detection probes used in the methods of the invention comprise: a detection probe as shown in SEQ ID NO:44, and the mediator probe used comprises: and 5 mediator probes shown in SEQ ID NO 47, 50, 53, 56 and 59. Preferably, the upstream oligonucleotide used in the method of the invention comprises: 45, 48, 51, 54 and 57, respectively. More preferably, the method of the invention also uses a downstream oligonucleotide, and the downstream oligonucleotide used comprises: 46, 49, 52, 55 and 58, respectively. Such embodiments are useful, for example, for detecting Gp6, O15, Gp13, O159, and O25 serotypes of e.

In certain exemplary embodiments, the detection probes used in the methods of the invention comprise: the detection probe shown as SEQ ID NO:60, and the medium sub-probe used comprises: 63, 66 and 69 as shown in SEQ ID NO. Preferably, the upstream oligonucleotide used in the method of the invention comprises: 3 upstream oligonucleotides shown as SEQ ID NO 61, 64 and 67, respectively. More preferably, the method of the invention also uses a downstream oligonucleotide, and the downstream oligonucleotide used comprises: and 3 downstream oligonucleotides shown in SEQ ID NO 62, 65 and 68, respectively. Such embodiments are useful, for example, for detecting O166, O91, and Gp2 serotype e.

In certain exemplary embodiments, the detection probes used in the methods of the invention comprise: 70, and the mediator probe comprises: 3 mediator probes shown in SEQ ID NO:73, 76 and 79, respectively. Preferably, the upstream oligonucleotide used in the method of the invention comprises: 71, 74 and 77, respectively. More preferably, the method of the invention also uses a downstream oligonucleotide, and the downstream oligonucleotide used comprises: 72, 75 and 78, respectively. Such embodiments may be used, for example, to detect the O86, O111 serotype e.coli, and e.coli yccT genes (used as controls).

In certain exemplary embodiments, the detection probes used in the methods of the invention comprise: 80 and the mediator probe comprises: 83, 86, 89, 92, 95 and 98 of the 6 mediator probes respectively. Preferably, the upstream oligonucleotide used in the method of the invention comprises: and 6 upstream oligonucleotides shown in SEQ ID Nos. 81, 84, 87, 90, 93 and 96. More preferably, the method of the invention also uses a downstream oligonucleotide, and the downstream oligonucleotide used comprises: 82, 85, 88, 91, 94 and 97 of SEQ ID NO. Such embodiments are useful, for example, for detecting O121, O145, O55, Gp9, O63, and O18 serotypes of e.

In certain exemplary embodiments, the detection probes used in the methods of the invention comprise: 99, and the mediator probe comprises: 4 mediator probes shown in SEQ ID NO 102, 105, 108 and 111, respectively. Preferably, the upstream oligonucleotide used in the method of the invention comprises: and 4 upstream oligonucleotides shown as SEQ ID NO 100, 103, 106 and 109, respectively. More preferably, the method of the invention also uses a downstream oligonucleotide, and the downstream oligonucleotide used comprises: 101, 104, 107 and 110, respectively. Such embodiments are useful, for example, for detecting O128, O119, O153 and O103 serotypes of e.

In certain exemplary embodiments, the detection probes used in the methods of the invention comprise: 112, and the mediator probe used comprises: 115, 118, 121 and 124 as shown in SEQ ID NO. Preferably, the upstream oligonucleotide used in the method of the invention comprises: 113, 116, 119 and 122, respectively. More preferably, the method of the invention also uses a downstream oligonucleotide, and the downstream oligonucleotide used comprises: 114, 117, 120 and 123, respectively. Such embodiments are useful, for example, for detecting O113, O104, O45, and O142 serotypes of e.

In certain exemplary embodiments, the detection probes used in the methods of the invention comprise: 2, 18, 31, 44, 60, 70, 80, 99 and 112, respectively, and the mediator sub-probes used comprise: 5, 8, 11, 14, 17, 21, 24, 27, 30, 34, 37, 40, 43, 47, 50, 53, 56, 59, 63, 66, 69, 73, 76, 79, 83, 86, 89, 92, 95, 98, 102, 105, 108, 111, 115, 118, 121 and 124. Preferably, the upstream oligonucleotide used in the method of the invention comprises: 3, 6, 9, 12, 15, 19, 22, 25, 28, 32, 35, 38, 41, 45, 48, 51, 54, 57, 61, 64, 67, 71, 74, 77, 81, 84, 87, 90, 93, 96, 100, 103, 106, 109, 113, 116, 119 and 122, respectively. More preferably, the method of the invention also uses a downstream oligonucleotide, and the downstream oligonucleotide used comprises: 4, 7, 10, 13, 16, 20, 23, 26, 29, 33, 36, 39, 42, 46, 49, 52, 55, 58, 62, 65, 68, 72, 75, 78, 82, 85, 88, 91, 94, 97, 101, 104, 107, 110, 114, 117, 120 and 123, respectively. More preferably, the method also uses a universal primer (e.g., a universal primer as shown in SEQ ID NO: 1). Such embodiments can be used, for example, for detecting Escherichia coli O29, Escherichia coli O29, Escherichia coli O26, Escherichia coli O169, Escherichia coli O161, Escherichia coli O126, Escherichia coli O8, Escherichia coli O143, Escherichia coli O1, Escherichia coli O157, Escherichia coli O148, Escherichia coli O27, Escherichia coli O167, Escherichia coli O6, Escherichia coli Gp6, Escherichia coli O15, Escherichia coli O159, Escherichia coli Gp12, Escherichia coli O25, Escherichia coli O166, Escherichia coli O91, Escherichia coli Gp2, Escherichia coli O86, Escherichia coli O111, Escherichia coli O121, Escherichia coli O145, Escherichia coli O55, Escherichia coli Gp9, Escherichia coli O63, Escherichia coli O18, Escherichia coli O128, Escherichia coli O119, Escherichia coli O153, Escherichia coli O103, Escherichia coli O113, Escherichia coli O104, Escherichia coli O45, Escherichia coli O142, or any combination thereof.

It will also be readily appreciated that various technical features described in detail for a method using one detection probe are equally applicable to a method using two or more detection probes. For example, the various details described above for the sample to be detected, the target nucleic acid sequence, the mediator probe, the upstream oligonucleotide sequence, the downstream oligonucleotide sequence, the universal primer, the detection probe, the conditions that allow for nucleic acid hybridization, the conditions that allow for cleavage of the mediator probe, the enzyme having 5' nuclease activity, the conditions that allow for extension reactions by a nucleic acid polymerase, the nucleic acid polymerase, melting curve analysis, repetition of steps, and the like, can be applied to methods using two or more detection probes. Thus, in certain preferred embodiments, the methods of the invention using two or more detection probes may involve any one or more of the features, or any combination of the features, as described in detail above.

For example, as described above, one or more of steps (1) - (4) may be repeated as desired. In certain preferred embodiments, steps (1) - (2) are repeated one or more times, and prior to each repetition, a step of nucleic acid denaturation is performed. It will be readily appreciated that the repetition of steps (1) - (2) may result in more media sub-segments for subsequent steps (i.e., steps (3) - (5)). Thus, in certain preferred embodiments, the process of the invention is carried out by the following scheme: repeating steps (1) - (2) one or more times, and prior to each repetition, performing a nucleic acid denaturation step; followed by steps (3) - (5).

(a) providing m detection probes and, for each target nucleic acid sequence to be detected, an upstream oligonucleotide sequence, a mediator probe and a downstream oligonucleotide sequence; and, optionally, providing a universal primer; wherein the detection probe, mediator probe, upstream oligonucleotide sequence, downstream oligonucleotide sequence and universal primer are as defined above;

(f) optionally, repeating steps (c) - (e) one or more times.

With respect to steps (a) - (f), these have been described in detail above.

Optional step (6) and quantitative/semi-quantitative detection

The method of the invention can be used for qualitative detection of bacterial serotype and quantitative or semi-quantitative detection of bacterial serotype content. It will be readily appreciated that when a certain bacterial serotype is present in a higher amount in a sample, the specific target nucleic acid sequence is present in a higher amount, and accordingly, the more mediator probes hybridize to the target nucleic acid sequence in step (1); furthermore, the more mediator sub-probes are cut in the step (2), the more mediator fragments are released; furthermore, in steps (3) and (4), the more mediator fragments that hybridize to the detection probe, the more duplexes that are generated by the extension reaction; furthermore, in step (5), the more duplexes that can be subjected to melting curve analysis, the stronger the signal generated, and the higher the height of the melting peak obtained. Thus, by the relative height of the melting peaks, the content/level of the corresponding bacterial serotype in the sample can be judged (quantitative or semi-quantitative detection). Thus, the methods of the invention can be used to detect not only the presence of two or more bacterial serotypes in a sample, but also the level of the two or more bacterial serotypes in a sample.

Thus, in certain preferred embodiments, the method of the present invention further comprises the steps of:

(6) from the results of the melting curve analysis (in particular, the peak heights of the melting peaks in the melting curve), the levels of the bacterial serotypes corresponding to the respective melting peaks were determined.

Probe set and kit

In another aspect, the present invention provides a probe set (probe set) comprising a detection probe and at least two mediator probes, wherein,

each of said mediator probes independently comprises in the 5 'to 3' direction a mediator subsequence comprising a sequence complementary to a target nucleic acid sequence or a control sequence specific to a bacterial serotype and a target-specific sequence comprising a sequence not complementary to said target nucleic acid sequence or control sequence, and all mediator subsequences are different from each other; and

the detection probe comprises, in the 3 'to 5' direction, a capture sequence complementary to each mediator sequence or a portion thereof, and a template sequence (templating sequence); and the detection probe is labeled with a reporter group and a quencher group, wherein the reporter group can emit a signal, and the quencher group can absorb or quench the signal emitted by the reporter group; and wherein the detection probe emits a signal when hybridized to its complement that is different from the signal when not hybridized to its complement.

In certain preferred embodiments, each target is each independently selected from the group consisting of escherichia coli serotype O, escherichia coli serotype H, escherichia coli serotype K, salmonella serotype O, salmonella serotype H, vibrio parahaemolyticus serotype O, vibrio parahaemolyticus serotype K, shigella serotype O, vibrio cholerae serotype O, and the like.

In certain preferred embodiments, the set of probes comprises at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, at least 10, at least 12, at least 15, or at least 20 mediator probes.

It will be readily appreciated that such a set of probes may be used to carry out the methods of the invention as described in detail above. Thus, the various technical features detailed above for the mediator and detection probes are equally applicable to the mediator and detection probes in the probe set. Thus, in certain preferred embodiments, the set of probes comprises a mediator probe as defined above. In certain preferred embodiments, the set of probes comprises detection probes as defined above.

In certain preferred embodiments, all mediator probes each target a different target nucleic acid sequence. In certain preferred embodiments, all of the mediator sequences contained in the mediator probes are different from each other; furthermore, all mediator probes contain target-specific sequences that are different from each other. In certain preferred embodiments, the different target nucleic acid sequences may each be specific for the same or different bacterial serotypes. In certain preferred embodiments, at least one mediator probe (or the target-specific sequence it comprises) targets a control sequence. In certain preferred embodiments, the control sequence is a sequence that does not include a bacterial antigen gene, such as the e.coli yccT gene. In certain preferred embodiments, the control sequence is a host-specific sequence, such as a human-specific sequence. In certain preferred embodiments, the control sequence is the gene sequence of human ribonuclease P.

In certain preferred embodiments, the panel of probes comprises 2, 3, 4, 5,6, 7, 8, 9, 10 or more mediator probes. Preferably, the media probe (or target-specific sequence comprised by it) targets a specific nucleic acid sequence of 2, 3, 4, 5,6, 7, 8, 9, 10 or more bacterial serotypes. In certain exemplary embodiments, the bacterial serotypes include, but are not limited to, Escherichia coli O29, Escherichia coli O29, Escherichia coli O26, Escherichia coli O169, Escherichia coli O161, Escherichia coli O126, Escherichia coli O8, Escherichia coli O143, Escherichia coli O1, Escherichia coli O157, Escherichia coli O148, Escherichia coli O27, Escherichia coli O167, Escherichia coli O6, Escherichia coli Gp6, Escherichia coli O15, Escherichia coli O159, Escherichia coli Gp12, Escherichia coli O25, Escherichia coli O166, Escherichia coli O91, Escherichia coli Gp2, Escherichia coli O86, Escherichia coli O111, Escherichia coli O121, Escherichia coli O145, Escherichia coli O55, Escherichia coli Gp9, Escherichia coli O63, Escherichia coli O18, Escherichia coli O128, Escherichia coli O119, Escherichia coli O39153, Escherichia coli O103, Escherichia coli O113, Escherichia coli O104, Escherichia coli O45, Escherichia coli O142, or any combination thereof.

In certain embodiments of the invention, the at least one bacterial serotype is selected from the group consisting of e.coli type O29, e.coli type O29, e.coli type O26, e.coli type O169, e.coli type O161, e.coli type O126, e.coli type O8, e.coli type O143, e.coli type O1, e.coli type O157, e.coli type O148, e.coli type O27, e.coli type O167, e.coli type O6, e.coli type Gp6, e.coli type O15, e.coli type O159, e.coli type Gp12, e.coli type O25, e.coli type O166, e.coli type O91, e.coli type Gp2, e.coli type O86, e.coli type O111, e.coli type O121, e.coli type O145, e.coli type O55, e.coli type Gp9, e.coli type O63, e.coli type O18, e.coli type O128, e.coli, Escherichia coli O113, Escherichia coli O104, Escherichia coli O45, and Escherichia coli O142.

In certain preferred embodiments, the probe set comprises 1 detection probe, and 2-6 (e.g., 2, 3, 4, 5, or 6) mediator probes. Thus, the panel of probes can be used to detect 2-6 (e.g., 2, 3, 4, 5 or 6) bacterial serotypes simultaneously.

In certain preferred embodiments, the set of probes further comprises an upstream oligonucleotide sequence as defined above. For example, an upstream oligonucleotide sequence comprising a sequence complementary to the target nucleic acid sequence can be provided for each target nucleic acid sequence and mediator probe; and, when hybridized to the target nucleic acid sequence, the upstream oligonucleotide sequence is located upstream of the target-specific sequence of the mediator probe.

In certain preferred embodiments, the set of probes further comprises a downstream oligonucleotide sequence as defined above. For example, a downstream oligonucleotide sequence comprising a sequence complementary to the target nucleic acid sequence can be provided for each target nucleic acid sequence and mediator probe; and, when hybridized to the target nucleic acid sequence, the downstream oligonucleotide sequence is located downstream of the target-specific sequence of the mediator probe.

In certain preferred embodiments, the probe set further comprises a universal primer as defined above. For example, in certain preferred embodiments, the upstream oligonucleotide sequence and the downstream oligonucleotide sequence comprise an identical oligonucleotide sequence at the 5' end; thus, the probe set may further comprise a universal primer having a sequence complementary to the same oligonucleotide sequence.

In certain preferred embodiments, the set of probes further comprises an upstream oligonucleotide sequence and a downstream oligonucleotide sequence as defined above. In certain preferred embodiments, the probe set further comprises an upstream oligonucleotide sequence, a downstream oligonucleotide sequence and a universal primer as defined above.

In certain exemplary embodiments, the set of probes comprises detection probes selected from the group consisting of: the detection probe shown as SEQ ID NO. 2, the detection probe shown as SEQ ID NO. 18, the detection probe shown as SEQ ID NO. 31, the detection probe shown as SEQ ID NO. 44, the detection probe shown as SEQ ID NO. 60, the detection probe shown as SEQ ID NO. 70, the detection probe shown as SEQ ID NO. 80, the detection probe shown as SEQ ID NO. 99, the detection probe shown as SEQ ID NO. 112, or any combination thereof.

In certain exemplary embodiments, the set of probes comprises a mediator probe selected from the group consisting of: the mediator probe shown in SEQ ID NO. 5, the mediator probe shown in SEQ ID NO. 8, the mediator probe shown in SEQ ID NO. 11, the mediator probe shown in SEQ ID NO. 14, the mediator probe shown in SEQ ID NO. 17, the mediator probe shown in SEQ ID NO. 21, the mediator probe shown in SEQ ID NO. 24, the mediator probe shown in SEQ ID NO. 27, the mediator probe shown in SEQ ID NO. 30, the mediator probe shown in SEQ ID NO. 34, the mediator probe shown in SEQ ID NO. 37, the mediator probe shown in SEQ ID NO. 40, the mediator probe shown in SEQ ID NO. 43, the mediator probe shown in SEQ ID NO. 47, the mediator probe shown in SEQ ID NO. 50, the mediator probe shown in SEQ ID NO. 53, the mediator probe shown in SEQ ID NO. 56, the mediator probe shown in SEQ ID NO. 59, the mediator probe shown in SEQ ID NO. 63, the mediator probe shown in SEQ ID NO. 66, the mediator probe shown in SEQ ID NO. 69, the mediator probe shown in SEQ ID NO. 73, the mediator probe shown in SEQ ID NO. 76, the mediator probe shown in SEQ ID NO. 79, the mediator probe shown in SEQ ID NO. 83, the mediator probe shown in SEQ ID NO. 86, the mediator probe shown in SEQ ID NO. 89, the mediator probe shown in SEQ ID NO. 92, the mediator probe shown in SEQ ID NO. 95, the mediator probe shown in SEQ ID NO. 98, the mediator probe shown in SEQ ID NO. 102, 105 as shown in SEQ ID NO, 108 as shown in SEQ ID NO, 111 as shown in SEQ ID NO, 115 as shown in SEQ ID NO, 118 as shown in SEQ ID NO, 121 as shown in SEQ ID NO, 124 as shown in SEQ ID NO or any combination thereof.

In certain exemplary embodiments, the set of probes further comprises an upstream oligonucleotide selected from the group consisting of: the upstream oligonucleotide shown as SEQ ID NO. 3, the upstream oligonucleotide shown as SEQ ID NO. 6, the upstream oligonucleotide shown as SEQ ID NO. 9, the upstream oligonucleotide shown as SEQ ID NO. 12, the upstream oligonucleotide shown as SEQ ID NO. 15, the upstream oligonucleotide shown as SEQ ID NO. 19, the upstream oligonucleotide shown as SEQ ID NO. 22, the upstream oligonucleotide shown as SEQ ID NO. 25, the upstream oligonucleotide shown as SEQ ID NO. 28, the upstream oligonucleotide shown as SEQ ID NO. 32, the upstream oligonucleotide shown as SEQ ID NO. 35, the upstream oligonucleotide shown as SEQ ID NO. 38, the upstream oligonucleotide shown as SEQ ID NO. 41, the upstream oligonucleotide shown as SEQ ID NO. 45, the upstream oligonucleotide shown as SEQ ID NO. 48, the upstream oligonucleotide shown as SEQ ID NO. 51, the upstream oligonucleotide shown as SEQ ID NO. 54, the upstream oligonucleotide shown as SEQ ID NO. 57, the upstream oligonucleotide shown as SEQ ID NO. 61, the upstream oligonucleotide shown as SEQ ID NO. 64, the upstream oligonucleotide shown as SEQ ID NO. 67, the upstream oligonucleotide shown as SEQ ID NO. 71, the upstream oligonucleotide shown as SEQ ID NO. 74, the upstream oligonucleotide shown as SEQ ID NO. 77, the upstream oligonucleotide shown as SEQ ID NO. 81, the upstream oligonucleotide shown as SEQ ID NO. 84, the upstream oligonucleotide shown as SEQ ID NO. 87, the upstream oligonucleotide shown as SEQ ID NO. 90, the upstream oligonucleotide shown as SEQ ID NO. 93, the upstream oligonucleotide shown as SEQ ID NO. 96, the upstream oligonucleotide shown as SEQ ID NO. 100, the upstream oligonucleotide shown as SEQ ID NO. 103, the upstream oligonucleotide shown as SEQ ID NO. 106, the upstream oligonucleotide shown as SEQ ID NO. 109, the upstream oligonucleotide shown as SEQ ID NO. 113, the upstream oligonucleotide shown as SEQ ID NO. 116, the upstream oligonucleotide shown as SEQ ID NO. 119, the upstream oligonucleotide shown as SEQ ID NO. 122, or any combination thereof.

In certain exemplary embodiments, the set of probes further comprises a downstream oligonucleotide selected from the group consisting of: the downstream oligonucleotide shown as SEQ ID NO. 4, the downstream oligonucleotide shown as SEQ ID NO. 7, the downstream oligonucleotide shown as SEQ ID NO. 10, the downstream oligonucleotide shown as SEQ ID NO. 13, the downstream oligonucleotide shown as SEQ ID NO. 16, the downstream oligonucleotide shown as SEQ ID NO. 20, the downstream oligonucleotide shown as SEQ ID NO. 23, the downstream oligonucleotide shown as SEQ ID NO. 26, the downstream oligonucleotide shown as SEQ ID NO. 29, the downstream oligonucleotide shown as SEQ ID NO. 33, the downstream oligonucleotide shown as SEQ ID NO. 36, the downstream oligonucleotide shown as SEQ ID NO. 39, the downstream oligonucleotide shown as SEQ ID NO. 42, the downstream oligonucleotide shown as SEQ ID NO. 46, the downstream oligonucleotide shown as SEQ ID NO. 49, the downstream oligonucleotide shown as SEQ ID NO. 52, the downstream oligonucleotide shown as SEQ ID NO. 55, the downstream oligonucleotide shown as SEQ ID NO. 58, the downstream oligonucleotide shown as SEQ ID NO. 62, the downstream oligonucleotide shown as SEQ ID NO. 65, the downstream oligonucleotide shown as SEQ ID NO. 68, the downstream oligonucleotide shown as SEQ ID NO. 72, the downstream oligonucleotide shown as SEQ ID NO. 75, the downstream oligonucleotide shown as SEQ ID NO. 78, the downstream oligonucleotide shown as SEQ ID NO. 82, the downstream oligonucleotide shown as SEQ ID NO. 85, the downstream oligonucleotide shown as SEQ ID NO. 88, the downstream oligonucleotide shown as SEQ ID NO. 91, the downstream oligonucleotide shown as SEQ ID NO. 94, the downstream oligonucleotide shown as SEQ ID NO. 97, the downstream oligonucleotide shown as SEQ ID NO. 101, the downstream oligonucleotide shown as SEQ ID NO. 104, the downstream oligonucleotide shown as SEQ ID NO. 107, the downstream oligonucleotide shown as SEQ ID NO. 110, the downstream oligonucleotide shown as SEQ ID NO. 114, the downstream oligonucleotide shown as SEQ ID NO. 117, the downstream oligonucleotide shown as SEQ ID NO. 120, the downstream oligonucleotide shown as SEQ ID NO. 123, or any combination thereof.

In certain exemplary embodiments, the set of probes (hereinafter referred to simply as the first set of probes for ease of distinction and description) comprises: a detection probe shown as SEQ ID NO. 2, and 5 medium sub-probes shown as SEQ ID NO. 5, 8, 11, 14 and 17 respectively. Preferably, the first set of probes further comprises: 3, 6, 9, 12 and 15, respectively, as shown in SEQ ID NO. More preferably, the first set of probes further comprises: 5 downstream oligonucleotides as shown in

SEQ ID NO

4, 7, 10, 13 and 16, respectively. Such probe sets can be used, for example, to detect O29, O26, O169, O161, and O126 serotypes of e.

In certain exemplary embodiments, the set of probes (hereinafter referred to simply as the second set of probes for ease of distinction and description) comprises: a detection probe shown as SEQ ID NO. 18, and 4 medium sub-probes shown as SEQ ID NO. 21, 24, 27 and 30 respectively. Preferably, the second set of probes further comprises: 4 upstream oligonucleotides as shown in

SEQ ID NO

19, 22, 25 and 28, respectively. More preferably, the second set of probes further comprises: 4 downstream oligonucleotides as shown in

SEQ ID NO

20, 23, 26 and 29, respectively. Such probe sets can be used, for example, to detect O8, O143, O1, and O157 serotypes of e.

In certain exemplary embodiments, the set of probes (hereinafter referred to simply as the third set of probes for ease of distinction and description) comprises: a detection probe shown as SEQ ID NO. 31, and 4 medium sub-probes shown as SEQ ID NO. 34, 37, 40 and 43 respectively. Preferably, the third set of probes further comprises: 4 upstream oligonucleotides as shown in

SEQ ID NO

32, 35, 38 and 41, respectively. More preferably, the third set of probes further comprises: 33, 36, 39 and 42 of the downstream oligonucleotides. Such probe sets can be used, for example, to detect O148, O27, O167, and O6 serotypes of e.

In certain exemplary embodiments, the set of probes (hereinafter referred to simply as the fourth set of probes for ease of distinction and description) comprises: a detection probe shown as SEQ ID NO. 44, and 5 medium sub-probes shown as SEQ ID NO. 47, 50, 53, 56 and 59 respectively. Preferably, the fourth set of probes further comprises: 45, 48, 51, 54 and 57, respectively. More preferably, the fourth set of probes further comprises: 46, 49, 52, 55 and 58, respectively. Such probe sets can be used, for example, to detect Gp6, O15, Gp13, O159, and O25 serotypes of e.

In certain exemplary embodiments, the set of probes (hereinafter referred to simply as the fifth set of probes for ease of distinction and description) comprises: a detection probe shown as SEQ ID NO. 60, and 3 kinds of vector sub-probes shown as SEQ ID NO. 63, 66 and 69 respectively. Preferably, the fifth set of probes further comprises: 3 upstream oligonucleotides shown as SEQ ID NO 61, 64 and 67, respectively. More preferably, the fifth set of probes further comprises: and 3 downstream oligonucleotides shown in SEQ ID NO 62, 65 and 68, respectively. Such probe sets can be used, for example, to detect O166, O91, and Gp2 serotypes of e.

In certain exemplary embodiments, the set of probes (hereinafter referred to as the sixth set of probes for ease of distinction and description) comprises: a detection probe shown as SEQ ID NO. 70, and 3 medium sub-probes shown as SEQ ID NO. 73, 76 and 79 respectively. Preferably, the sixth set of probes further comprises: 71, 74 and 77, respectively. More preferably, the sixth set of probes further comprises: 72, 75 and 78, respectively. Such a probe set can be used, for example, to detect the O86, O111 serotype e.coli and e.coli yccT gene (used as a control).

In certain exemplary embodiments, the set of probes (hereinafter referred to as the seventh set of probes for ease of distinction and description) comprises: a detection probe shown as SEQ ID NO. 80, and 6 mediator probes shown as SEQ ID NO. 83, 86, 89, 92, 95 and 98 respectively. Preferably, the seventh set of probes further comprises: 81, 84, 87, 90, 93 and 96 of SEQ ID NO. More preferably, the seventh probe set further comprises: 82, 85, 88, 91, 94 and 97 of SEQ ID NO. Such probe sets can be used, for example, to detect O121, O145, O55, Gp9, O63, and O18 serotypes of E.coli.

In certain exemplary embodiments, the set of probes (hereinafter referred to simply as the eighth set of probes for ease of distinction and description) comprises: a detection probe shown as SEQ ID NO. 99, and 4 medium sub-probes shown as SEQ ID NO. 102, 105, 108 and 111 respectively. Preferably, the eighth set of probes further comprises: and 4 upstream oligonucleotides shown as SEQ ID NO 100, 103, 106 and 109, respectively. More preferably, the eighth set of probes further comprises: 101, 104, 107 and 110, respectively. Such probe sets can be used, for example, to detect O128, O119, O153 and O103 serotypes of e.

In certain exemplary embodiments, the set of probes (hereinafter referred to simply as the ninth set of probes for ease of distinction and description) comprises: 112, and 4 mediator probes shown in SEQ ID NO 115, 118, 121 and 124. Preferably, the ninth set of probes further comprises: 113, 116, 119 and 122, respectively. More preferably, the ninth probe set further comprises: 114, 117, 120 and 123, respectively. Such probe sets can be used, for example, to detect O113, O104, O45, and O142 serotypes of e.

In certain preferred embodiments, a probe set of the invention further comprises a universal primer (e.g., a universal primer as set forth in SEQ ID NO: 1). For example, the first, second, third, fourth, fifth, sixth, seventh, eighth, and/or ninth probe set described above may comprise a universal primer as set forth in SEQ ID NO. 1.

In another aspect, the invention provides a kit comprising one or more sets of probes as defined above.

In certain preferred embodiments, the kit comprises at least 1, at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, at least 10 probe sets.

In certain preferred embodiments, all of the mediator sequences in the kit are each targeted to a different target nucleic acid sequence. In certain preferred embodiments, all of the mediator probes in the kit comprise a mediator sequence that is different from each other. In certain preferred embodiments, all of the mediator probes in the kit comprise target-specific sequences that are different from each other.

In certain preferred embodiments, all of the detection probes in the kit comprise the same reporter group. In certain preferred embodiments, all of the detection probes in the kit are each independently labeled with the same or different reporter groups. In certain preferred embodiments, all of the detection probes in the kit comprise a reporter group that is different from each other.

In certain exemplary embodiments, the kit comprises: 9 detection probes as set forth in

SEQ ID NOs

2, 18, 31, 44, 60, 70, 80, 99 and 112, respectively, and 38 mediator probes as set forth in

SEQ ID NOs

5, 8, 11, 14, 17, 21, 24, 27, 30, 34, 37, 40, 43, 47, 50, 53, 56, 59, 63, 66, 69, 73, 76, 79, 83, 86, 89, 92, 95, 98, 102, 105, 108, 111, 115, 118, 121 and 124, respectively. Preferably, the kit further comprises: 3, 6, 9, 12, 15, 19, 22, 25, 28, 32, 35, 38, 41, 45, 48, 51, 54, 57, 61, 64, 67, 71, 74, 77, 81, 84, 87, 90, 93, 96, 100, 103, 106, 109, 113, 116, 119 and 122, respectively. More preferably, the kit further comprises: 4, 7, 10, 13, 16, 20, 23, 26, 29, 33, 36, 39, 42, 46, 49, 52, 55, 58, 62, 65, 68, 72, 75, 78, 82, 85, 88, 91, 94, 97, 101, 104, 107, 110, 114, 117, 120 and 123, respectively. More preferably, the kit further comprises a universal primer (e.g., a universal primer as shown in SEQ ID NO: 1). Such a kit can be used for detecting, for example, Escherichia coli O29, Escherichia coli O29, Escherichia coli O26, Escherichia coli O169, Escherichia coli O161, Escherichia coli O126, Escherichia coli O8, Escherichia coli O143, Escherichia coli O1, Escherichia coli O157, Escherichia coli O148, Escherichia coli O27, Escherichia coli O167, Escherichia coli O6, Escherichia coli Gp6, Escherichia coli O15, Escherichia coli O159, Escherichia coli Gp12, Escherichia coli O25, Escherichia coli O166, Escherichia coli O91, Escherichia coli Gp2, Escherichia coli O86, Escherichia coli O111, Escherichia coli O121, Escherichia coli O145, Escherichia coli O55, Escherichia coli Gp9, Escherichia coli O63, Escherichia coli O18, Escherichia coli O128, Escherichia coli O119, Escherichia coli O153, Escherichia coli O103, Escherichia coli O113, Escherichia coli O104, Escherichia coli O45, Escherichia coli O142, or any combination thereof.

In certain preferred embodiments, the kit comprises 1-9 probe sets. Preferably, all detection probes in the kit comprise reporter groups that are the same or different from each other. Further preferably, all of the mediator probes in the kit comprise different mediator sequences from each other, and all of the mediator probes in the kit comprise different target-specific sequences from each other.

In certain preferred embodiments, the kit comprises one or more of the first to ninth probe sets described above, e.g., 1, 2, 3, 4, 5,6, 7, 8, or 9.

The present application also provides a kit comprising m detection probes and n mediator sub-probes, wherein n is an integer ≧ 2 (e.g., n is an integer of 2, 3, 4, 5,6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, or more), m is an integer less than n and greater than 0, and,

each mediator probe independently comprises, in the 5 'to 3' direction, a mediator subsequence comprising a sequence complementary to a target nucleic acid sequence or a control sequence specific to a bacterial serotype and a target-specific sequence comprising a sequence not complementary to the target nucleic acid sequence or the control sequence, and all mediator subsequences are different from each other; and

each detection probe independently comprises, in the 3 'to 5' direction, one or more capture sequences complementary to one or more mediator sequences or portions thereof, and a template sequence (mapping sequence); and, the m detection probes comprise a plurality (e.g., at least n) of capture sequences that are complementary to the mediator sequences, or portions thereof, of each mediator probe, respectively; and the number of the first and second electrodes,

each detection probe is independently labeled with a reporter group and a quencher group, wherein the reporter group can emit a signal, and the quencher group can absorb or quench the signal emitted by the reporter group; and, each detection probe emits a signal when hybridized to its complement that is different from the signal when not hybridized to its complement.

In certain preferred embodiments, each bacterial serotype is each independently selected from the group consisting of Escherichia coli serotype O, Escherichia coli serotype H, Escherichia coli serotype K, Salmonella serotype O, Salmonella serotype H, Vibrio parahaemolyticus serotype O, Vibrio parahaemolyticus serotype K, Shigella serotype O, Vibrio cholerae serotype O, and the like.

In an exemplary embodiment of the invention, the m detection probes comprise a plurality of capture sequences, the collection of said plurality of capture sequences encompassing the complement of the mediator sub-sequences or part thereof of all the mediator sub-probes provided in step (1), whereby said m detection probes or said plurality of capture sequences are capable of "capturing" mediator fragments cleaved from any mediator sub-probe. That is, any mediator fragment that is cleaved from the mediator probe is capable of hybridizing to at least one detection probe or at least one capture sequence.

In certain exemplary embodiments, the kit comprises at least 1, at least 2, at least 3, at least 4, at least 5, at least 6, at least 8, at least 10 detection probes (i.e., m is an integer of ≧ 1, ≧ 2, ≧ 3, ≧ 4, ≧ 5, ≧ 6, ≧ 8, ≧ 10). In certain exemplary embodiments, the kit comprises 1-10 detection probes (i.e., m is an integer from 1-10; e.g., m is 1, 2, 3, 4, 5,6, 7, 8, 9, or 10). Further preferably, the detection probes are each labeled with the same or different reporter groups.

In certain exemplary embodiments, the kit comprises at least 1, at least 2, at least 3, at least 4, at least 5, at least 6, at least 8, or at least 10 detection probes; and, at least 2, at least 3, at least 4, at least 5, at least 6, at least 8, at least 10, at least 15, at least 20, at least 25, at least 30, at least 35, at least 40, at least 45 mediator probes. Thus, the kit can be used to simultaneously detect multiple target nucleic acid sequences/bacterial serotypes, where the maximum number of detectable target nucleic acid sequences/bacterial serotypes is equal to the number of mediator probes used.

For example, in certain exemplary embodiments, the kit comprises 1 detection probe and 2-6 (e.g., 2, 3, 4, 5, or 6) mediator probes, and can be used to simultaneously detect 2-6 (e.g., 2, 3, 4, 5, or 6) bacterial serotypes. In certain exemplary embodiments, the kit comprises 2 detection probes and 3-12 (e.g., 3, 4, 5,6, 7, 8, 9, 10, 11, 12) mediator probes, which can be used to simultaneously detect 3-12 bacterial serotypes. In certain exemplary embodiments, the kit comprises 3 detection probes and 4-18 (e.g., 5-10) mediator probes, and can be used to simultaneously detect 4-18 (e.g., 5-10) bacterial serotypes. In certain exemplary embodiments, the kit comprises 4 detection probes and 5-24 (e.g., 6-12) mediator probes, and can be used to simultaneously detect 5-24 (e.g., 6-12) bacterial serotypes. In certain exemplary embodiments, the kit comprises 5 detection probes and 6-30 (e.g., 8-15) mediator probes, and can be used to simultaneously detect 6-30 (e.g., 8-15) bacterial serotypes. In certain exemplary embodiments, the kit comprises 6 detection probes and 7-36 (e.g., 10-18) mediator probes, and can be used to simultaneously detect 7-36 (e.g., 10-18) bacterial serotypes. In certain exemplary embodiments, the kit comprises 7 detection probes and 8-42 (e.g., 12-20) mediator probes, and can be used to simultaneously detect 8-42 (e.g., 12-20, e.g., 19) bacterial serotypes.

It will be readily appreciated that such kits may be used to carry out the methods of the invention as described in detail above. Thus, the various technical features detailed above for the mediator and detection probes are equally applicable to the mediator and detection probes in the kit. Also, such kits may further comprise other reagents necessary to carry out the methods of the invention.

For example, in certain preferred embodiments, the kit may further comprise an upstream oligonucleotide sequence, a downstream oligonucleotide sequence, a universal primer, an enzyme having 5' nuclease activity, a nucleic acid polymerase, or any combination thereof, as defined above. In certain preferred embodiments, the kit may further comprise reagents for performing nucleic acid hybridization, reagents for performing mediator probe cleavage, reagents for performing nucleic acid extension, reagents for performing nucleic acid amplification, reagents for performing reverse transcription, or any combination thereof. Such reagents can be routinely determined by one of skill in the art and include, but are not limited to, working buffers for enzymes (e.g., nucleic acid polymerases), dNTPs, water, inclusion ions (e.g., Mg)²⁺) A Single Strand DNA-Binding Protein (SSB), or any combination thereof. For example, reagents for performing reverse transcription include, but are not limited to, reverse transcriptase working buffer, Oligo d (T), dNTPs, nuclease-free water, RNase inhibitors, or any combination thereof.

Use of probe set

The present application also relates to the use of a set of probes as defined above for the preparation of a kit for detecting the presence or level of a bacterial serotype in a sample or for diagnosing whether a subject is infected with said bacterial serotype.

It will be readily appreciated that the set of probes or kit may be used to carry out the methods of the invention as described in detail above. Thus, the various technical features detailed above with respect to bacterial serotypes, probe sets, kits, and the various components contained therein (e.g., mediator probes, detection probes, upstream oligonucleotide sequences, downstream oligonucleotide sequences, universal primers, enzymes with 5' nuclease activity, nucleic acid polymerases, reagents for performing nucleic acid hybridization, reagents for performing mediator probe cleavage, reagents for performing nucleic acid extension, reagents for performing nucleic acid amplification, reagents for performing reverse transcription, or any combination thereof) are equally applicable thereto.

Those skilled in the art may make modifications, substitutions or combinations of various features of the invention based on the principles described in detail herein without departing from the spirit and scope of the invention. All such variations and modifications are intended to be included herein within the scope of the following claims and their equivalents.

Advantageous effects of the invention

Compared with the prior art, the technical scheme of the invention has the following beneficial effects:

(1) the methods, probe sets, and kits of the invention enable the simultaneous detection (multiplex detection) of multiple target nucleic acid sequences/bacterial serotypes (e.g., escherichia coli O serotype, escherichia coli H serotype, escherichia coli K serotype, salmonella O serotype, salmonella H serotype, vibrio parahaemolyticus O serotype, vibrio parahaemolyticus K serotype, shigella O serotype, vibrio cholerae O serotype, etc.) using only one labeled probe (i.e., detection probe).

(2) The method of the present invention can achieve simultaneous detection (multiplex detection) of a plurality of target nucleic acid sequences/bacterial serotypes (e.g., escherichia coli O serotype, escherichia coli H serotype, escherichia coli K serotype, salmonella O serotype, salmonella H serotype, vibrio parahaemolyticus O serotype, vibrio parahaemolyticus K serotype, shigella O serotype, vibrio cholerae O serotype, etc.), and the maximum number of target nucleic acid sequences/bacterial serotypes that can be detected simultaneously far exceeds the number of label probes (i.e., detection probes) used.

Thus, the present invention provides a simple, highly efficient, low cost multiplex assay capable of simultaneously detecting multiple bacterial serotypes (e.g., E.coli serotype O, E.coli serotype H, E.coli serotype K, Salmonella serotype O, Salmonella serotype H, Vibrio parahaemolyticus serotype O, Vibrio parahaemolyticus serotype K, Shigella serotype O, Vibrio cholerae serotype O, etc.). The maximum number of target nucleic acid sequences/bacterial serotypes that can be detected by the methods of the invention is not limited by the number of label probes (i.e., detection probes) used. That is, the methods of the invention enable simultaneous detection (multiplex detection) of a significantly greater number of target nucleic acid sequences/bacterial serotypes based on a relatively limited number of labeled probes (i.e., detection probes), which is particularly advantageous.

Embodiments of the present invention will be described in detail below with reference to the drawings and examples, but those skilled in the art will understand that the following drawings and examples are only for illustrating the present invention and do not limit the scope of the present invention. Various objects and advantageous aspects of the present invention will become apparent to those skilled in the art from the accompanying drawings and the following detailed description of the preferred embodiments.

Drawings

Fig. 1 schematically depicts an exemplary embodiment of the method of the invention to illustrate the basic principle of the method of the invention.

FIG. 1A schematically depicts an exemplary embodiment of the use of 1 detection probe and 5 mediator probes to detect 5 target nucleic acid molecules (each specific for, e.g., one bacterial serotype). In this embodiment, a self-quenching detection probe (which carries a fluorescent group and a quenching group) is provided, and an upstream primer (upstream primer 1-5), a downstream primer (downstream primer 1-5), and a mediator probe (mediator probe 1-5) are designed and provided separately for each target nucleic acid molecule (T1-T5); wherein each mediator probe comprises a unique mediator sequence (mediator sequences 1-5) that is capable of hybridizing to the detection probe. The position at which each mediator sequence hybridises to the detection probe is unique, but there may be regions of overlap with each other. For example, as shown in FIG. 1A, the hybridization position of the mediator subsequence 1 on the detection probe overlaps with the mediator subsequence 2, the hybridization position of the mediator subsequence 4 on the detection probe overlaps with the mediator subsequence 5, and the hybridization position of the mediator subsequence 3 on the detection probe overlaps with other mediatorsThere is no overlap of subsequences. In the detection process, 5 kinds of upstream primers, 5 kinds of downstream primers and 5 kinds of mediator probes are respectively hybridized (annealed) with the corresponding target nucleic acid molecules; subsequently, all the forward primers and the reverse primers are respectively extended under the action of nucleic acid polymerase, and the extension of each forward primer (forward primer 1-5) causes the corresponding mediator probe (mediator probe 1-5) to be cleaved by an enzyme having 5' nuclease activity, thereby releasing the mediator fragment (mediator fragment 1-5); subsequently, the vector subsections 1-5 are hybridized to different positions of the detection probe, respectively, and extended by nucleic acid polymerase, thereby generating 5 extension products; the 5 extension products each have a different length and together with the detection probe form 5 extension products with different T_mValue duplexes. From this, it can be confirmed that the melting curve has a specific T_mThe presence of a duplex of values, and thus the presence of a target nucleic acid molecule corresponding to the duplex, can be determined. Thus, in the methods of the invention, detection of 5 target nucleic acid molecules (and the 5 bacterial serotypes corresponding thereto) can be achieved using 1 detection probe and 5 mediator probes.

FIG. 1B schematically depicts an exemplary embodiment of the use of 2 detection probes and 10 mediator probes to detect 10 target nucleic acid molecules (T1-T10, each specific for one bacterial serotype, for example). In this embodiment, two self-quenching detection probes (first and second detection probes) are provided, each carrying a different fluorophore (fluorophore 1-2) and a different quencher (quencher 1-2); and designing and providing an upstream primer (upstream primer 1-10), a downstream primer (downstream primer 1-10) and a mediator probe (mediator probe 1-10) for each target nucleic acid molecule (T1-T10); wherein each of the mediator probes comprises a unique mediator subsequence (mediator subsequences 1-10), and the mediator subsequences 1-5 are capable of hybridizing to the first detection probe and the mediator subsequences 6-10 are capable of hybridizing to the second detection probe. The position of hybridization of each mediator sequence to the detection probe is unique, but there may be overlapping regions with each other. For example, as shown in FIG. 1B, the mediator sequence 1 is hybridized to the first detection probeThe cross position is overlapped with the medium subsequence 2, the cross position of the medium subsequence 4 on the first detection probe is overlapped with the medium subsequence 5, and the cross position of the medium subsequence 3 on the first detection probe is not overlapped with other medium subsequences; the hybridization position of the vector subsequence 6 on the second detection probe is overlapped with the vector subsequence 7, the hybridization position of the vector subsequence 9 on the second detection probe is overlapped with the vector subsequence 10, and the hybridization position of the vector subsequence 8 on the second detection probe is not overlapped with other vector subsequences. In the detection process, 10 kinds of upstream primers, 10 kinds of downstream primers and 10 kinds of mediator probes are respectively hybridized (annealed) with the corresponding target nucleic acid molecules; subsequently, all the forward primers and the reverse primers are respectively extended under the action of nucleic acid polymerase, and the extension of each forward primer (forward primer 1-10) causes the corresponding mediator probe (mediator probe 1-10) to be cleaved by an enzyme having 5' nuclease activity, thereby releasing the mediator fragment (mediator fragment 1-10); subsequently, the vector subsections 1-5 are hybridized to different positions of the first detection probe, respectively, and extended by nucleic acid polymerase, thereby generating 5 extension products; the 5 extension products each have a different length and together with the first detection probe form 5 extension products with different T_mValue duplexes. Similarly, the vector subsegments 6-10 hybridize to different positions on the second detection probe, respectively, and are extended by the nucleic acid polymerase, thereby generating 5 additional extension products; the 5 extension products each have a different length and together with the second detection probe form another 5 extension products having a different T_mValue duplexes. Subsequently, melting curve analysis was performed using fluorophores (fluorophores 1-2) on the first and second detection probes, respectively, to determine that the probe has a specific T_mThe presence of a duplex of values, and thus the presence of a target nucleic acid molecule corresponding to the duplex, can be determined. Thus, in the methods of the invention, detection of 10 target nucleic acid molecules (and the 10 bacterial serotypes corresponding thereto) can be achieved using 2 detection probes and 10 mediator probes.

FIG. 2 shows the results of the detection of a sample containing Escherichia coli O157 using the reagents described in Table 1 and the detection scheme described in Table 2.

FIG. 3 shows the results of testing samples containing 38 bacterial serotypes using the reagents described in Table 1 and the testing protocol described in Table 2.

Sequence information

Table 1: sequence information of SEQ ID NOS 1-124

Note: the base preceded by a "+" is a base modified by Locked Nucleic Acid (LNA); and W, S, K, R, M, Y has a meaning well known in the art (i.e., W ═ a or T; S ═ G or C; K ═ G or T; R ═ a or G; M ═ a or C; Y ═ C or T).

Detailed Description

The invention will now be described with reference to the following examples, which are intended to illustrate the invention, but not to limit it. It is to be understood that these embodiments are merely illustrative of the principles and technical effects of the present invention, and do not represent all possibilities for the invention. The present invention is not limited to the materials, reaction conditions or parameters mentioned in these examples. Other embodiments may be practiced by those skilled in the art using other similar materials or reaction conditions in accordance with the principles of the invention. Such solutions do not depart from the basic principles and concepts described herein, and are intended to be within the scope of the invention.

The details of the detection probes, mediator probes, upstream oligonucleotides (upstream primers), downstream oligonucleotides (downstream primers), and universal primers used in the examples of the present application, as well as their working concentrations and detection targets, are summarized in table 1. By using the reagents provided in table 1 (i.e., 9 detection probes, 38 mediator probes, 38 upstream oligonucleotides (upstream primers), 38 downstream oligonucleotides (downstream primers), and 1 universal primer), the method of the invention enables simultaneous detection of 37 bacterial serotypes and 1 control sequence (thirty-eight fold detection) using only 9 fluorescent probes (detection probes). The fluorescence detection channels used and melting points of the melting peaks detected are summarized in table 2.

Among the various detection probes and mediator probes described in Table 1, detection probes 1 and 2 are labeled with ROX and BHQ2, and the fluorescent signals thereof are detected through the ROX channel; the detection probes 3 and 4 are labeled with FAM and BHQ1, and fluorescent signals of the probes are detected through a FAM channel; the detection probes 5 and 6 are labeled with Cy5 and BHQ2, and fluorescent signals of the detection probes are detected through a Cy5 channel; the detection probe 7 is labeled with HEX and BHQ1, and the fluorescence signal of the detection probe is detected through a HEX channel.

The mediator sequences in 5 mediator probes shown in

SEQ ID NOS

5, 8, 11, 14 and 17, respectively, are each capable of binding to detection probe 1, and the 5 mediator probes are used for detecting O29, O26, O169, O161 and O126 serotypes of E.coli, respectively. The mediator sequences in the 4 mediator probes shown in SEQ ID NOS: 21, 24, 27 and 30, respectively, are each capable of binding to the detection probe 2, and the 4 mediator probes are used for detecting Escherichia coli serotypes O8, O143, O1 and O157, respectively. The mediator sequences in the 4 mediator probes shown in SEQ ID NOS: 34, 37, 40 and 43, respectively, are each capable of binding to the detection probe 3, and the 4 mediator probes are used for detecting Escherichia coli serotypes O148, O27, O167 and O6, respectively. The mediator sequences in the 5 mediator probes respectively shown in SEQ ID NOS: 47, 50, 53, 56 and 59 are each capable of binding to the detection probe 4, and the 5 mediator probes are used for detecting serotype Gp6, O15, Gp13, O159 and O25 E.coli, respectively. The mediator sequences in the 3 mediator probes shown in SEQ ID NOS: 63, 66 and 69, respectively, are each capable of binding to the detection probe 5, and the 3 mediator probes are used for detecting O166, O91 and Gp2 serotypes of E.coli, respectively. The mediator sequences in the 3 mediator probes shown in SEQ ID NOS: 73, 76, and 79, respectively, are each capable of binding to the detection probe 6, and these 3 mediator probes are used for detecting O86, serotype O111 E.coli, and E.coli yccT genes, respectively (used as controls). 83, 86, 89, 92, 95 and 98 respectively, and 6 mediator sub-probes are used for detecting O121, O145, O55, Gp9, O63 and O18 serotypes of Escherichia coli. The mediator sequences in the 4 mediator sub-probes shown in SEQ ID NOS: 102, 105, 108 and 111, respectively, are each capable of binding to the detection probe 8, and the 4 mediator sub-probes are used for detecting O128, O119, O153 and O103 serotypes of E.coli, respectively. The mediator subsequences of the 4 mediator probes shown in SEQ ID NOS: 34, 37, 40 and 43, respectively, are each capable of binding to the detection probe 9, and the 4 mediator probes are used for detecting O113, O104, O45 and O142 serotypes of E.coli, respectively.

Table 2: detection scheme

Example 1 detection of O157 serotype E.coli

In this example, samples containing O157 serotype E.coli were tested using the reagents described in Table 1 (9 detection probes, 38 mediator probes, 38 forward primers, 38 downstream primers, and 1 universal primer) and the test protocol described in Table 2.

Briefly, in this example, real-time PCR was performed using a 25 μ L PCR reaction system comprising: 1 XPCR buffer (67mM Tris-HCl,50mM KCl and 0.085mg/mL BSA), 6.0mM MgCl₂0.2mM dNTPs, 2.0U of polymerase TaqHS (Takara), various reagents described in Table 1 (used at the indicated working concentrations), and 5. mu.L of O157 serotype E.coli DNA. The reaction conditions of the real-time PCR are as follows: 95 ℃ for 5 min; then 50 cycles (95 ℃, 20s and 63 ℃, 1 min). After completion of PCR, melting curve analysis was performed according to the following procedure: at 95 ℃ for 2 min; at 40 ℃ for 2 min; the temperature of the reaction system was then raised from 40 ℃ to 95 ℃ at a ramp rate of 0.4 ℃/step (the holding time per step was 5s), and the fluorescence signals of the ROX, FAM, HEX and Cy5 channels were collected during this process. The laboratory instrument used was a Bio-Rad CFX96 real-time PCR instrument (Bio-Rad, USA). The results of the detection are shown in FIG. 2.

The results in FIG. 2 show that in the fluorescence signal collected from the Quasar channel, a characteristic melting peak corresponding to E.coli serotype O157 was observed at 84.3 ℃; in the fluorescence signal collected from the Cy5 channel, a characteristic melting peak corresponding to the control DNA was observed at 85.4 ℃; also, no melting peak was observed in the fluorescence signals collected by the ROX, HEX and FAM channels. The result shows that the designed detection system can be used for specifically detecting O157 serotype Escherichia coli.

Example 2 thirty-eight tests

In this example, 37 bacterial serotypes (from Escherichia coli O29, Escherichia coli O29, Escherichia coli O26, Escherichia coli O169, Escherichia coli O161, Escherichia coli O126, Escherichia coli O8, Escherichia coli O143, Escherichia coli O1, Escherichia coli O157, Escherichia coli O148, Escherichia coli O27, Escherichia coli O167, Escherichia coli O6, Escherichia coli Gp6, Escherichia coli O15, Escherichia coli O159, Escherichia coli Gp12, Escherichia coli O25, Escherichia coli O166, Escherichia coli O91, Escherichia coli Gp2, Escherichia coli O86, Escherichia coli O111, Escherichia coli O121, Escherichia coli O145, Escherichia coli) were tested using the reagents described in Table 1 (9 detection probes, 38 medium probes, 38 forward primers, 38 backward primers, and 1 universal primer) and the detection protocol described in Table 2, DNA of Escherichia coli O55, Escherichia coli Gp9, Escherichia coli O63, Escherichia coli O18, Escherichia coli O128, Escherichia coli O119, Escherichia coli O153, Escherichia coli O103, Escherichia coli O113, Escherichia coli O104, Escherichia coli O45, and Escherichia coli O142), and a control DNA (Escherichia coli yccT gene).

Briefly, in this example, real-time PCR was performed using a 25 μ L PCR reaction system comprising: 1 XPCR buffer (67mM Tris-HCl,50mM KCl and 0.085mg/mL BSA), 6.0mM MgCl₂0.2mM dNTPs, 2.0U polymerase TaqHS (Takara), various reagents described in Table 1 (used at the indicated working concentrations), and 5 μ L of a nucleic acid mixture comprising the 37 bacterial serotype DNAs and a control DNA (e.coli yccT gene). 95 ℃ for 5 min; then 50 cycles (95 ℃, 20s and 63 ℃, 1 min.) after PCR, melting curve analysis was performed according to the following procedure: at 95 ℃ for 2 min; at 40 ℃ for 2 min; subsequently, the temperature of the reaction system was raised from 40 ℃ to 95 ℃ at a temperature raising rate of 0.4 ℃/step (the holding time per step was 5 seconds), fluorescence signals of ROX, FAM, HEX and Cy5 channels were collected during this procedure, the used experimental instrument was a Bio-Rad CFX96 real-time PCR instrument (Bio-Rad, USA), and the results of the detection are shown in FIG. 3.

The results in FIG. 3 show that 9 characteristic melting peaks (peaks 1 to 9) corresponding to Escherichia coli O29, Escherichia coli O29, Escherichia coli O26, Escherichia coli O169, Escherichia coli O161, Escherichia coli O126, Escherichia coli O8, Escherichia coli O143, Escherichia coli O1 and Escherichia coli O157 were observed at 56.3 ℃, 61.3 ℃, 65.2 ℃, 67.7 ℃, 70.2 ℃, 74.3 ℃, 76.6 ℃, 80.7 ℃ and 84.3 ℃ in the fluorescence signal collected from the Quasar channel; in the fluorescence signal collected by the ROX channel, 9 characteristic melting peaks (peaks 10 to 18) corresponding to Escherichia coli O148, Escherichia coli O27, Escherichia coli O167, Escherichia coli O6, Escherichia coli Gp6, Escherichia coli O15, Escherichia coli O159, Escherichia coli Gp12 and Escherichia coli O25 were observed at 56.5 ℃, 61.5 ℃, 64.5 ℃, 67.5 ℃, 70.5 ℃, 74.5 ℃, 77.2 ℃, 79.3 ℃ and 86.3 ℃ respectively; in the fluorescence signal collected by the Cy5 channel, 6 characteristic melting peaks (peaks 19 to 24) corresponding to Escherichia coli O166, Escherichia coli O91, Escherichia coli Gp2, Escherichia coli O86, Escherichia coli O111 and the internal standard gene were observed at 62.0 ℃, 66.5 ℃, 70.6 ℃, 74.3 ℃, 79.9 ℃ and 85.4 ℃ respectively; in the fluorescence signal collected by the HEX channel, 10 characteristic melting peaks (peaks 25 to 34) corresponding to Escherichia coli O121, Escherichia coli O145, Escherichia coli O55, Escherichia coli Gp9, Escherichia coli O63, Escherichia coli O18, Escherichia coli O128, Escherichia coli O119, Escherichia coli O153 and Escherichia coli O103 were observed at 53.7 ℃, 59.5 ℃, 61.9 ℃, 64.9 ℃, 67.6 ℃, 70.1 ℃, 74.5 ℃, 78.7 ℃, 82.7 ℃ and 85.1 ℃ respectively; in addition, in the fluorescence signal collected by the FAM channel, 4 characteristic melting peaks (peaks 35 to 38) corresponding to Escherichia coli O113, Escherichia coli O104, Escherichia coli O45 and Escherichia coli O142 were observed at 65.5 ℃, 70.6 ℃, 75.3 ℃ and 79.2 ℃. This result indicates that the designed detection system can be used to specifically detect the 37 bacterial serotypes, and can accurately distinguish the 37 bacterial serotypes from the control.

These experimental results show that with the designed detection system and reagents (especially the designed 38 vector sub-probes and 7 fluorescent probes), simultaneous detection and discrimination of 38 target sequences (37 bacterial serotypes and 1 control) can be achieved in a single assay (i.e., thirty-eight detection). Thus, the methods and kits of the invention can be used to rapidly, easily, sensitively, specifically, stably, and reliably detect multiple bacterial serotypes (e.g., 37 or more bacterial serotypes) simultaneously.

While specific embodiments of the invention have been described in detail, those skilled in the art will understand that: various modifications and changes in detail can be made in light of the overall teachings of the disclosure, and such changes are intended to be within the scope of the present invention. The full scope of the invention is given by the appended claims and any equivalents thereof.

SEQUENCE LISTING

<110> university of mansion

<120> a method for detecting bacterial serotypes

<130>IDC180262

<160>124

<170>PatentIn version 3.5

<210>1

<211>20

<212>DNA

<213> Artificial sequence

<220>

<223> Universal primer

<400>1

gcaagccctc acgtagcgaa 20

<210>2

<211>39

<212>DNA

<213> Artificial sequence

<220>

<223> detection Probe 1

<400>2

aagcccaata caacagcagt actactggca tgagggctt 39

<210>3

<211>40

<212>DNA

<213> Artificial sequence

<220>

<223> O29 upstream primer

<400>3

gcaagccctc acgtagcgaa tcgttggttt agttttggca 40

<210>4

<211>38

<212>DNA

<213> Artificial sequence

<220>

<223> O29 downstream primer

<400>4

gcaagccctc acgtagcgaa gtcaagcctg gtgctaat 38

<210>5

<211>50

<212>DNA

<213> Artificial sequence

<220>

<223> O29 medium sub-probe

<400>5

gctgttgtat tggtatagtc aggatgatta tgctggatca gtacttacgt 50

<210>6

<211>40

<212>DNA

<213> Artificial sequence

<220>

<223> O26 upstream primer

<400>6

gcaagccctc acgtagcgaa atgcacaggt tatcatctgt 40

<210>7

<211>43

<212>DNA

<213> Artificial sequence

<220>

<223> O26 downstream primer

<400>7

gcaagccctc acgtagcgaa ttctccaact ttgtatggtt cta 43

<210>8

<211>31

<212>DNA

<213> Artificial sequence

<220>

<223> O26 medium sub-probe

<400>8

tactgctgtt ggcgaagcaa gagtgccaag a 31

<210>9

<211>38

<212>DNA

<213> Artificial sequence

<220>

<223> O169 upstream primer

<400>9

gcaagccctc acgtagcgaa gccggttcaa caatcgta 38

<210>10

<211>43

<212>DNA

<213> Artificial sequence

<220>

<223> O169 downstream primer

<400>10

gcaagccctc acgtagcgaa tccgaaaaaa tacttggtaagga 43

<210>11

<211>38

<212>DNA

<213> Artificial sequence

<220>

<223> O169 medium probe

<400>11

agtagtactg acgcagcgac agaatatact ccaacact 38

<210>12

<211>39

<212>DNA

<213> Artificial sequence

<220>

<223> O161 upstream primer

<400>12

gcaagccctc acgtagcgaa cctttaccag ctccctcat 39

<210>13

<211>42

<212>DNA

<213> Artificial sequence

<220>

<223> O161 downstream primer

<400>13

gcaagccctc acgtagcgaa gaagagcatt ggagaatgat ga 42

<210>14

<211>46

<212>DNA

<213> Artificial sequence

<220>

<223> O161 media probe

<400>14

ccagtagtac ggatattcgg ttgcagttca aatatctctt gtgtct 46

<210>15

<211>43

<212>DNA

<213> Artificial sequence

<220>

<223> O126 upstream primer

<400>15

gcaagccctc acgtagcgaa tataaatggg ggtatcacat agc 43

<210>16

<211>38

<212>DNA

<213> Artificial sequence

<220>

<223> O126 downstream primer

<400>16

gcaagccctc acgtagcgaa ctcttatcaa gccacgca 38

<210>17

<211>47

<212>DNA

<213> Artificial sequence

<220>

<223> O126 media probe

<400>17

tcatgccagt gcagatatta gtggatgaat cgccactaat cctaacg 47

<210>18

<211>47

<212>DNA

<213> Artificial sequence

<220>

<223> detection Probe 2

<400>18

gcgcgccgaa ctcaccgagc tgacagcatgcagcaccgag ggcgcgc 47

<210>19

<211>39

<212>DNA

<213> Artificial sequence

<220>

<223> O8 upstream primer

<400>19

gcaagccctc acgtagcgaa atccttggtg tgatgaacg 39

<210>20

<211>39

<212>DNA

<213> Artificial sequence

<220>

<223> O8 downstream primer

<400>20

gcaagccctc acgtagcgaa tgataggcga agatggact 39

<210>21

<211>46

<212>DNA

<213> Artificial sequence

<220>

<223> O8 medium sub-probe

<400>21

ctcggtgagt tcagtacata aacaatgggt gtgaaccaaa accaga 46

<210>22

<211>37

<212>DNA

<213> Artificial sequence

<220>

<223> O143 upstream primer

<400>22

gcaagccctc acgtagcgaa tggcctgcat gctcttt 37

<210>23

<211>39

<212>DNA

<213> Artificial sequence

<220>

<223> O143 downstream primer

<400>23

gcaagccctc acgtagcgaa cctaatcccc tgatgcctc 39

<210>24

<211>43

<212>DNA

<213> Artificial sequence

<220>

<223> O143 media probe

<400>24

cagctcggtg ctctgttata attgcgtcgc acttaatcca gca 43

<210>25

<211>42

<212>DNA

<213> Artificial sequence

<220>

<223> O1 upstream primer

<400>25

gcaagccctc acgtagcgaa acaatgctgg ctatatgatg at 42

<210>26

<211>37

<212>DNA

<213> Artificial sequence

<220>

<223> O1 downstream primer

<400>26

gcaagccctc acgtagcgaa gcttgcacag gcaaaag 37

<210>27

<211>43

<212>DNA

<213> Artificial sequence

<220>

<223> O1 medium sub-probe

<400>27

gcatgctgtc attctgtgag atcgcacgac ttgcactaaa aga 43

<210>28

<211>40

<212>DNA

<213> Artificial sequence

<220>

<223> O157 upstream primer

<400>28

gcaagccctc acgtagcgaa atatgtggga acatttggag 40

<210>29

<211>39

<212>DNA

<213> Artificial sequence

<220>

<223> O157 downstream primer

<400>29

gcaagccctc acgtagcgaa cctataacgt catgccaat 39

<210>30

<211>47

<212>DNA

<213> Artificial sequence

<220>

<223> O157 media probe

<400>30

tcggtgctgc actttatgac cgttgtttac attttaaagg ccaagga 47

<210>31

<211>35

<212>DNA

<213> Artificial sequence

<220>

<223> detection Probe 3

<400>31

cgagcaatca acatgaagca gtcgactgag gctcg 35

<210>32

<211>41

<212>DNA

<213> Artificial sequence

<220>

<223> O148 upstream primer

<400>32

gcaagccctc acgtagcgaa tttgtatttg gactgttcgc t 41

<210>33

<211>36

<212>DNA

<213> Artificial sequence

<220>

<223> O148 downstream primer

<400>33

gcaagccctc acgtagcgaa attttcgggg agcgtg 36

<210>34

<211>44

<212>DNA

<213> Artificial sequence

<220>

<223> O148 medium probe

<400>34

cttcatgttg atgccaatcc cgagaaaaga taaaccctta acgt 44

<210>35

<211>41

<212>DNA

<213> Artificial sequence

<220>

<223> O27 upstream primer

<400>35

gcaagccctc acgtagcgaa atctactttt ggaagcgaac a 41

<210>36

<211>38

<212>DNA

<213> Artificial sequence

<220>

<223> O27 downstream primer

<400>36

gcaagccctc acgtagcgaa tgcgacgcca aatgtaaa 38

<210>37

<211>43

<212>DNA

<213> Artificial sequence

<220>

<223> O27 medium sub-probe

<400>37

ctgcttcatg tcagaactaa cccataaata gcacaggatc ccg 43

<210>38

<211>45

<212>DNA

<213> Artificial sequence

<220>

<223> O167 upstream primer

<400>38

gcaagccctc acgtagcgaa gcactaagct ttgtagttta tacgt 45

<210>39

<211>44

<212>DNA

<213> Artificial sequence

<220>

<223> O167 downstream primer

<400>39

gcaagccctc acgtagcgaa tagagacaaa aaggaactaa tgct 44

<210>40

<211>39

<212>DNA

<213> Artificial sequence

<220>

<223> O167 medium probe

<400>40

gactgcttca ggtcaggggc aattacaatc cttgctagc 39

<210>41

<211>43

<212>DNA

<213> Artificial sequence

<220>

<223> O6 upstream primer

<400>41

gcaagccctc acgtagcgaa tgtgcgtttc atatacagtt cag 43

<210>42

<211>42

<212>DNA

<213> Artificial sequence

<220>

<223> O6 downstream primer

<400>42

gcaagccctc acgtagcgaa aaatcattgt aatcagcaga cg 42

<210>43

<211>44

<212>DNA

<213> Artificial sequence

<220>

<223> O6 medium sub-probe

<400>43

gtcgactgct ttatagcttc actacgacta cccttcaagg tgct 44

<210>44

<211>59

<212>DNA

<213> Artificial sequence

<220>

<223> detection Probe 4

<400>44

cggcggacgt acgacagcat gacgagctag cgatggctgc cgagcgactg ccaccgccg 59

<210>45

<211>44

<212>DNA

<213> Artificial sequence

<220>

<223> Gp6 upstream primer

<400>45

gcaagccctc acgtagcgaa aaaatctctg caatttttga ctgt 44

<210>46

<211>40

<212>DNA

<213> Artificial sequence

<220>

<223> Gp6 downstream primer

<400>46

gcaagccctc acgtagcgaa ggaaatatgg gacaggccat 40

<210>47

<211>47

<212>DNA

<213> Artificial sequence

<220>

<223> Gp6 mediator probe

<400>47

tgctgtcgta cggcttcggt tttttagcat gtacactgtc taaaacg 47

<210>48

<211>42

<212>DNA

<213> Artificial sequence

<220>

<223> O15 upstream primer

<400>48

gcaagccctc acgtagcgaa gctatttctc ttgtcccact at 42

<210>49

<211>39

<212>DNA

<213> Artificial sequence

<220>

<223> O15 downstream primer

<400>49

gcaagccctc acgtagcgaa gccaattacc tactgccat 39

<210>50

<211>50

<212>DNA

<213> Artificial sequence

<220>

<223> O15 medium sub-probe

<400>50

cgtcatgctg tgttagagtc attggtgtat cgaattttgg tgatctgagt 50

<210>51

<211>40

<212>DNA

<213> Artificial sequence

<220>

<223> Gp13 upstream primer

<400>51

gcaagccctc acgtagcgaa tttacattcg tagtcaccgc 40

<210>52

<211>43

<212>DNA

<213> Artificial sequence

<220>

<223> Gp13 downstream primer

<400>52

gcaagccctc acgtagcgaa actgcaacca aatataacac act 43

<210>53

<211>40

<212>DNA

<213> Artificial sequence

<220>

<223> Gp13 media probe

<400>53

ctagctcgtc agtatgtctt cttttggcaa ggggggtgat 40

<210>54

<211>38

<212>DNA

<213> Artificial sequence

<220>

<223> O159 upstream primer

<400>54

gcaagccctc acgtagcgaa gtaacgctcg tcacatcg 38

<210>55

<211>44

<212>DNA

<213> Artificial sequence

<220>

<223> O159 downstream primer

<400>55

gcaagccctc acgtagcgaa accaaacttc gaaaaaaaac ctag 44

<210>56

<211>46

<212>DNA

<213> Artificial sequence

<220>

<223> O159 media probe

<400>56

catcgctagc tacgcccaaa tccattactg cttttaatga ccatgc 46

<210>57

<211>38

<212>DNA

<213> Artificial sequence

<220>

<223> O25 upstream primer

<400>57

gcaagccctc acgtagcgaa ggggggtact attgctct 38

<210>58

<211>42

<212>DNA

<213> Artificial sequence

<220>

<223> O25 downstream primer

<400>58

gcaagccctc acgtagcgaa acaagcactg ataagttcgt ag 42

<210>59

<211>50

<212>DNA

<213> Artificial sequence

<220>

<223> O25 medium sub-probe

<400>59

ggcagtcgct caatgcctac taacatcgtt aagttctgga tacctaacgc 50

<210>60

<211>35

<212>DNA

<213> Artificial sequence

<220>

<223> detection Probe 5

<400>60

gctgcaaatc agctgactac agtcgacaga gcagc 35

<210>61

<211>40

<212>DNA

<213> Artificial sequence

<220>

<223> O166 upstream primer

<400>61

gcaagccctc acgtagcgaa tcaggatgag atgatgggaa 40

<210>62

<211>43

<212>DNA

<213> Artificial sequence

<220>

<223> O166 downstream primer

<400>62

gcaagccctc acgtagcgaa ccctgataca attccagttg ata 43

<210>63

<211>51

<212>DNA

<213> Artificial sequence

<220>

<223> O166 media probe

<400>63

tagtcagctg atgctgtaag gaataacaac tgcattctca tcattattgg a 51

<210>64

<211>41

<212>DNA

<213> Artificial sequence

<220>

<223> O91 upstream primer

<400>64

gcaagccctc acgtagcgaa catgctgctc attcttctca t 41

<210>65

<211>43

<212>DNA

<213> Artificial sequence

<220>

<223> O91 downstream primer

<400>65

gcaagccctc acgtagcgaa atattcctga gaacaacagt gag 43

<210>66

<211>42

<212>DNA

<213> Artificial sequence

<220>

<223> O91 medium sub-probe

<400>66

gactgtagtc agtttgcaac aaacaaaaat agcgtcgcag ca 42

<210>67

<211>41

<212>DNA

<213> Artificial sequence

<220>

<223> Gp2 upstream primer

<400>67

gcaagccctc acgtagcgaa ccattaccga ttatccagtg t 41

<210>68

<211>38

<212>DNA

<213> Artificial sequence

<220>

<223> Gp2 downstream primer

<400>68

gcaagccctc acgtagcgaa atgattgacc atcccagg 38

<210>69

<211>45

<212>DNA

<213> Artificial sequence

<220>

<223> Gp2 mediator probe

<400>69

tgtcgactgt agcaacatag tttgcataag cgggaaaact tagca 45

<210>70

<211>51

<212>DNA

<213> Artificial sequence

<220>

<223> detection Probe 6

<400>70

ccggcgggag agatcgcagt cgaggagcag ccagtggcag tgcgccgccg g 51

<210>71

<211>42

<212>DNA

<213> Artificial sequence

<220>

<223> O86 upstream primer

<400>71

gcaagccctc acgtagcgaa gtaacgacca tttcttcact ga 42

<210>72

<211>39

<212>DNA

<213> Artificial sequence

<220>

<223> O86 downstream primer

<400>72

gcaagccctc acgtagcgaa cttccaatga tccacccaa 39

<210>73

<211>49

<212>DNA

<213> Artificial sequence

<220>

<223> O86 medium sub-probe

<400>73

gactgcgatc tctcctcctt ctttaaaata aacaccacga gcgatgtca 49

<210>74

<211>43

<212>DNA

<213> Artificial sequence

<220>

<223> O111 upstream primer

<400>74

gcaagccctc acgtagcgaa gtcaatccaa tttgcatctt cat 43

<210>75

<211>43

<212>DNA

<213> Artificial sequence

<220>

<223> O111 downstream primer

<400>75

gcaagccctc acgtagcgaa taggaaattt gacgtaaagc att 43

<210>76

<211>46

<212>DNA

<213> Artificial sequence

<220>

<223> O111 medium probe

<400>76

tgctcctcga caatccatgc ggaacatcct ccacatatta actgag 46

<210>77

<211>41

<212>DNA

<213> Artificial sequence

<220>

<223> E.coli upstream primer

<400>77

gcaagccctc acgtagcgaa tacagccgtt cttcactatt g 41

<210>78

<211>44

<212>DNA

<213> Artificial sequence

<220>

<223> E.coli downstream primer

<400>78

gcaagccctc acgtagcgaa tcattatttc ctccagactg ttta 44

<210>79

<211>41

<212>DNA

<213> Artificial sequence

<220>

<223> Medium sub-Probe

<400>79

gcactgccac ttatgtttgc cggtatccgt ttttgccacc a 41

<210>80

<211>41

<212>DNA

<213> Artificial sequence

<220>

<223> detection Probe 7

<400>80

atcgccataa cacagagtca tgagagactg catcaggcga t 41

<210>81

<211>42

<212>DNA

<213> Artificial sequence

<220>

<223> O121 upstream primer

<400>81

gcaagccctc acgtagcgaa agctcagctt ttatcttgtt ca 42

<210>82

<211>38

<212>DNA

<213> Artificial sequence

<220>

<223> O121 downstream primer

<400>82

gcaagccctc acgtagcgaa acataggctc ccaaccat 38

<210>83

<211>48

<212>DNA

<213> Artificial sequence

<220>

<223> O121 medium probe

<400>83

ctctgtgtta tcatacctta atatataaag ccatccaacc acgcccgt 48

<210>84

<211>40

<212>DNA

<213> Artificial sequence

<220>

<223> O145 upstream primer

<400>84

gcaagccctc acgtagcgaa gacaggagtt attgtaggca 40

<210>85

<211>38

<212>DNA

<213> Artificial sequence

<220>

<223> O145 downstream primer

<400>85

gcaagccctc acgtagcgaa cgctgaataa gcaccact 38

<210>86

<211>39

<212>DNA

<213> Artificial sequence

<220>

<223> O145 medium probe

<400>86

tgactctgtg tcccatcagt ggcagcccaa tatgaaacc 39

<210>87

<211>43

<212>DNA

<213> Artificial sequence

<220>

<223> O55 upstream primer

<400>87

gcaagccctc acgtagcgaa acgtctaatt attagcggaa ctt 43

<210>88

<211>39

<212>DNA

<213> Artificial sequence

<220>

<223> O55 downstream primer

<400>88

gcaagccctc acgtagcgaa caaaagcacc acgctatct 39

<210>89

<211>38

<212>DNA

<213> Artificial sequence

<220>

<223> O55 medium sub-probe

<400>89

tcatgactct gtgtgataat tggcagcttt cctggcgg 38

<210>90

<211>40

<212>DNA

<213> Artificial sequence

<220>

<223> Gp9 upstream primer

<400>90

gcaagccctc acgtagcgaa tcgtatttcc gtgaagggta 40

<210>91

<211>37

<212>DNA

<213> Artificial sequence

<220>

<223> Gp9 downstream primer

<400>91

gcaagccctc acgtagcgaa cacagcggga tgaagtt 37

<210>92

<211>43

<212>DNA

<213> Artificial sequence

<220>

<223> Gp9 mediator probe

<400>92

tctcatgact ctgcatatca aacaaattct gcatcccccc aag 43

<210>93

<211>42

<212>DNA

<213> Artificial sequence

<220>

<223> O63 upstream primer

<400>93

gcaagccctc acgtagcgaa gtgctttttt aggtatggga gt 42

<210>94

<211>43

<212>DNA

<213> Artificial sequence

<220>

<223> O63 downstream primer

<400>94

gcaagccctc acgtagcgaa actaggtttg agaattacag cca 43

<210>95

<211>49

<212>DNA

<213> Artificial sequence

<220>

<223> O63 medium sub-probe

<400>95

cagtctctca tcaagaggca atgtctttat gacaatagtt acgtgctca 49

<210>96

<211>41

<212>DNA

<213> Artificial sequence

<220>

<223> O18 upstream primer

<400>96

gcaagccctc acgtagcgaa agtattcaat cccgaggtca t 41

<210>97

<211>42

<212>DNA

<213> Artificial sequence

<220>

<223> O18 downstream primer

<400>97

gcaagccctc acgtagcgaa atacttaccg tccaaaagac tt 42

<210>98

<211>37

<212>DNA

<213> Artificial sequence

<220>

<223> O18 medium sub-probe

<400>98

tgatgcagtc caacaacccc atgtgctttt atgaggt 37

<210>99

<211>55

<212>DNA

<213> Artificial sequence

<220>

<223> detection Probe 8

<400>99

cgcgcgatcg agcatacgat gacgacagct gagcgagcct gaggtcgcac gcgcg 55

<210>100

<211>39

<212>DNA

<213> Artificial sequence

<220>

<223> O128 upstream primer

<400>100

gcaagccctc acgtagcgaa cgatcgtctt gttcaggtt 39

<210>101

<211>40

<212>DNA

<213> Artificial sequence

<220>

<223> O128 downstream primer

<400>101

gcaagccctc acgtagcgaa gaatgcaatg ggcaattaac 40

<210>102

<211>37

<212>DNA

<213> Artificial sequence

<220>

<223> O128 mediator probe

<400>102

tgtcgtcatc ggaggccaat tgtgcaaccc caatagc 37

<210>103

<211>38

<212>DNA

<213> Artificial sequence

<220>

<223> O119 upstream primer

<400>103

gcaagccctc acgtagcgaa gctgatgcta ttgacgga 38

<210>104

<211>41

<212>DNA

<213> Artificial sequence

<220>

<223> O119 downstream primer

<400>104

gcaagccctc acgtagcgaa aaagcaggta aaactgtgac a 41

<210>105

<211>38

<212>DNA

<213> Artificial sequence

<220>

<223> O119 mediator probe

<400>105

gctcagctgt caggaaagca gattgcccca gtattgca 38

<210>106

<211>43

<212>DNA

<213> Artificial sequence

<220>

<223> O153 upstream primer

<400>106

gcaagccctc acgtagcgaa cgattttaga gcacagttga atg 43

<210>107

<211>39

<212>DNA

<213> Artificial sequence

<220>

<223> O153 downstream primer

<400>107

gcaagccctc acgtagcgaa actcttctcg attccgaca 39

<210>108

<211>43

<212>DNA

<213> Artificial sequence

<220>

<223> O153 medium probe

<400>108

tcaggctcgc caatcaggcc gctatctata tataccccac cca 43

<210>109

<211>40

<212>DNA

<213> Artificial sequence

<220>

<223> O103 upstream primer

<400>109

gcaagccctc acgtagcgaa gggcttgtat tgttgtaccg 40

<210>110

<211>38

<212>DNA

<213> Artificial sequence

<220>

<223> O103 downstream primer

<400>110

gcaagccctc acgtagcgaa cgcagaaaat ccccgata 38

<210>111

<211>36

<212>DNA

<213> Artificial sequence

<220>

<223> O103 medium probe

<400>111

tgcgacctca gctcccgagc acgtataaag tcagcc 36

<210>112

<211>53

<212>DNA

<213> Artificial sequence

<220>

<223> detection Probe 9

<400>112

gcgcgccata atgagtgtgc tagtacgacg tcacactgca ggtgcaggcg cgc 53

<210>113

<211>39

<212>DNA

<213> Artificial sequence

<220>

<223> O113 upstream primer

<400>113

gcaagccctc acgtagcgaa agaatggatg gggggtatg 39

<210>114

<211>40

<212>DNA

<213> Artificial sequence

<220>

<223> O113 downstream primer

<400>114

gcaagccctc acgtagcgaa attcgcagga agtaaggtca 40

<210>115

<211>47

<212>DNA

<213> Artificial sequence

<220>

<223> O113 medium probe

<400>115

cacactcatt acgtgttcaa aagtgatgca atcatcaact tcacact 47

<210>116

<211>44

<212>DNA

<213> Artificial sequence

<220>

<223> O104 upstream primer

<400>116

gcaagccctc acgtagcgaa ggtttgataa atcctgtaaa gagc 44

<210>117

<211>38

<212>DNA

<213> Artificial sequence

<220>

<223> O104 downstream primer

<400>117

gcaagccctc acgtagcgaa cgccctagaa acctgact 38

<210>118

<211>45

<212>DNA

<213> Artificial sequence

<220>

<223> O104 media probe

<400>118

actagcacac tcgcgacaat aaaacctgcg atatctgctt tgacc 45

<210>119

<211>40

<212>DNA

<213> Artificial sequence

<220>

<223> O45 upstream primer

<400>119

gcaagccctc acgtagcgaa tacgatttca caagcttcca 40

<210>120

<211>41

<212>DNA

<213> Artificial sequence

<220>

<223> O45 downstream primer

<400>120

gcaagccctc acgtagcgaa agccactgaa tattgcacat t 41

<210>121

<211>37

<212>DNA

<213> Artificial sequence

<220>

<223> O45 medium sub-probe

<400>121

tgacgtcgta ccgcgatccc aagatcgggc attagct 37

<210>122

<211>40

<212>DNA

<213> Artificial sequence

<220>

<223> O142 upstream primer

<400>122

gcaagccctc acgtagcgaa tccagtcttg atagcgatgt 40

<210>123

<211>38

<212>DNA

<213> Artificial sequence

<220>

<223> O142 downstream primer

<400>123

gcaagccctc acgtagcgaa taagcctccc gtcaactc 38

<210>124

<211>43

<212>DNA

<213> Artificial sequence

<220>

<223> O142 media probe

<400>124

cctgcagtgt ggcactatgg gtaaatttgc tgtaataacc cca 43

Claims

1. A probe set comprising a detection probe and at least two mediator probes, wherein,

2. The panel of claim 1, wherein the panel has one or more characteristics selected from the group consisting of:

(1) the set of probes comprises at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, at least 10, at least 12, at least 15, or at least 20 mediator probes; for example, the set of probes comprises 2, 3, 4, 5, 6, 7, 8, 9, 10 or more mediator probes; preferably, the media probe or target-specific sequence comprised by it targets specific nucleic acid sequences of 2, 3, 4, 5, 6, 7, 8, 9, 10 or more bacterial serotypes;

(2) all the medium sub-probes comprise different medium sub-sequences; and, all mediator probes contain target-specific sequences that are different from each other;

(3) all mediator probes each target a different target nucleic acid sequence; preferably, the different target nucleic acid sequences are each specific for the same or different bacterial serotypes;

(4) at least one mediator probe or a target-specific sequence targeting control sequence comprised by it; preferably, the control sequence is a bacteria-specific sequence, such as an e.coli gene sequence;

(5) each bacterial serotype is independently selected from Escherichia coli O serotype, Escherichia coli H serotype, Escherichia coli K serotype, Salmonella O serotype, Salmonella H serotype, Vibrio parahaemolyticus O serotype, Vibrio parahaemolyticus K serotype, Shigella O serotype, Vibrio cholerae O serotype; preferably, each bacterial serotype is independently selected from the group consisting of Escherichia coli O29, Escherichia coli O29, Escherichia coli O26, Escherichia coli O169, Escherichia coli O161, Escherichia coli O126, Escherichia coli O8, Escherichia coli O143, Escherichia coli O1, Escherichia coli O157, Escherichia coli O148, Escherichia coli O27, Escherichia coli O167, Escherichia coli O6, Escherichia coli Gp6, Escherichia coli O15, Escherichia coli O159, Escherichia coli Gp12, Escherichia coli O25, Escherichia coli O166, Escherichia coli O91, Escherichia coli Gp2, Escherichia coli O86, Escherichia coli O111, Escherichia coli O121, Escherichia coli O145, Escherichia coli O55, Escherichia coli Gp9, Escherichia coli O63, Escherichia coli O18, Escherichia coli O128, Escherichia coli O119, Escherichia coli O153, Escherichia coli O103, Escherichia coli O29, Escherichia coli, Escherichia coli O113, Escherichia coli O104, Escherichia coli O45, Escherichia coli O142, Escherichia coli O5, Escherichia coli O7, Salmonella O1, Salmonella O5, Vibrio cholerae O1, Vibrio cholerae O139, Vibrio parahaemolyticus O1, Vibrio parahaemolyticus O3, Listeria O1, Listeria O4, or any combination thereof;

(6) the set of probes further comprises an upstream oligonucleotide sequence; preferably, for each target nucleic acid sequence and mediator probe, an upstream oligonucleotide sequence is provided comprising a sequence complementary to the target nucleic acid sequence; and, when hybridized to the target nucleic acid sequence, the upstream oligonucleotide sequence is upstream of the target-specific sequence of the mediator probe;

(7) the set of probes further comprises a downstream oligonucleotide sequence; preferably, for each target nucleic acid sequence and mediator probe, a downstream oligonucleotide sequence is provided comprising a sequence complementary to the target nucleic acid sequence; and, when hybridized to the target nucleic acid sequence, the downstream oligonucleotide sequence is located downstream of the target-specific sequence of the mediator probe;

preferably, the set of probes comprises the upstream and downstream oligonucleotide sequences and the 5' ends of the upstream and downstream oligonucleotide sequences comprise an identical oligonucleotide sequence; more preferably, the probe set further comprises a universal primer having a sequence complementary to the same oligonucleotide sequence.

3. The panel of claim 1 or 2, wherein the media probe has one or more characteristics selected from the group consisting of:

(1) each of said mediator probes independently comprises or consists of a naturally occurring nucleotide, a modified nucleotide, a non-natural nucleotide, or any combination thereof;

(2) the length of the mediator probe is 15-150nt, such as 15-20nt, 20-30nt, 30-40nt, 40-50nt, 50-60nt, 60-70nt, 70-80nt, 80-90nt, 90-100nt, 100-;

(3) the length of the target specific sequence in the mediator probe is 10-140nt, such as 10-20nt, 20-30nt, 30-40nt, 40-50nt, 50-60nt, 60-70nt, 70-80nt, 80-90nt, 90-100nt, 100-140 nt, 110-120nt, 120-130nt, 130-140 nt;

(4) the length of the mediator sequence in the mediator probe is 5-140nt, such as 5-10nt, 10-20nt, 20-30nt, 30-40nt, 40-50nt, 50-60nt, 60-70nt, 70-80nt, 80-90nt, 90-100nt, 100-110nt, 110-120nt, 120-130nt, 130-140 nt; and

(5) each of said mediator probes independently has a 3'-OH terminus, or its 3' -terminus is blocked;

and/or the presence of a gas in the gas,

the detection probe has one or more characteristics selected from the group consisting of:

(1) the detection probe comprises or alternatively consists of a naturally occurring nucleotide, a modified nucleotide, a non-natural nucleotide, or any combination thereof;

(2) the length of the detection probe is 15-1000nt, such as 15-20nt, 20-30nt, 30-40nt, 40-50nt, 50-60nt, 60-70nt, 70-80nt, 80-90nt, 90-100nt, 100-200nt, 200-300nt, 300-400nt, 400-500nt, 500-600nt, 600-700nt, 700-800nt, 800-900nt, 900-1000 nt;

(3) the length of each capture sequence in the detection probe is 10-500nt, such as 10-20nt, 20-30nt, 30-40nt, 40-50nt, 50-60nt, 60-70nt, 70-80nt, 80-90nt, 90-100nt, 100-150nt, 150-200nt, 200-250nt, 250-300nt, 300-350nt, 350-400nt, 400-450nt, 450-500 nt;

(4) the length of the template sequence in the detection probe is 1-900nt, such as 1-5nt, 5-10nt, 10-20nt, 20-30nt, 30-40nt, 40-50nt, 50-60nt, 60-70nt, 70-80nt, 80-90nt, 90-100nt, 100-200nt, 200-300nt, 300-400nt, 400-500nt, 500-600nt, 600-700nt, 700-800nt, 800-900 nt;

(5) the detection probe has a 3'-OH terminus, or its 3' -terminus is blocked;

(6) the detection probe is a self-quenching probe; for example, the detection probe is labeled with a reporter group at its 5 'end or upstream and a quencher group at its 3' end or downstream, or is labeled with a reporter group at its 3 'end or downstream and a quencher group at its 5' end or upstream; preferably, the reporter and quencher are separated by a distance of 10-80nt or more;

(7) the reporter group in the detection probe is a fluorophore group (e.g., ALEX-350, FAM, VIC, TET, CAL)

Gold 540, JOE, HEX, CAL Fluor Orange 560, TAMRA, CAL Fluor Red 590, ROX, CAL Fluor Red 610, TEXAS Red, CAL Fluor Red 635, Quasar 670, CY3, CY5, CY5.5, Quasar 705); and, the quenching group is a molecule or group capable of absorbing/quenching the fluorescence (e.g., DABCYL, BHQ (e.g., BHQ-1 or BHQ-2), ECLIPSE, and/or TAMRA);

(8) the detection probe is resistant to nuclease activity (e.g., 5' nuclease activity, e.g., 5' to 3' exonuclease activity); for example, the backbone of the detection probe comprises modifications that are resistant to nuclease activity, such as phosphorothioate linkages, alkylphosphotriester linkages, arylphosphotriester linkages, alkylphosphonate linkages, arylphosphonate linkages, hydrogenphosphate linkages, alkylaminophosphate linkages, arylaminophosphate linkages, 2' -O-aminopropyl modifications, 2' -O-alkyl modifications, 2' -O-allyl modifications, 2' -O-butyl modifications, and 1- (4' -thio-PD-ribofuranosyl) modifications;

(9) the detection probe is linear or has a hairpin structure; and

(10) the detection probe comprises a plurality of capture sequences; and, the plurality of capture sequences are arranged in an adjacent manner, in a spaced-apart manner with a linker sequence, or in an overlapping manner.

4. The panel of claim 2, wherein said upstream oligonucleotide sequence has one or more characteristics selected from the group consisting of:

(1) the upstream oligonucleotide sequences each independently comprise or consist of naturally occurring nucleotides, modified nucleotides, non-natural nucleotides, or any combination thereof;

(2) the length of the upstream oligonucleotide sequence is 15-150nt, such as 15-20nt, 20-30nt, 30-40nt, 40-50nt, 50-60nt, 60-70nt, 70-80nt, 80-90nt, 90-100nt, 100-;

(3) the upstream oligonucleotide sequences are each independently located at the upstream distal end of the mediator probe, or located adjacent to the upstream of the mediator probe, or have a partially overlapping sequence with the target-specific sequence of the mediator probe after hybridization with the target nucleic acid sequence; and

(4) the upstream oligonucleotide sequences are each independently a primer specific for the target nucleic acid sequence or a probe specific for the target nucleic acid sequence;

and/or the presence of a gas in the gas,

the downstream oligonucleotide sequence has one or more characteristics selected from the group consisting of:

(1) the downstream oligonucleotide sequences each independently comprise or consist of naturally occurring nucleotides, modified nucleotides, non-natural nucleotides, or any combination thereof; and

(2) the length of the downstream oligonucleotide sequence is 15-150nt, such as 15-20nt, 20-30nt, 30-40nt, 40-50nt, 50-60nt, 60-70nt, 70-80nt, 80-90nt, 90-100nt, 100-;

and/or the presence of a gas in the gas,

the universal primer has one or more characteristics selected from the group consisting of:

(1) the universal primer comprises or alternatively consists of a naturally occurring nucleotide, a modified nucleotide, a non-natural nucleotide, or any combination thereof; and

(2) the length of the universal primer is 8-50nt, such as 8-15nt, 15-20nt, 20-30nt, 30-40nt, or 40-50 nt.

5. The panel of claim 1, wherein the panel has one or more characteristics selected from the group consisting of:

(1) the set of probes comprises detection probes selected from the group consisting of: a detection probe shown as SEQ ID NO. 2, a detection probe shown as SEQ ID NO. 18, a detection probe shown as SEQ ID NO. 31, a detection probe shown as SEQ ID NO. 44, a detection probe shown as SEQ ID NO. 60, a detection probe shown as SEQ ID NO. 70, a detection probe shown as SEQ ID NO. 80, a detection probe shown as SEQ ID NO. 99, a detection probe shown as SEQ ID NO. 112, or any combination thereof;

(2) the probe set comprises a mediator probe selected from the group consisting of: the mediator probe shown in SEQ ID NO. 5, the mediator probe shown in SEQ ID NO. 8, the mediator probe shown in SEQ ID NO. 11, the mediator probe shown in SEQ ID NO. 14, the mediator probe shown in SEQ ID NO. 17, the mediator probe shown in SEQ ID NO. 21, the mediator probe shown in SEQ ID NO. 24, the mediator probe shown in SEQ ID NO. 27, the mediator probe shown in SEQ ID NO. 30, the mediator probe shown in SEQ ID NO. 34, the mediator probe shown in SEQ ID NO. 37, the mediator probe shown in SEQ ID NO. 40, the mediator probe shown in SEQ ID NO. 43, the mediator probe shown in SEQ ID NO. 47, the mediator probe shown in SEQ ID NO. 50, the mediator probe shown in SEQ ID NO. 53, the mediator probe shown in SEQ ID NO. 56, the mediator probe shown in SEQ ID NO. 59, the mediator probe shown in SEQ ID NO. 63, the mediator probe shown in SEQ ID NO. 66, the mediator probe shown in SEQ ID NO. 69, the mediator probe shown in SEQ ID NO. 73, the mediator probe shown in SEQ ID NO. 76, the mediator probe shown in SEQ ID NO. 79, the mediator probe shown in SEQ ID NO. 83, the mediator probe shown in SEQ ID NO. 86, the mediator probe shown in SEQ ID NO. 89, the mediator probe shown in SEQ ID NO. 92, the mediator probe shown in SEQ ID NO. 95, the mediator probe shown in SEQ ID NO. 98, the mediator probe shown in SEQ ID NO. 102, 105 as shown in SEQ ID NO, 108 as shown in SEQ ID NO, 111 as shown in SEQ ID NO, 115 as shown in SEQ ID NO, 118 as shown in SEQ ID NO, 121 as shown in SEQ ID NO, 124 as shown in SEQ ID NO, or any combination thereof;

(3) the set of probes further comprises an upstream oligonucleotide selected from the group consisting of: the upstream oligonucleotide shown as SEQ ID NO. 3, the upstream oligonucleotide shown as SEQ ID NO. 6, the upstream oligonucleotide shown as SEQ ID NO. 9, the upstream oligonucleotide shown as SEQ ID NO. 12, the upstream oligonucleotide shown as SEQ ID NO. 15, the upstream oligonucleotide shown as SEQ ID NO. 19, the upstream oligonucleotide shown as SEQ ID NO. 22, the upstream oligonucleotide shown as SEQ ID NO. 25, the upstream oligonucleotide shown as SEQ ID NO. 28, the upstream oligonucleotide shown as SEQ ID NO. 32, the upstream oligonucleotide shown as SEQ ID NO. 35, the upstream oligonucleotide shown as SEQ ID NO. 38, the upstream oligonucleotide shown as SEQ ID NO. 41, the upstream oligonucleotide shown as SEQ ID NO. 45, the upstream oligonucleotide shown as SEQ ID NO. 48, the upstream oligonucleotide shown as SEQ ID NO. 51, the upstream oligonucleotide shown as SEQ ID NO. 54, the upstream oligonucleotide shown as SEQ ID NO. 57, the upstream oligonucleotide shown as SEQ ID NO. 61, the upstream oligonucleotide shown as SEQ ID NO. 64, the upstream oligonucleotide shown as SEQ ID NO. 67, the upstream oligonucleotide shown as SEQ ID NO. 71, the upstream oligonucleotide shown as SEQ ID NO. 74, the upstream oligonucleotide shown as SEQ ID NO. 77, the upstream oligonucleotide shown as SEQ ID NO. 81, the upstream oligonucleotide shown as SEQ ID NO. 84, the upstream oligonucleotide shown as SEQ ID NO. 87, the upstream oligonucleotide shown as SEQ ID NO. 90, the upstream oligonucleotide shown as SEQ ID NO. 93, the upstream oligonucleotide shown as SEQ ID NO. 96, 100, 103, 106, 109, 113, 116, 119, 122, or any combination thereof;

(4) the set of probes further comprises a downstream oligonucleotide selected from the group consisting of: the downstream oligonucleotide shown as SEQ ID NO. 4, the downstream oligonucleotide shown as SEQ ID NO. 7, the downstream oligonucleotide shown as SEQ ID NO. 10, the downstream oligonucleotide shown as SEQ ID NO. 13, the downstream oligonucleotide shown as SEQ ID NO. 16, the downstream oligonucleotide shown as SEQ ID NO. 20, the downstream oligonucleotide shown as SEQ ID NO. 23, the downstream oligonucleotide shown as SEQ ID NO. 26, the downstream oligonucleotide shown as SEQ ID NO. 29, the downstream oligonucleotide shown as SEQ ID NO. 33, the downstream oligonucleotide shown as SEQ ID NO. 36, the downstream oligonucleotide shown as SEQ ID NO. 39, the downstream oligonucleotide shown as SEQ ID NO. 42, the downstream oligonucleotide shown as SEQ ID NO. 46, the downstream oligonucleotide shown as SEQ ID NO. 49, the downstream oligonucleotide shown as SEQ ID NO. 52, the downstream oligonucleotide shown as SEQ ID NO. 55, the downstream oligonucleotide shown as SEQ ID NO. 58, the downstream oligonucleotide shown as SEQ ID NO. 62, the downstream oligonucleotide shown as SEQ ID NO. 65, the downstream oligonucleotide shown as SEQ ID NO. 68, the downstream oligonucleotide shown as SEQ ID NO. 72, the downstream oligonucleotide shown as SEQ ID NO. 75, the downstream oligonucleotide shown as SEQ ID NO. 78, the downstream oligonucleotide shown as SEQ ID NO. 82, the downstream oligonucleotide shown as SEQ ID NO. 85, the downstream oligonucleotide shown as SEQ ID NO. 88, the downstream oligonucleotide shown as SEQ ID NO. 91, the downstream oligonucleotide shown as SEQ ID NO. 94, the downstream oligonucleotide shown as SEQ ID NO. 97, 101, 104, 107, 110, 114, 117, 120, 123, or any combination thereof; and

(5) the probe set also comprises a universal primer shown as SEQ ID NO. 1.

6. The panel of claim 1, wherein said panel is a panel selected from the group consisting of:

(1) the first probe group comprises a detection probe shown as SEQ ID NO. 2 and 5 medium sub-probes shown as SEQ ID NO. 5, 8, 11, 14 and 17 respectively. Preferably, the first set of probes further comprises: 3, 6, 9, 12 and 15, respectively, as shown in SEQ ID NO. More preferably, the first set of probes further comprises: 5 downstream oligonucleotides as shown in SEQ ID Nos. 4, 7, 10, 13 and 16, respectively, a universal primer as shown in SEQ ID No. 1, or any combination thereof;

(2) and a second probe group, which comprises a detection probe shown as SEQ ID NO. 18 and 4 medium sub-probes shown as SEQ ID NO. 21, 24, 27 and 30 respectively. Preferably, the second set of probes further comprises: 4 upstream oligonucleotides as shown in SEQ ID NO 19, 22, 25 and 28, respectively. More preferably, the second set of probes further comprises: 4 downstream oligonucleotides as shown in SEQ ID NO:20, 23, 26 and 29, respectively, a universal primer as shown in SEQ ID NO:1, or any combination thereof;

(3) and the third probe group comprises a detection probe shown as SEQ ID NO. 31 and 4 medium sub-probes shown as SEQ ID NO. 34, 37, 40 and 43 respectively. Preferably, the third set of probes further comprises: 4 upstream oligonucleotides as shown in SEQ ID NO 32, 35, 38 and 41, respectively. More preferably, the third set of probes further comprises: 4 downstream oligonucleotides as shown in SEQ ID NO. 33, 36, 39 and 42, respectively, a universal primer as shown in SEQ ID NO. 1, or any combination thereof;

(4) a fourth probe set comprising the detection probe shown as SEQ ID NO. 44 and 5 mediator probes shown as SEQ ID NO. 47, 50, 53, 56 and 59, respectively. Preferably, the fourth set of probes further comprises: 45, 48, 51, 54 and 57 of the 5 upstream oligonucleotides. More preferably, the fourth set of probes further comprises: 46, 49, 52, 55 and 58, respectively, as shown in SEQ ID NO, 1, or any combination thereof;

(5) a fifth probe set comprising the detection probe shown in SEQ ID NO:60 and 3 mediator probes shown in SEQ ID NO:63, 66 and 69, respectively. Preferably, the fifth set of probes further comprises: 3 upstream oligonucleotides shown as SEQ ID NO 61, 64 and 67, respectively. More preferably, the fifth set of probes further comprises: (ii) 3 downstream oligonucleotides as shown in SEQ ID NOs 62, 65 and 68, respectively, a universal primer as shown in SEQ ID No. 1, or any combination thereof;

(6) a sixth probe set comprising the detection probe shown in SEQ ID NO. 70 and 3 mediator probes shown in SEQ ID NO. 73, 76 and 79, respectively. Preferably, the sixth set of probes further comprises: 71, 74 and 77, respectively. More preferably, the sixth set of probes further comprises: (ii) 3 downstream oligonucleotides as shown in SEQ ID NOs 72, 75 and 78, respectively, a universal primer as shown in SEQ ID No. 1, or any combination thereof;

(7) and the seventh probe group comprises a detection probe shown as SEQ ID NO. 80 and 6 medium sub-probes shown as SEQ ID NO. 83, 86, 89, 92, 95 and 98 respectively. Preferably, the seventh set of probes further comprises: and 6 upstream oligonucleotides shown as SEQ ID NOS 81, 84, 87, 90, 93 and 96 respectively. More preferably, the seventh probe set further comprises: 82, 85, 88, 91, 94 and 97, respectively, as shown in SEQ ID NO, 1, or any combination thereof.

(8) An eighth probe set comprising the detection probe shown as SEQ ID NO. 99 and 4 mediator probes shown as SEQ ID NO. 102, 105, 108 and 111, respectively. Preferably, the eighth set of probes further comprises: and 4 upstream oligonucleotides shown in SEQ ID NO 100, 103, 106 and 109. More preferably, the eighth set of probes further comprises: 4 downstream oligonucleotides as shown in SEQ ID NO 101, 104, 107 and 110, respectively, a universal primer as shown in SEQ ID NO 1, or any combination thereof.

(9) A ninth probe set comprising the detection probe shown in SEQ ID NO:112 and 4 mediator probes shown in SEQ ID NO:115, 118, 121 and 124, respectively. Preferably, the ninth set of probes further comprises: 113, 116, 119 and 122, respectively. More preferably, the ninth probe set further comprises: 4 downstream oligonucleotides as shown in SEQ ID NO:114, 117, 120 and 123, respectively, a universal primer as shown in SEQ ID NO:1, or any combination thereof.

7. A kit comprising one or more sets of probes as defined in any one of claims 1 to 6; optionally, the kit further comprises: an enzyme having 5' nuclease activity, a nucleic acid polymerase, or any combination thereof;

preferably, the kit comprises at least 1, at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, at least 10 probe sets;

preferably, the kit comprises one or more of the first to ninth probe sets, for example 1, 2, 3, 4, 5, 6, 7, 8 or 9.

8. A kit, comprising: m detection probes and n mediator sub-probes, wherein n is an integer of 2 or more (e.g., n is an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40 or more), m is an integer less than n and greater than 0, and,

each detection probe is independently labeled with a reporter group and a quencher group, wherein the reporter group can emit a signal, and the quencher group can absorb or quench the signal emitted by the reporter group; and, each detection probe emits a signal when hybridized to its complement that is different from the signal when not hybridized to its complement;

preferably, the kit has one or more characteristics selected from the group consisting of:

(1) the kit comprises at least 1, at least 2, at least 3, at least 4, at least 5, at least 6, at least 8, at least 10 detection probes;

(2) the kit comprises at least 2, at least 3, at least 4, at least 5, at least 6, at least 8, at least 10, at least 15, at least 20, at least 25, at least 30, at least 35, at least 40, at least 45 mediator probes;

(3) the kit further comprises an upstream oligonucleotide; preferably, the upstream oligonucleotide is as defined in any one of claims 2 to 6;

(4) the kit further comprises a downstream oligonucleotide; preferably, the downstream oligonucleotide is as defined in any one of claims 2 to 6;

(5) the kit further comprises a universal primer; preferably, the universal primer is as defined in any one of claims 2 to 4;

(6) the detection probe is as defined in any one of claims 2 to 6;

(7) the media probe as defined in any one of claims 2 to 6; and

(8) the kit further comprises: an enzyme having 5' nuclease activity, a nucleic acid polymerase, or any combination thereof.

9. The kit of claim 7 or 8, having one or more characteristics selected from the group consisting of:

(1) the mediator sequences of all mediator probes in the kit target different target nucleic acid sequences respectively;

(2) all the mediator probes in the kit comprise different mediator sequences;

(3) all mediator probes in the kit comprise target-specific sequences that are different from each other;

(4) all detection probes in the kit are respectively and independently labeled with the same or different reporter groups;

(5) the kit further comprises: a reagent for performing nucleic acid hybridization, a reagent for performing mediator probe cleavage, a reagent for performing nucleic acid extension, a reagent for performing nucleic acid amplification, a reagent for performing reverse transcription, or any combination thereof; and

(6) the enzyme having 5' nuclease activity is a nucleic acid polymerase (e.g., a DNA polymerase, particularly a thermostable DNA polymerase) having 5' nuclease activity (e.g., 5' exonuclease activity); preferably, the DNA polymerase is obtained from a bacterium selected from the group consisting of: thermus aquaticus (Taq), Thermus thermophiles (Tth), Thermus filiformis, Thermus flavus, Thermococcus literalis, Thermus antalidanii, Thermus caldophlus, Thermus cholephilus, Thermus flavus, Thermus igilterrae, Thermus lacteus, Thermus oshima, Thermus ruber, Thermus rubens, Thermus scodottus, Thermus silvannus, Thermus thermophilus, Thermotoga maritima, Thermotoga poliana, Thermosipho africans, Thermococcus littoralis, Thermococcus pilosus, Thermococcus maculatus, Thermococcus purpurea, Thermomyces solitarius, Thermomyces barosis, Thermococcus purpurea, Thermomyces purpurea, Thermosophilus, Thermomyces littoralis, Thermococcus purpurea, Pyrococcus purpurea, Pyrococcus purpurea; particularly preferably, the DNA polymerase is Taq polymerase.

10. Use of a set of probes according to any one of claims 1 to 6 for the preparation of a kit for detecting the presence or level of a bacterial serotype in a sample or for diagnosing whether a subject is infected with said bacterial serotype;

preferably, the sample comprises DNA, or RNA, or a mixture of nucleic acids;

preferably, the target nucleic acid sequence is DNA or RNA; and/or, the target nucleic acid sequence is single-stranded or double-stranded;

preferably, the sample is a sample obtained from a subject, e.g., feces, anal swab, bacterial culture, etc.; preferably, the subject is a mammal, e.g., a primate, e.g., a human;

preferably, the bacterial serotype is selected from the group consisting of escherichia coli O serotype, escherichia coli H serotype, escherichia coli K serotype, salmonella O serotype, salmonella H serotype, vibrio parahaemolyticus O serotype, vibrio parahaemolyticus K serotype, shigella O serotype, vibrio cholerae O serotype; preferably, the bacterial serotype is selected from the group consisting of Escherichia coli O29, Escherichia coli O29, Escherichia coli O26, Escherichia coli O169, Escherichia coli O161, Escherichia coli O126, Escherichia coli O8, Escherichia coli O143, Escherichia coli O1, Escherichia coli O157, Escherichia coli O148, Escherichia coli O27, Escherichia coli O167, Escherichia coli O6, Escherichia coli Gp6, Escherichia coli O15, Escherichia coli O159, Escherichia coli Gp12, Escherichia coli O25, Escherichia coli O166, Escherichia coli O91, Escherichia coli Gp2, Escherichia coli O86, Escherichia coli O111, Escherichia coli O121, Escherichia coli O145, Escherichia coli O55, Escherichia coli Gp9, Escherichia coli O63, Escherichia coli O18, Escherichia coli O128, Escherichia coli O119, Escherichia coli O153, Escherichia coli O103, Escherichia coli O113, Escherichia coli type O104, Escherichia coli type O45, Escherichia coli type O142, Escherichia coli type O5, Escherichia coli type O7, Salmonella type O1, Salmonella type O5, Vibrio cholerae type O1, Vibrio cholerae type O139, Vibrio parahaemolyticus type O1, Vibrio parahaemolyticus type O3, Listeria monocytogenes type O1, Listeria monocytogenes type O4, or any combination thereof.