SU1690677A1 - Method for estimation of microorganisms sensitivity to antibiotics - Google Patents

Abstract

This invention relates to medicine, in particular to methods for the rapid determination of the sensitivity of microorganisms to antibiotics. The purpose of the invention is to accelerate the method of determining the sensitivity of microorganisms to antibiotics - achieved by testing samples containing a suspension of microorganisms with different concentrations of antibiotics, incubated for 20-30 minutes, after which they are irradiated with a 30-50 laser for 10-20 seconds. mW and a radiant exposure of 3.107 - 8107 J / m2, at an angle of 7-11? The half-width of the light scattering spectrum is recorded relative to the axis of the exciting beam, and the changes of the half-width of the light scattering spectrum are determined. 2 tabl

Description

The invention relates to medicine, in particular to methods for the rapid determination of the sensitivity of microorganisms to antibiotics, which makes it possible to quickly determine the effective dose of antibiotics for patients with infectious nature of an early, targeted antibiotic therapy.

The purpose of the invention is to accelerate the method for determining the sensitivity of microorganisms to antibiotics.

To achieve the goal, samples containing suspensions of microorganisms with different concentrations of antibiotics are incubated for 20-30 minutes, after which they are irradiated for 10-20 seconds with a continuous radiation laser with a power of 30-50 mW and a radiation exposure of 3-10-107 J / m, at an angle of 7-11 ° relative to the axis of the exciting beam, register the half-width of the scattered light spectrum, determine

changes in the half width of the spectrum of the scattered light by the formula

WITH

with

dg

 Rm - r0

100%,

where T0 and ft are the half-width of the spectrum of scattered light, respectively, before and after incubation, the inhibitory concentration of the antibiotic in the sample is minimally recorded, for which AG is more than 30-90%.

Example 1. To determine the sensitivity of the culture of Staphylococcus aureus (strain N 340) to the antibiotic aminoglycoside neomycin, a series of two-fold dilutions of this antibiotic was prepared in m septone broth, poured into 2 ml tubes. The range of final concentrations of neo-mycin was 0.25 - 128 µg / ml. Suspension culture of staphylococcus was prepared in isotonic sodium chloride solution with OOs.

oh oh oh X

Xi

by 1 billion microbial bodies according to a turbidity standard of 1.0. Then, the microbial suspension was diluted 100 times with the same solution, i.e. to a concentration of bacterial cells up to 10 million / ml.

0.1 ml of culture was introduced into each tube with an antibiotic (500 thousand microbial cells per 1 ml of m sopepton broth). Test tubes with a nutrient medium and an antibiotic in various concentrations (media control) and a test tube with a seeded nutrient medium without an antibiotic (control of culture growth) served as controls. Control and test tubes were placed in a thermostat at 37 ° C and incubated for 20 minutes. Before and after incubation, the tubes were irradiated with an LG-38 helium-neon laser (see Table 1 for parameters). The parameters of the scattered light (Table 1) were recorded using an FEU-79 photomultiplier and a SKA-72 spectrum analyzer with a 50 Hz viewing band. The sensitivity of the device was 4-6%.

After registration and determination of the parameters of the scattered light, the increase in its intensity (A I) in% relative to the initial level, as well as the increase in half width (D Y) in%, are calculated. also relative to the initial level. As a result of 24 experiments, DI for test tubes with a staphylococcal culture with neomycin at a concentration of 0.12 μg / ml was 46.2 ± 5.2%; 0.25 μg / ml-5.02.3%; 0.5 μg / ml2.1 ± 0.3%; 1.0 μg / ml-1.2 ± 0.2% itd.dg, respectively, when the concentration of neomycin was 0.12 μg / ml was 12.33.2%; 0.25 µg / ml-30 4.2%; 0.5 µg / ml-91.0 ± 5.1%; Omkg / ml-96,, 8%, etc. For environmental control tubes and

0

DG was 0%; for test tubes with culture control, respectively, 72.3 ± 0.9. The limit of visible growth in the experiment clearly appeared only after 48 h and was at the level of the neomycin tubes at a concentration of 0.25 μg / ml. Thus, the BMD of neomycin for strain N 340 Staphylococcus aureus was 0.25 µg / ml.

In samples with a DG of 30% and no less, the concentration of the antibiotic was less than IPC, in samples of CDG from 91% or more, the concentration of the antibiotic was more than IPC.

Example 2. Determination of the sensitivity of Staphylococcus aureus (strain No. 5 340) to tetracycline hydrochloride was carried out as described in Example 1.

In samples of cultures with DG less than 30% (7-29.5%), the concentration of tetracycline is less than the IPC, in samples with DG it is more than 90% (91-112%) - higher than the IPC.

Claims (1)

Invention Formula A method for determining microbial sensitivity to antibiotics by incubating a suspension of microorganisms in a liquid nutrient medium with different concentrations of antibiotics, irradiating a continuous radiation laser and recording the scattered light parameter followed by determining the minimum inhibitory concentration, characterized in that, to accelerate the process, incubate the wire t for 20-30 minutes, irradiated with a laser with a power of 30-50 mW and a radiant exposure of 3-U7 - 8-U7 J / m2, at an angle of 7-11 ° relative to the axis of the exciting beam, and calculate the half-width of the spectrum of the scattered light and when its ratio is changed (;), the minimum inhibitory concentration is recorded at 30-90%. T a 6 l and c a 1 0 five 0 five Table 2 Parameter Power of helium-neon laser, mW10.0 Radiant exposure, J / m2 „1.5“ U Time of incubation of cultures with antibiotics4 h IPC antibiotic, µg / ml 0.12 Irradiation time and recording of scattered light parameters 3 min Increase in scattered light intensity 4-U after incubation in culture with IPC of antibiotic 10% Increase in half-width of scattered light spectrum LG after incubation in culture with ibc antibiotic The final microbial concentration cage / l6 10 .The value of the parameters by the method J j prototype proposed 5 °% 8-10 30 min 0.12 20 s 90% 10