[Evaluation of biochips for the rifampin resistance detection of M. tuberculosis in strains isolated at the Novosibirsk and Tomsk regions].

Recently in Russia biochips for rifampin resistance detection of M. tuberculosis were developed. To investigate the conformity between rifampin resistance results determined both by the routinely used absolute concentration method and USING the biochips, 272 DNA samples of M. tuberculosis isolated from TB patients at Novosibirsk and Tomsk regions in 2000-2005 were analyzed. The biochip can detect 30 mutations in rpoB gene. The mutations were also tested using the single stranded conformational polymorphism method (SSCP). In addition, 60 DNAs were randomly sampled and sequenced. The results of rifampin resistance detection using biochip and absolute concentration methods were congruent in 86% cases, and were different when analyzed samples consisted of the susceptible and resistant strains of M. tuberculosis mixture. The most frequent mutations in the rpoB gene were S531 (76.2%), H526 (7%), D516 (5.6%), and L511 (5.6%). In 94% of rifampin resistant strains, there was also resistance to isoniazid. Therefore, in Siberia the rifampin resistance is the reliable marker for MDR strains of M. tuberculosis, and biochips can be used also for their detection. To hybridize with biochip the fluorescent-labeled single-stranded DNAs were routinely synthesized by two PCR, and intermediary product after the first PCR should be transferred into another tube. The last stage included high risk of cross-contamination. To exclude the risk, primer concentrations and temperature-time profile of PCR reactions were improved, and both PCR were combined in one tube. The two methods were congruent in 100%. The one tube method would be especially attractive for the routine PCR laboratory.

[Evaluation of reasons of the MDR M. tuberculosis strains dissemination by analysis of the rifampicin and/or isoniazid resistant isolates].

During the last years in Novosibirsk region of Russia the rate of TB patients infected by MDR strains of M. tuberculosis has been constantly increasing. This increase may occur as a result of the spontaneously mutated mycobacterium selection during treatment of patients or as a result of primary infection by the resistant M. tuberculosis, or also, as a result of both reasons in combination. If the main reason of MDR strain dissemination is selection of resistant bacterium during patient treatment, the equal apportionment of the dominated mutation into the mycobacterium genotypes would be observed. If the main reason is the primary infection by resistant M. tuberculosis, the unequal apportionment would be revealed. For deeper understanding of the main reasons of the fast MDR strains spreading in the region, the distribution of the main mutations over genotypes of strains in Novosibirsk (170 isolates) and Tomsk prison (51 isolates) was investigated. Mutations in rpoB gene associated with the rifampicin resistance and in katG (isoniazid resistance) were detected by biochips. M. tuberculosis genotypings were carried out by IS6110 PCR typing or MIRU typing, in the last method the twelve loci (MIRU 2, 4, 10, 16, 20, 23, 24, 26, 27, 31, 39, 40) have been used. The most frequent mutation in the rpoB gene was Ser531-->Leu (60-70% of the rifampicin resistant strains) and Ser315-->Thr in gene katG (80% of the isoniazid resistant M. tuberculosis). Both in Novosibirsk and in Tomsk prison the rates of clustered cases transmissions were high (69 and 63% respectively). Analysis of the distribution of the dominated mutations Ser531-->Leu (rpoB) and Ser315-->Thr (katG) revealed that all of them were detected in each clusters, but in Novosibirsk there were only two clusters, in which the percentage of strains, containing mutation Ser531-->Leu (rpoB) were higher (85.7% and 77.7% respectively, P < 0.05), then in others. Among the Tomsk prison's clusters it was revealed one in which the proportion of the Ser3 15-->Thr mutation in katGwas higher (96.4%, P < 0.05). The nonuniform distribution of the dominated mutations highlighted that the epidemic spread of drug-resistant strains of M. tuberculosis in region resulted from the selection of them during patient treatment and the subsequent transmission by TB patients.

[Molecular and genetic characterization of rifampicin- and/or izoniazid-resistent strains of M. tuberculosis, isolated in Novosibirsk and Tomsk regions].

The purpose of the work was to study rifampicin- and izoniazid-resistent strains of M. tuberculosis, circulating in Western Siberia, by VNTR and IS6110 typing. The authors also studied genetic causes of resistance to these antibiotics and undertook a search of new VNTR loci, displaying polymorphism in genomes of closely related clonally-disseminated variants of Mycobacterium tuberculosis in W-Beijing family model analysis.

[Genetic polymorphism of clinical Mycobacterium tuberculosis strains circulating in the territory of Novosibirsk Region].

Mycobacterium tuberculosis strains isolated from patients treated at TB dispensary branches in different districts of Novosibirsk were studied by genetic analysis. The below molecular methods were used: 1. PCR with random primers; 2. A method based on variable number of tandem repeats in loci; 3. IS6110 inverse PCR. Thirty-five samples of genome DNA of M. tuberculosis isolated were analyzed. Each of the 3 methods detected the main group of isolates, which comprised 61.8% of closely related strains revealed by method 1, 75.8%--by method 2, and 74.3%--by method 3. The remaining clusters were represented by 1 to 4 strains. The data obtained denote a relative homogeneity of M. tuberculosis strains circulating in Novosibirsk Region. No interplay was detected between the clustering of isolates and the presence or absence of mutation in genes conditioning the resistance to antibiotics.