[Detection of mutations in codon 306 of the embB gene for molecular genetic characterization of clinical Mycobacterium tuberculosis strains].

A total of 254 Mycobacterium tuberculosis strains were used in the study. Among them, there were 183 ethambutol (EMB)-resistant strains, 13 multidrug resistant ones, but EMB-sensitive, and 39 strains sensitive to rifampicin (RIF), isoniazid (INZ), and EMB. All the strains were analyzed for genetic changes in three loci: embB306, rpoB, and katG/inhA promoter, which were associated with the formation of resistance to EMB, RIF, and INZ, respectively. The Mycobacterium tuberculosis strains were obtained from pulmonary tuberculosis patients living in the Central Region of the Russian Federation. Resistance to RIF, INZ, and EMB was revealed by the absolute concentration test. The inhibitory concentration (IC) of EMB was determined for all the strains. Genetic changes in the above loci were estimated by mini-sequencing, followed by mass-spectrometry recording MALDI-TOF products. The relative low frequency of embB306 mutations was observed among the EMB-resistant strains (about 41.5%). Mutations in codon 306 were detected only in strains with EMB IC > or = 2 mg/L. A statistical significant association was found between the frequency of embB306 mutations and the multidrug resistant phenotype. A combination of these mutations with the traditional genetic markers of multidrug resistance may be used for the more effective detection of multidrug-resistant strains.