CIRCULATION OF MULTIDRUG-RESISTANT TUBERCULOSIS PATHOGEN STRAINS IN THE REPUBLIC OF KARELIA
One hundred and sixteen drug-resistant (DR) Mycobacterium tuberculosis (MBT) strains and 127 multidrug-resistant (MDR) MBT ones isolated from first detected patients with tuberculosis were studied. Molecular genetic methods were used to study 119 strains (54 MDR, 40 DR, and 25 polyresistant (PR) strains. Among the MDR strains, the high <i>in vitro</i> growth rate and intensity was seen 10 times more frequently than those among the strains with preserved drug resistance. The absolute majority (90.9%) of MDR strains and half the PR strains, which circulated in the Republic of Karelia, belonged to the genetic family Beijing. Rifampicin resistance in most MDR strains from the Beijing family was associated with the 531 TCG→TTG mutation of the <i>rpo</i>B gene, which determined a high resistance to rifampicin and a cross-resistance to rifabutins. The presented data demonstrate the epidemic hazard of MDR strains of the Beijing genotype, which circulate in Karelia.