BACKGROUND
In the Murmansk region, the first molecular genetic studies of circulating strains of Mycobacterium tuberculosis were carried out during the years of an increase in the incidence of tuberculosis (TB) (2003—2006). The study’s aim was the genotypic characterization of the M. tuberculosis population in the Murmansk region and the analysis of changes in its structure over fifteen years.
MATERIAL AND METHODS
The 67 M. tuberculosis strains from patients with TB newly diagnosed in 2017 were studied. The strains were assigned to the Beijing genotype and its major clusters based on analysis of specific markers. The Beijing strains were typed by 24 MIRU-VNTR loci. All non-Beijing strains were subjected to spoligotyping.
RESULTS
The genotypes of M. tuberculosis were identified: Beijing (52.2%), Ural (19.4%), T (9.0%), LAM (7.5%), Haarlem (3.0%) and X (1.5%). Among Beijing strains, the cluster Central-Asian/Russian with heterogeneous MIRU-VNTR profiles was predominant — 34.3% (23/67). Multiple drug resistance (MDR) — resistance to rifampicin and isoniazid caused by mutations rpoB Ser531Leu (TCG → TTG) and katG Ser315Thr (AGC → ACC) was detected in 26.9% of the strains; the largest proportion of MDR strains was found in the Beijing B0/W148 cluster (85.7%), represented mainly by the MIRU-VNTR profile 100-32. High levels of clustering of Beijing Central-Asian Russian (CR=0.68) and B0/W148 (CR=0.71) strains reflect their current dissemination.
CONCLUSIONS
In 2003—2017 a steady dominance of the Beijing genotype with a tendency to an increase from 44.0% to 52.2% was observed. The proportion of MDR strains in the cluster B0/W148 Beijing increased 3.5 folds, thus indicating the selection and accumulation of this epidemiologically and clinically unfavorable variant of the tuberculosis pathogen in Murmansk region.