MOLECULAR EPIDEMIOLOGY OF TUBERCULOSIS IN THE KALININGRAD REGION OF RUSSIA: 10 YEARS AFTER

Abstract

In the Kaliningrad region, the incidence of tuberculosis (TB) has declined significantly over the past decade (from 134/100 000 in 2006 to 50.6/100 000 in 2015), but still exceeds the average for the North-West Russia (40.7/100 000). In view of the increase in the proportion of primary multidrug resistance (MDR) of the causative agent from 23.9% in 2010 to 30.5% in 2015, the aim of this study was to analyze the current Mycobacterium tuberculosis population structure in the Kaliningrad region and to evaluate its spatial-temporal trends. The 73 M. tuberculosis isolates from patients with pulmonary TB newly diagnosed in 2015 were studied. Drug resistance (DR) was detected in 46 (63.0%) M. tuberculosis strains; of these, 32 (43.8%) were multidrug-resistant (MDR). The 46 (63.0%) of 73 M. tuberculosis strains were of the Beijing genotype with 19.2% (14 out of 73) share of the B0/W148 cluster. Spoligotyping of 27 non-Beijing M. tuberculosis strains made it possible to identify 15 spoligotypes of 5 genetic families — T, LAM, Ural, S, X. About half (16; 51.6%) of non-Beijing strains were represented by spoligotypes — SIT42, SIT53, SIT262, and SIT444. In a heterogeneous group T, mostly drugsusceptible strains of spoligotype SIT53 were prevailing. More than half (55.6%) of the LAM genotype strains exhibited DR. The Ural family was small (5.5%) and included strains of well-known in Russia M. tuberculosis spoligotypes SIT35 and SIT262, and one new, not found previously. MDR was statistically significantly associated with the Beijing genotype: 56.5% versus 25.9% in strains of other genotypes (in total) (P = 0.0134). Moreover, all 14 strains of epidemiologically and clinically significant B0/W148 cluster were MDR. The proportion of MDR strains of the Beijing genotype did not change significantly: in 2006 it was 61.3%, in 2015 — 56.5% (P = 0.6773). However, the spectrum of drug resistance to first-line anti-TB drugs expanded. If previously the majority (78.9%) of MDR strains additionally exhibited resistance to streptomycin only, in present study 72.0% of MDR strains were resistant to streptomycin, ethambutol, and pyrazinamide. The proportion of MDR strains of non-Beijing genotypes was 25.9%, a significantly higher than the similar indicators in 2006 — 2.2% (P = 0.0124). A relatively smaller proportion of strains of the Beijing genotype (50%) was found in TB patients from the shores of the Baltic Sea, a territory with a relatively more favorable socio-economic situation and a higher standard of living. Thus, the current epidemiological situation of TB in the Kaliningrad region is crucially determined by the growing circulation of MDR Beijing family strains, as well as a significant increase in the proportion of MDR strains of other genotypes.