Transborder molecular analysis of drug-resistant tuberculosis in Mongolia and Eastern Siberia, Russia.

Eastern Siberia (Russia) and Mongolia are borderline regions in Asia with a high incidence of tuberculosis (TB). In this study, we investigated the transborder transmission of Mycobacterium tuberculosis with a focus on endemic and epidemic clones and drug resistance. M. tuberculosis isolates (287 from Mongolia and 754 from Russia) were collected using cross-sectional population-based surveys between 2010 and 2016. The isolates were genotyped using 24 variable number of tandem repeat loci and by testing of the key markers to discriminate within the Beijing genotype. All isolates were divided into 427 mycobacterial interspersed repetitive units types that were assigned to Lineage 2 (Beijing) and Lineage 4 (Ural, Haarlem, Latin American-Mediterranean [LAM], S, unclassified). The Beijing genotype was dominant in both countries (69% in Russia, 75% in Mongolia). However, the Beijing isolates differed significantly between the countries, in terms of the identified subtypes. LAM was the most common non-Beijing genotype (11.1% in Mongolia and 14.9% in Russia) and LAM isolates mostly belonged to the LAM-RUS branch in both countries. The multidrug-resistance (MDR) rate was higher in Russia than in Mongolia among newly diagnosed patients: 29.4% versus 5.6% (p < .001). In Mongolia, the MDR rate was similar in Beijing (29.7%) and non-Beijing (27.5%) genotypes. In Russia, a higher MDR rate was observed in (i) Beijing compared with non-Beijing (48.7% versus 38.3%, p = .03) and (ii) Beijing B0/W148 compared with Beijing Central Asian/Russian (63.4% versus 37.3%, p < .001). In conclusion, the M. tuberculosis population structure in Mongolia was shaped by mainly historical interaction with China (dominance of the Beijing genotype) and Northern Eurasia (presence of the LAM-RUS branch). In contrast, the transborder transmission of M. tuberculosis since the 1990s between Mongolia and its neighbours has been negligible, and the adverse trends of MDR-TB in Russia did not impact the current situation in Mongolia.