P57

Multidrug resistant tuberculosis (MDR-TB) constitutes a major health problem in Russia and globally. Certain Mycobacterium tuberculosis genotypes are more clinically/epidemiologically significant due to the higher transmissibility and association with MDR. The aim of this study was to perform molecular characterization of the recent collection of M. tuberculosis MDR strains from newly-diagnosed TB patients in Northwest Russia. We studied 497 M. tuberculosis strains isolated in 2017-2019. The Beijing genotype and its main subtypes B0/W148, Central Asian/Russian and CAO (Central Asian Outbreak) were determined by PCR of specific markers and 24 MIRU-VNTR typing (followed by comparison with MIRU-VNTRplus.org). Non-Beijing isolates were spoligotyped and compared to the SITVIT2 database. MDR was detected in 35.2% (175) of strains and was caused mainly by mutations rpoB Ser450Leu and katG Ser315Thr. Among MDR strains, Beijing genotype strains prevailed (84.6%; 148/175): modern Beijing (n=142) and ancient/ancestral Beijing (n=6, all type 1071-32). Beijing B0/W148 strains (44.6%; 66/148) were predominantly represented by type 100-32 (74.2%; 49/66). Central Asian/Russian genotype strains (48.0%; 71/148) were more heterogeneous by VNTR loci than B0/W148 strains (HGI 0.74 vs HGI 0.45). The Central Asian/Russian strains were represented by the following clusters: 94-32 (33/71; 46.5%), 1065-32 (17/71; 23.9%), 95-32 (6/71; 8.5%). Eleven strains belonged the CAO genotype. Non-Beijing strains (15.4%; 27/175) were represented by the families LAM, Ural, T, Haarlem. Thus, the increase in the proportion of primary MDR-TB in Northwest Russia is due to the continued active transmission of M. tuberculosis Beijing strains, mainly those of genotype B0/W148.

Acknowledgements: Russian Science Foundation (grant 19-14-00013).