Genetic structure and drug resistance of <i>Mycobacterium tuberculosis</i> strains in the Kemerovo Region — Kuzbass

Abstract

Background. Kemerovo Region has a high burden of tuberculosis (TB) with incidence rates twice the national average. The circulating variants of Mycobacterium tuberculosis significantly influence the TB epidemic process. Screening of epidemically significant variants of the pathogen in areas with a high burden of TB underlies epidemiological diagnosis and is necessary for the development of effective prevention measures. However, the population structure of M. tuberculosis in the Kemerovo Region — Kuzbass is poorly understood.
 Aims: to study genetic heterogeneity and phenotypic resistance to anti-tuberculosis drugs of M. tuberculosis strains in the Kemerovo Region.
 Materials and methods. The MIRU-VNTR genotyping of 163 M. tuberculosis strains isolated from TB patients in the Kemerovo Region in March–October 2022 was carried out. Cultivation of M. tuberculosis, drug susceptibility testing, and isolation of genomic DNA were carried out by standard methods. Genotypic identification was performed using MIRU-VNTR (24 loci) typing. In parallel, express genotyping was carried out: identification of isolates of the Beijing genotype (by RD105/207) and non-Beijing; subtyping Beijing using real-time PCR tests for detection of Central Asian Russian and B0/W148; identification of the non-Beijing group by real-tine PCR RT tests for LAM, S, Ural.
 Results. The isolates of the Beijing genotype (67.5%) were found to dominate both among newly diagnosed (64.4%) and previously treated patients (88.5%). MIRU-VNTR typing revealed 75 profiles, of which 94-32 (35.3%) and 100-32 (15.7%) were the most abundant and belonged to the Beijing genotype. Overall, 39.9% and 20.9% of isolates, respectively, were assigned to the Beijing Central Asian Russian and B0/W148 epidemic clusters, which differed significantly in MDR levels (50.8% and 85.3%, respectively; p = 0.005). The second most common were strains of the genetic family of the Euro-American lineage (L4) (31.9%): LAM (6.7%) Ural (7.4%) Haarlem (4.9%) and L4-unclassified (12.9%), MDR among of these minor genotypes was significantly lower than among Beijing genotype strains, and amounted to 11.5% (p 0.001). Strains from HIV-TB patients (56.4% of the total sample) carried an MDR profile more often (54.8%) compared to TB cases without HIV infection (35.2%) (p = 0.005), which may be due to higher proportion of Beijing genotype strains in the HIV-TB group (75.0% vs. 57.7%; p = 0.026). Complete comparability of the SNP analysis (in-house tests) to identify the main genotypes and epidemically significant Beijing subtypes was shown, which made it possible to characterize 75.5% of the sample by the express method.
 Conclusions. The molecular genetic screening carried out in the Kemerovo Region revealed the heterogeneity of the M. tuberculosis population, which was dominated by strains of the Beijing genotype, with the frequency of subtypes comparable with other territories of the Siberian Federal District.