Determination of molecular types and resistance to macrolides in Treponema pallidum isolates isolated in the Russian Federation

Background. The number of syphilis cases in the Russian Federation increased significantly in 2022. Control of heterogeneity of Treponema pallidum subtypes is important to monitor the emergence and spread of antibiotic-resistant strains Aims. To determine molecular subtypes and resistance to macrolides in T. pallidum isolates isolated in the Russian Federation in 2022. Methods. We analyzed DNA isolated from 49 samples of clinical material obtained from patients from dermatovenerological treatment and prevention facilities in three federal districts (CFD, SFD, SCFD) of the Russian Federation in 2022 with diagnoses of primary syphilis and secondary syphilis. T. pallidum DNA isolation and confirmation of the presence of genetic material were performed according to the existing algorithms. To search for genetic determinants of resistance to macrolides, a fragment of the 23S rRNA gene was analyzed. Primary decoding of nucleotide sequences was performed in Sequencing Analysis 5.3.1. Mega 11 program was used to align the analyzed fragments of target genes to T. pallidum reference sequences. Results. In 2022, three subtypes of T. pallidum were identified in the territory of the represented federal districts of the Russian Federation: 14d/f, 14d/g, 14d/d with continued dominance of subtype 14d/f. The macrolide-resistant subtype 14d/d was identified in two federal districts, which is new for the Russian Federation. Conclusions. The population of T. pallidum continues to expand in the Russian Federation, including the emergence of azithromycin-resistant strains. The data obtained confirm the need for continuous monitoring of circulating strains and may facilitate understanding of their geographic distribution.