Genetic antimicrobial resistance determinants and their prevalence in molecular subtypes of Treponema pallidum subsp. pallidum

Abstract

Objective. To investigate genetic determinants of resistance to antimicrobial agents recommended for the treatment of syphilis and assess their prevalence in molecular subtypes of Treponema pallidum subsp. pallidum in the Russian Federation over the period of 2014-2017. Materials and Methods. A total of 161 clinical isolates of T. pallidum obtained from Tyva, Stavropol, Irkutsk, Kaluga, Novosibirsk and Omsk regions were included in this study. Genetic material of T. pallidum was detected by PCR with primers to polA gene. Determinants of resistance to penicillins (tromp1, tp47), tetracyclines (16S rRNA) and macrolides (23S rRNA) were determined using the gene sequence analysis. Molecular typing was performed by characterizing variable arp, tpr (E, G, J) and tp0548 genes according to the CDC protocol. Results of this study were compared to historical data on antimicrobial resistance of T. pallidum over the period of 2011-2012. Results. Analysis of tromp1 and tp47 gene sequences detected C22G and G208T substitutions, respectively. These polymorphisms were not significant for activity of the corresponding proteins, but differed the studied clinical isolates from the reference strain Nichols, therefore, linking them with epidemic genogroup T. pallidum Street Strain 14. Based on the analysis of G1058C mutation in the 16S rRNA gene, all clinical isolates obtained in 2014-2017 belonged to wild type, whereas this genetic determinant of resistance to tetracyclines was determined in 2 of 190 isolates obtained in 2011-2012. Also, A2059G/C mutation in the 23S rRNA gene was not found, whereas a significant A2058G substitution in this gene was determined in 4 isolates obtained in 2014-2017. Results of this study confirm sporadic resistance to macrolides in the Russian Federation, which was previously (2011-2012) found in 3 of 190 isolates of T. pallidum. A2058G mutation was detected predominantly in minor subtypes of T. pallidum (14 b/f, 14 b/g and 14 d/g) and was unrepresentative for molecular subtype 14 d/f which is a predominant one in the Russian Federation. Conclusions. The long-term use of penicillins for the treatment of syphilis did not result in emergence of T. pallidum resistance to this antibiotic class. An absence of genetic determinants of resistance to tetracyclines confirms them to be second-line drugs. A sporadic prevalence of determinants of resistance to macrolides requires they be used for the treatment of syphilis with caution.

Prevalence of the A2058G mutation in 23S rRNA gene, which determines Treponema pallidum macrolide resistance in Russian population

“…Россия относится к географическим регионам с низ кой распространенностью устойчивости к макролидам [17,18]. Как уже указывалось, наиболее распростра ненный генотип T. pallidum на территории России -14d/f, и в интервале 2014-2021 гг.…”

“…Нуклеотидная за мена A2058G типична для субтипов 14b/f, 14b/g, 14d/g, получивших широкое распространение в США и странах Европейского союза [9]. На территории России устойчиво доминирует субтип 14d/f [17]. О выделении на территории России устойчивых к азитромицину штам мов T. pallidum сообщалось в 2013 г.: два штамма, вы деленных от больных в республике Тыва, были отнесены к субтипам 14d/g и 14b/f [18].…”