Syphilis is a multistage sexually transmitted disease caused by Treponema pallidum ssp. pallidum (TPA). In the recent years, syphilis causes over 7.1 million new cases a year worldwide. Vulnerable populations include men who have sex with men (MSM), sex workers and their clients, transgender people, young adults, migrant populations, and people living in areas with civil conflicts. In the Czech Republic, there are around 700–1000 new syphilis cases annually, with a number of total cases that have increased continuously since 2012. This study analyzed a total of 1,228 samples collected from the years 2004–2022. Of the PCR-positive typeable samples (n = 415), 68.7% were fully-typed, and 31.3% were partially-typed. Most of the identified TPA isolates belonged to the SS14-clade of syphilis strains and only 6.3% were the Nichols-like cluster. Among the fully-typed samples, 33 different allelic profiles were found. Most of the profiles (n = 26) appeared just once in the Czech population, while seven profiles were detected more than twice. The most frequent allelic profiles belonged to two separate groups of SS14-like isolates, including group of 1.3.1 and 1.26.1 profiles, and the second group containing 1.1.8., 1.1.1, and 1.1.3 (representing 57.9%, and 25.3% of all detected allelic profiles, respectively). This work demonstrated a high degree of genetic diversity among TPA isolates collected the Czech Republic and also the dynamic character of TPA allelic profiles in the infected population over the course of almost two decades. In addition, MLST typing of clinical samples from patients diagnosed or suspected of having syphilis suggests the existence of important differences among allelic profiles with respect to the epidemiologic success within the human population.
The work was funded by the National Institute of Virology and Bacteriology (Programme EXCELES, ID Project No. LX22NPO5103, Funded by the European Union - Next Generation EU).