Diagnóstico, tipagem molecular e avaliação do perfil de resistência de cepas Treponema pallidum

Abstract

Syphilis is a curable sexually transmitted infection that has seen a significant increase in cases in Brazil in recent years, representing a persistent public health problem. Therefore, implementing actions aimed at better access to diagnosis, treatment, and monitoring in primary health care is fundamental to controlling this infectious disease. The development of molecular techniques for the identification of Treponema pallidum subspecies pallidum, the causative agent of syphilis, contributes to an improvement in diagnosis. Furthermore, molecular characterization is an alternative to understanding the transmission of treponemas in Brazil. This research aimed to develop methods for the molecular diagnosis of syphilis through Polymerase Chain Reaction (PCR) and quantitative PCR (qPCR). The positive clinical samples in conventional PCR and qPCR were subjected to molecular characterization of T. pallidum using the Enhanced Centers for Disease Control and Prevention (ECDC) typing method and evaluation of the resistance profile to macrolides and tetracyclines. From June 2018 to December 2022, 23 participants with suspected primary and secondary syphilitic lesions agreed to participate in the study, and 18 participants had clinical samples of the lesions and whole blood collected. Conventional PCR and qPCR molecular techniques were performed. The two clinical samples (lesion and blood) from these 18 participants were tested to detect treponemal DNA. Out of the 36 clinical samples tested, 16 (eight from lesions and eight from blood) had T. pallidum DNA detected by qPCR. Conversely, conventional PCR identified treponemal DNA in 11 clinical samples, eight from lesions and three from blood. The four subtypes of T. pallidum identified by the ECDC method were: 14d/g, 14d/c, 15d/c, and 15d/e. The azithromycin resistance profile was identified in 3 out of 5 (60%) of participants with primary syphilis positive in qPCR. Among these samples, two (66.6%) contained the A2058G mutation, and one sample did not have the mutation. No A2059G mutation was found. There are few studies on the molecular epidemiology of T. pallidum, and even fewer in countries with high rates of syphilis cases, such as the American countries. This reinforces the importance of further studies to identify the molecular profile and resistance in T. pallidum.