Characteristics of polymerase chain reaction–positive syphilis cases in Manitoba, Canada, 2017 to 2020: Demographic analysis, specimen types, and Treponema pallidum gene targets

Abstract

BACKGROUND: A resurgence of syphilis infections has been described in a number of countries including Canada in the last decade. METHODS: This study identified polymerase chain reaction (PCR) positive syphilis cases based on detection of Treponema pallidum genes ( polA, tpp47, and bmp) in 3,350 clinical specimens obtained from patients in the province of Manitoba, Canada between 2017 and 2020. Patient demographics were obtained from specimen requisition forms. RESULTS: PCR identified 740 syphilis cases: 718 were adolescents and adults, while 22 were congenital syphilis cases. For non-congenital syphilis investigation, the clinical specimens with the highest yield of positive PCR results were genital (632), oral (73), and anal (55), while for congenital syphilis, they were nasal or nasopharyngeal secretions (20), followed by blood (5) and umbilical cord (4). Female syphilis cases appeared younger (61.7% between 14 and 29 years), while male syphilis cases appeared older (58.4% between 30 and 65 years). Although, overall more syphilis cases (62.7%) occurred in the urban cities; the proportion of urban cases showed a significant decline from 87.0% in 2017 to 55.6% in 2020, while in rural regions it increased from 13.0% in 2017 to 44.4% in 2020. Most (98.8%) PCR- positive specimens were found to contain all three T. pallidum genes and 99.8% also displayed the macrolide resistance genotype. CONCLUSIONS: This study identified the clinical specimen types and T. pallidum genes most suitable for PCR diagnosis of syphilis. Changing demographics of cases were noted over time.