Background: Treponema pallidum (T. pallidum) prevalence and burden at oral and lesion sites in adults with early syphilis were assessed by qPCR. Factors associated with oral shedding were also examined.
Methods: Pre-treatment oral and lesion swabs were collected from adults with early syphilis in a US multicenter syphilis treatment trial. Oral swabs were collected in the presence and absence of oral lesions. Following DNA extraction, qPCR and whole genome sequencing (WGS) were performed to assess burden and strain variability.
Results: All 32 participants were male, mean age was 35, and 90.6% were living with HIV. T. pallidum oral PCR positivity varied by stage: 16.7% primary, 44.4% secondary, and 62.5% in early latent syphilis. Median oral T. pallidum burden was highest in secondary syphilis at 63.2 copies/µL. Lesion PCR positivity was similar in primary (40.0%) and secondary syphilis (38.5%). Age 18-29 years was significantly associated with oral shedding (vs age 40+) in adjusted models. WGS identified two distinct strains.
Conclusion: T. pallidum DNA was directly detected at oral and lesion sites in a high proportion of men with early syphilis. Younger age was associated with oral shedding. Ease of oral specimen collection and increased PCR availability suggest opportunities to improve syphilis diagnostic testing.
Keywords: Treponema pallidum; early syphilis; lesion swab; oral swab; quantitative PCR (qPCR); shedding; whole genome sequencing (WGS).
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