Objectives We aimed to characterise patterns of anal and oral detection of Treponema pallidum among men who have sex with men (MSM) with early syphilis.
Methods 200 MSM with serologically confirmed primary, secondary and early latent syphilis were tested with T. pallidum polA PCR using an anal canal swab, oral rinse, plus swabs from any anal and oral lesions in a prospective, cross-sectional study. Anal and oral T. pallidum cycle threshold values were compared between subsets of men and according to rapid plasma reagin (RPR) titre.
Results Of 200 men with early syphilis, 45 and 48 had anal and oral T. pallidum detected, respectively. Cycle threshold values were lower with anal compared with oral T. pallidum whether lesions were present or not. Among 27 and 42 men with anal and oral T. pallidum detected, respectively, and no anal or oral primary lesion, frequency of detection increased with increasing RPR titre, with 95% (25/27) and 98% (41/42) of shedding from respective sites occurring with RPR titres ≥1:16. 6.5% (13/200) of men with syphilis had concurrent detection of T. pallidum from both anal and oral sites: 9/13 with secondary syphilis, 7/9 of whom had anal lesions with a median duration of 30 days (range 7–180 days).
Conclusions These data suggest T. pallidum load at the anus is higher than at the oral cavity and that a subset of men with secondary syphilis and prolonged anal lesions may be relatively infectious. Earlier detection and treatment of syphilis, when RPR titres are lower than 1:16, could potentially reduce infectiousness from anal and oral sites.
Data availability statement
Data are available on reasonable request.
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Handling editor Jo Gibbs
Twitter @EricPFChow, @drdebwilliamson
Contributors JMT and MYC conceived the idea for this study. Study visits were done by RW or JMT. JMT analysed the data. JMT and MYC drafted the manuscript. EPFC and LZ provided advice on statistical analysis. DW oversaw the laboratory work, FA assisted with laboratory testing and methodology, CKF reviewed the statistical output, and SG contributed to the interpretation of microbiological data. All authors critically reviewed the manuscript for important intellectual content and approved the final version. JMT and RW had access to and verified the underlying study data. JMT is responsible for the overall content as the guarantor.
Funding This work was supported by an Australian National Health and Medical Research Council (NHMRC) Partnership Project Grant (APP 2003399). JMT is supported by a Monash University Post-Doctoral Bridging Grant. DW and EPFC are supported by an NHMRC Emerging Leadership Investigator Grant (GNT 1174555 for DW and GNT 1172873 for EPFC). CKF is supported by an Australian NHMRC Leadership Investigator Grant (GNT1172900).
Competing interests MYC and DW have received donated materials from SpeeDx and Hologic.
Provenance and peer review Not commissioned; externally peer reviewed.
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