O06.4 Detection of Treponema pallidum DNA at various body locations as a proxy for infectiousness

Background Syphilis is highly infectious, but it is unknown whether other anatomical sites than the primary infection site contribute to onward transmission. We aimed to evaluate the presence of Treponema pallidum ssp pallidum (TP) at various body locations of syphilis patients to elucidate transmissibility during various syphilis stages. Methods This study was performed at the Sexually transmitted infections( STI) clinic of the Public Health Services in Amsterdam. Eligible were: men who have sex with men (MSM), 18 years or older with clinical signs or symptoms suggestive of syphilis stage 1 or stage 2, and asymptomatic men with a positive syphilis serology. Besides routine diagnostics, anorectal and oropharyngeal swabs, urine samples, and venous blood samples were tested using an in-house polymerase chain reaction targeting the polA gene of Treponema pallidum (Tp-PCR). Results From 2018 to 2019 we included 293 MSM. Seventy patients had primary syphilis, 73 secondary syphilis, 86 early latent syphilis, 14 late latent syphilis, 23 treated syphilis and 27 had no syphilis. Outside of the primary ulcus, TP-DNA was detected in 35/70 among the primary syphilis patients in at least one site (2/70 blood, 7/70 oro-pharynx, 13/70 ano-rectum and 24/70 urine); in 62/73 secondary syphilis patients in at least one site (15/73 blood, 47/73 oro-pharynx, 37/73 ano-rectum and 26/73 urine); and 29/86 early latent syphilis patients in at least one site (5/86 blood, 21/86 oro-pharynx, 11/86 ano-rectum and 6/86 urine ). No TP-DNA was detected among the late latent syphilis, treated syphilis or in the no syphilis group. Conclusion DNA of T.pallidum was frequently detected in various body locations of MSM with primary or secondary syphilis. This is in agreement with the high transmissibility of syphilis.