(P101) DETECTION OF TREPONEMA PALLIDUM IN GENITAL LESION SWABS AND SEROLOGIC TEST PERFORMANCE: SOUTH AFRICA AND BOTSWANA

Background:
Syphilis, caused by Treponema pallidum subspecies pallidum (TP), has been increasing in incidence globally. Syphilis may present with a broad spectrum of symptoms and signs, but genital chancres (primary syphilis) and condylomata lata (secondary syphilis) are common clinical presentations.

Methods:
As part of an ongoing study to characterize genomes of TP in sub-Saharan Africa, we are enrolling patients with genital lesions suspicious of syphilis from public healthcare facilities in Gaborone (Botswana) and East London (South Africa). We collected lesion swabs for TP DNA detection by real-time PCR. Syphilis rapid diagnostic testing (RDT) was performed with DetermineTM Syphilis TP (Abbott®) in South Africa and Standard Q Syphilis Ab Test (SD Biosensor) in Botswana. Treponemal serology was performed with the Alinity i Syphilis TP assay (Abbott GmbH) in South Africa and ARCHITECT Syphilis TP assay (Abbott GmbH) in Botswana.

Results:
From October 2023 to March 2024, 61 participants (35 female and 26 male) were recruited in South Africa. TP PCR was positive in 22/45 (51%) genital ulcer swabs and in 11/16 (69%) condylomata lata swabs. Of those with TP PCR positive genital ulcer swabs, 13/22 (59%) were reactive by RDT and 22/22 (100%) by TP serology. Of those with TP PCR positive condylomata lata swabs, 7/11 (64%) were reactive by RDT and 10/11 (91%) by TP serology. From January 2024 to March 2024, 23 participants (17 female and 6 male) with genital ulcer were recruited in Botswana. All tested TP PCR negative. Of those participants, 3/23 (13%) were reactive by RDT and 2/23 (9%) by TP serology.

Conclusion:
We observed high rates of TP DNA detection in lesion swabs from South Africa and very low rates in Botswana. The syphilis RDT was falsely negative in about 40% of those with TP PCR confirmed genital lesions in South Africa, raising concerns about the syphilis RDT sensitivity.