Detection Of Treponemal Tp47 And Tp0548 Genes In Lesion Swabs From Syphilis Patients

Background Typical syphilis ulceration (chancre) can appear at the site of sexual contact during primary syphilis, and this lesion can be swabbed for detection of Treponema pallidum DNA. Two well-known gene targets for syphilis detection are tp47 and pol A with sensitivities between 60–70%. The use of T. pallidum PCR in primary and secondary syphilis diagnosis and confirmation are recommended in European and CDC guidelines respectively. We evaluated tp47 and tp0548 as molecular screening targets; either target, if present, would indicate the presence of T. pallidum in the sample. Methods Participants with syphilis clinical diagnosis were enrolled in a cohort study in Peru in 2019 and 2020. All participants were clinically examined to determine the presence of lesions. Lesion exudate was collected with a dacron swab and stored in a vial with 500ul of lysis buffer. T. pallidum DNA was extracted and tested using specific primers in conventional polymerase chain reaction (PCR) to amplify tp47 and tp0548 target genes. Results Overall, 61/162 participants presented with lesions, and 27 (43.5%) of them had T. pallidum DNA detected by either tp47 or tp0548 targets. The frequency of finding both targets in the same sample was 15/27 (55.6%). Only 1 sample was positive for tp47 but negative for tp0548, while 34 samples were negative for both T. pallidum targets. Additionally, only tp0548 was detected in 11 samples. We found tp47 in 16/61 (26.2%) samples and tp0548 in 26/61 (42.6%) samples. Adding the tp0548 screening target, increased the detection of T. pallidum by 69%. Conclusion tp0548 may help as a screening target to increase the detection of T. pallidum in lesions. Thus both markers are necessary to increase sensitivity of detection T. pallidum DNA in lesions.