Detection of Treponema pallidum DNA by targeting the tp0574 and tp0548 genes in genital lesion, oral swab, and anal swab samples from a cohort of Peruvian patients with syphilis

Treponema pallidum (T. pallidum) can be detected by molecular techniques. However, research is needed to determine the best specimen and DNA gene target for this molecular detection. Previous research has employed the tp0574 gene as a target in nucleic acid tests for T. pallidum detection, whereas the tp0548 gene has mainly been used for molecular typing of T. pallidum. We evaluated the effectiveness of using tp0574 alone and both targets, tp0574 and tp0548, for T. pallidum detection in anal, oral, and lesion swab samples from syphilis cases. Between 2019 and 2022, participants diagnosed with syphilis in Peru were enrolled. A total of 258 oral, 116 anal, and 87 lesion swab samples were collected and processed to amplify both target genes using qualitative PCR. T. pallidum DNA was detected in 8.5% oral, 38.8% anal, and 49.4% lesion samples. We obtained a significantly higher proportion of positives when both genes were used compared with using tp0574 alone. Detection rates increased from 3.9% using tp0574 only to 8.5% when combining both tp0574 and tp0548 in oral samples (P < 0.05), and detection in lesion samples increased from 24.1 to 49.4% using both targets (P < 0.001). We also observed significant differences when comparing the proportion of participants with T. pallidum DNA detected between those with one and two or three samples collected (P < 0.001). Amplifying tp0574 and tp0548 genes improves the detection of T. pallidum DNA, and collecting samples from multiple anatomical sites (anal and oral samples) could facilitate syphilis diagnosis when lesions are not observed. IMPORTANCE Treponema pallidum DNA amplification may be a useful technique to aid in the diagnosis of syphilis and increase case infection. While specific genes have been used in PCR techniques for this purpose, the tp0574 gene has been used as a main target due to its specificity; the best single or combination of gene targets is unknown. Given the tp0548 gene is employed for genotyping, only a few studies have evaluated its utility for T. pallidum detection. Here, we have evaluated two gene targets (tp0574 and tp0548) for T. pallidum DNA detection in extragenital and lesion samples from persons with syphilis. We found that the implementation of tp0548 as a second target improves T. pallidum DNA detection and that tp0548 alone performs better than tp0574 in both oral and lesion samples. However, further research is necessary to explore the implementation of tp0548 target to improve the detection in diverse types of samples.