A New Specimen for Syphilis Diagnosis: Evidence by High Loads of Treponema pallidum DNA in Saliva

Background. DNA from many pathogens can be detected in saliva. However, the presence and quantity of Treponema pallidum DNA in patients with syphilis in saliva is unknown. Methods. 234 patients with syphilis with different stages and 30 volunteers were enrolled. Paired saliva and plasma samples were collected from all participants. Consecutive saliva samples from 9 patients were collected every 4 hours following treatment. Treponema pallidum DNA in samples was determined by nested polymerase chain reaction (PCR) and droplet digital PCR targeting polA and Tpp47. Results. Treponema pallidum DNA detection rates in saliva and plasma were 31.0% (9/29) and 51.7% (15/29) in primary syphilis (P=.11), 87.5% (63/72) and 61.1% (44/72) in secondary syphilis (P<.001), 25.6% (21/82) and 8.5% (7/82) in latent syphilis (P=.004), and 21.6% (11/51) and 5.9% (3/51) in symptomatic neurosyphilis (P=.021), respectively. Median (range) loads of Tpp47 and polA in saliva were 627 (0-101 200) and 726 (0-117 260) copies/mL, respectively, for patients with syphilis. In plasma, however, loads of Tpp47 and polA were low: medians (range) of 0 (0-149.6) and 0 (0-176) copies/mL, respectively. Loads of T. pallidum DNA in saliva during treatment fluctuated downward; the clearance time was positively correlated with the loads of T. pallidum DNA before treatment. Conclusions. Collection of saliva is noninvasive and convenient. The high loads of T. pallidum DNA in saliva and reduction after treatment indicated that saliva can be not only a diagnostic fluid for syphilis but also an indicator of therapeutic effectiveness.

Automated summary

The study revealed significant differences in the detection rate and quantity of Treponema pallidum DNA in saliva among patients with different stages of syphilis. The load of T. pallidum DNA in saliva decreases after treatment, indicating its potential as an indicator of therapeutic effectiveness.