Detection of Treponema pallidum DNA in Oropharyngeal Swabs and Whole Blood for Syphilis Diagnosis.

BACKGROUND

Syphilis diagnosis relies on serological tests, which may be falsely nonreactive or may be reactive but not reflect current syphilis.

METHODS

Polymerase chain reaction for detection of T. pallidum DNA was performed on 123 oropharyngeal swabs, 120 whole bloods, and 46 lesion exudate swabs from 123 untreated individuals with syphilis (cases); oropharyngeal swabs from 148 at-risk controls without syphilis; and 73 oropharyngeal swabs and 36 whole bloods from 73 individuals recently treated for syphilis.

RESULTS

Most (90.2%) cases had early syphilis. T. pallidum DNA was detected in 33 (26.8%) of 123 oropharyngeal swabs, 32 (26.7%) of 120 bloods, and 30 (65.2%) of 46 lesion exudate swabs. T. pallidum DNA was detected in 49 (40.8%) of 120 individuals in whom both oropharyngeal swabs and blood were tested. T. pallidum was more likely to be amplified from oropharyngeal swabs when it was amplified from blood than when it was not (15 of 32 [46.9%] vs. 17 of 88 [19.3%], P = 0.003). For each 2-fold increase in serum rapid plasma reagin titer, the odds of detection of T. pallidum DNA in oropharyngeal swabs increased by 1.44 (95% confidence interval, 1.14-1.82, P = 0.003). T. pallidum DNA was not detected in oropharyngeal samples from controls, but it was detected in 3 (8.3%) of 36 bloods from individuals recently treated for syphilis: 2 at 1 day and 1 at 5 days after initiation of syphilis treatment.

CONCLUSIONS

Nucleic amplification tests can identify recent T. pallidum infection and may be particularly useful for diagnosis of very early or asymptomatic syphilis.