Evaluation of a PCR Test for Detection of Treponema pallidum in Swabs and Blood

Abstract

Syphilis diagnosis is based on clinical observation, serological analysis, and dark-field microscopy (DFM) detection of Treponema pallidum subsp. pallidum, the etiological agent of syphilis, in skin ulcers. We performed a nested PCR (nPCR) assay specifically amplifying the tpp47 gene of T. pallidum from swab and blood specimens. We studied a cohort of 294 patients with suspected syphilis and 35 healthy volunteers. Eighty-seven of the 294 patients had primary syphilis, 103 had secondary syphilis, 40 had latent syphilis, and 64 were found not to have syphilis. The T. pallidum nPCR results for swab specimens were highly concordant with syphilis diagnosis, with a sensitivity of 82% and a specificity of 95%. Reasonable agreement was observed between the results obtained with the nPCR and DFM methods (kappa ‫؍‬ 0.53). No agreement was found between the nPCR detection of T. pallidum in blood and the diagnosis of syphilis, with sensitivities of 29, 18, 14.7, and 24% and specificities of 96, 92, 93, and 97% for peripheral blood mononuclear cell (PBMC), plasma, serum, and whole-blood fractions, respectively. HIV status did not affect the frequency of T. pallidum detection in any of the specimens tested. Swab specimens from mucosal or skin lesions seemed to be more useful than blood for the efficient detection of the T. pallidum genome and, thus, for the diagnosis of syphilis.

2014 European guideline on the management of syphilis

“…Materiałem do badań mogą być tkanki, płyn mó-zgowordzeniowy (PMR), krew (metoda o niskiej czułości) itp. [14][15][16][17][18][19][20]. Nie istnieje na świecie jedna platforma PCR zaakceptowana do diagnostyki kiły, dlatego należy używać tylko metod poddanych dokładnej walidacji i z zastosowaniem odpowiedniej kontroli jakości.…”

The Endemic Treponematoses

“…An additional limitation of molecular testing for the treponematoses is that the sensitivity of DNA detection in a biological sample varies by the type of sample analyzed (e.g., lesion exudates versus blood samples) and, likely, the fluctuations in the bacterial burden in the host that accompany these multistage diseases (211). Furthermore, only a limited number of yaws and bejel strains has been analyzed using these methods, and no definitive proof of the stability of these signatures among subspecies is currently available.…”

“…Examples of molecular tests include the amplification of the tmpA (TP0768) and the 4D genes (also known as tpf-1 [TP1038]), used by Hay et al (201,207) or the amplification of the bmp gene (TP1016) used by Noordhoek et al (202). The use of qualitative or quantitative PCR targeting the 47-kDa lipoprotein (TP0574) gene was also evaluated to diagnose syphilis (199,203,(208)(209)(210)(211)(212)(213). Since the early 2000s, the T. pallidum subsp.…”

Multiplex nested polymerase chain reaction for Treponema pallidum using blood is more sensitive than using serum

“…The sensitivity and specificity of the molecular PCR test results are affected by the type of specimen, the PCR method, and the target gene used. (10,11) Specimens that may be used for the Treponema pallidum PCR test in secondary syphilis are exudates from syphilitic lesions and blood. The sensitivity of PCR with smears from lesions of secondary syphilis reaches 80% and the specificity 98.6%.…”