Detection of Treponema pallidum by Semi-Nested PCR in the Cerebrospinal Fluid of Asymptomatic HIV-Infected Patients with Latent Syphilis

Background: Neurosyphilis diagnosis is frequently dependent upon the results of serological tests and cerebrospinal fluid abnormalities, but the reliability of findings in patients with HIV-1 infection has been questioned, especially in asymptomatic patients with latent syphilis. In this study, we present the data on the presence of T. pallidum DNA in CSF from asymptomatic HIV-infected patients with the diagnosis of syphilis. Methods: CSF and serum samples were collected from 12 HIV-infected patients attending a tertiary care clinic located in southern Brazil, during the period 2012 to 2013. Results: In CSF samples from five of 12 patients (40%), we detected T. pallidum DNA. Unexpectedly, in these patients, the CSF cell count, protein and glucose levels were normal. In addition, none of these 5 CSF samples presented a positive VDRL reaction. Serum VDRL titers were similar between patients with positive and negative CSF T. pallidum DNA. Most patients with detectable T. pallidum DNA presented low serum VDRL titers. A higher serum VDRL titer of 1:64 was observed in only one patient. Conclusions: Our results have shown that asymptomatic HIV-infected patients with evidence of latent syphilis and normal CSF might present detectable T. pallidum DNA in the CSF. The detection of T. pallidum DNA by our semi-nested PCR provides additional information beyond conventional CSF analysis for the diagnosis of neurosyphilis. The detection of T. pallidum DNA in CSF despite normal CSF findings in HIV-infected patients could also provide a different therapeutic approach including the use of intravenous aqueous crystalline penicillin.