Frequency of Treponema pallidum invasion into cerebrospinal fluid in primary or secondary early-stage syphilis.

Frequency of Treponema pallidum invasion into cerebrospinal fluid (CSF) has not been clear at this present. Since it is impossible to culture T. pallidum in vitro at this present, we need molecular based-approach to detect it in CSF. Additionally, neurosyphilis is usually a late sequela, however it might result in asymptomatic neurosyphilis even at primary or secondary syphilis. This study was to reveal the frequency of T. pallidum invasion into CSF especially at primary or secondary syphilis with polymerase chain reaction (PCR) test. All patients were visited the Aichi Medical University Hospital or Izumi ladies' clinic between 2016 and 2017. Clinical CSF samples were collected from patients with early and late stages of syphilis. The PCR was done using primers targeting the tpN47gene. CSF samples were collected from 9 patients (4 patients with primary syphilis, 3 with secondary syphilis, and 1 early latent syphilis and 1 with late latent syphilis). PCR showed positive reaction in 2 of 7 (28.6%) primary and secondary syphilis patients, in 1 of 1 (100%) early latent syphilis patients, and in 1 of 1 (100%) late latent syphilis patients. Despite its lack of sensitivity for use alone as a diagnostic test, this PCR test should be preferred for the diagnosis of neurosyphilis. Because, T. pallidum was detected in the 28.6% CSF of patients at primary and secondary syphilis, which indicated that they invade the central nervous system from the early stages of infection. However, studies in a larger population are required to confirm these preliminary results.