Direct Detection of Treponema Pallidum in Diagnosisof Syphilis

Overview

Available methods for direct diagnosis of syphilis are summarized with emphasis being on thosepromising for routine use.Direct detection of the causative agent T. pallidum is limited since the agent is not able to synthesizeenzyme cofactors, fatty acids and nucleotides de novo, is completely dependent on its host and thusculture on synthetic media is not feasible. Direct diagnosis of syphilis is based on rabbit infectivitytesting (RIT), dark field or fluorescent microscopyandrecently also onmolecular biological methodsused with increasing frequency in routine practice. Suitability and usability of different methodsfor direct detection of T. pallidum at different stages of syphilis are explained. Except for molecularbiological methods, most of detection techniques can only be used at the primary and secondarystages or in early congenital syphilis.Major PCR methods for diagnosis of syphilis are presented. Not all of them are suitable for use inroutine practice owing to differences in their sensitivity and design. The polA PCR method appearsto be the most promising in this regard.

Key words:
syphilis – Treponema pallidum – direct detection – polA PCR.