48. TREPONEMA PALLIDUM PCR: APPLICATION AND DIAGNOSTIC VALUE IN 2 CASES OF PRIMARY SYPHILIS

Abstract

Epidemics of infectious syphilis have been ongoing in large cities in industrialised countries since the turn of the millennium. These epidemics have almost exclusively involved homosexually active men, with a disproportionately high rate among HIV infected individuals. Genital ulcerative disease, including syphilis, has a strong correlation with onward transmission of viral and bacterial sexually transmitted infections.

Due to the lack of a culture system for Treponema pallidum, the causative organism of syphilis, other direct test methods are needed in the evaluation of skin lesions possibly due to syphilis. Dark ground microscopy was once commonly used by sexual health clinicians, but skills in this method have waned in recent years. Polymerase chain reaction (PCR) assays are being increasingly used in the diagnosis of infectious syphilis.

We describe the use of a nucleic acid amplification assay for Treponema pallidum, which targets the 47 kilodalton gene, in the diagnosis of primary syphilis in 2 patients with genital lesions. The first patient was an HIV infected man who presented with an ulcer typical of a chancre but who denied any recent risk behaviour. The second was an HIV negative homosexually active man with an atypical genital lesion. In both cases, Treponema pallidum PCR was positive and serology was consistent with the diagnosis of primary syphilis.

Conclusion/Recommendation: Appropriately validated Treponema pallidum nucleic acid amplification assays could replace dark ground microscopy and direct fluorescent antigen tests as a direct test for early infectious syphilis. It could be particularly useful in individuals who have treponemal skin lesions of atypical appearance.