Molecular Detection and Typing of in Non-Ocular Samples from Patients with Ocular Syphilis.

Introduction: Ocular syphilis is a rare but potentially sight-threatening manifestation of infection with the spirochete subspecies . Molecular strain typing of clinical specimens obtained from patients with syphilis can provide useful epidemiological and clinical information. In this study, we assess the utility of non-ocular clinical samples in strain typing for patients with diagnosed ocular syphilis.

Methods: We collected samples of excess blood, serum, and cerebrospinal fluid (CSF) from 6 patients with ocular syphilis treated in 2013-2016. DNA was extracted, purified, and then analyzed using an enhanced molecular typing method including sequence analysis of , number of repeats in the gene, and restriction fragment length polymorphism of the gene.

Results: Molecular strain typing based on gene sequence analysis revealed two cases of type F and two cases of type G in 3 of 6 (50%) cases with CSF samples, 1 of which was obtained after starting antibiotics. In a patient with 2 distinct episodes, the same type (type G) was identified in both episodes using different sample types (CSF, whole blood). Serum samples were available in 6 cases, but none were successfully typed with any of the methods. Amplification of the and genes was unsuccessful in all cases. Overall, strain types were identified in 4 of the 7 episodes.

Conclusion: strain types F and G were detected in CSF or whole blood in 4 of 7 episodes in this series. We demonstrate moderate sensitivity of strain typing in ocular syphilis using non-ocular clinical specimens.