Background Cali is a syphilis-endemic area, with a very high prevalence of gestational syphilis (14.7/1000 live births) and congenital syphilis (7.7/1000 live births). Molecular typing techniques are useful for studying bacterial strain diversity, molecular epidemiologic patterns and antimicrobial resistance patterns. The study objective was to determine the T. pallidum (Tp) strain diversity and analyse for the mutations associated with macrolide-resistance in this syphilis-endemic region.
Methods 19 secondary syphilis (SS) patients, 15 (RPR+, FTA-ABS+, HIV-) and 4 (RPR+, FTA-ABS+, HIV+) were enrolled in the study. Tp DNA was extracted from syphilis skin lesions and quantified by real-time-qPCR targeting polA gene. Molecular typing was performed using established typing and subtyping methods (arp, tpr, tp0279, tp0548) and strains were analysed for A2058G and A2059G mutations within the 23S rRNA gene. Strain diversity in Cali strains (arp and tpr) was compared with other published Tp molecular studies using the Shannon index.
Results 14/19 SS patients were polA PCR positive (range 5.4 – 38.920; mean 3.227 copies/ug total DNA). Among 8/14 samples that were fully typed, 7 strain subtypes (21a11/d, 12d9/f, 10p9/f, 14j10f, 5p9/f, 14k9/f, 14d9/f) were identified with only 2 strains exhibiting identical patterns (21a11/d). The A2059G mutation was found in 1 specimen from an HIV-negative subject. Cali Tp strain types had a Shannon index of 2.2, higher than all 13 studies in other localities reported in two recent reviews.
Conclusions There is a high T. pallidum strain diversity in Cali, Colombia, probably due to population mobilisation and close proximity to other syphilis-endemic regions (i.e. Buenaventura, Pacific Coast). Contact tracing and cluster identification is difficult to achieve in this setting. Although our sample size was small, the identification of the A2059G mutation suggests that macrolides should be used with caution for syphilis treatment in Cali and close monitoring for macrolide resistant strains should be initiated.
- Molecular epidemiology