Chlamydial ompA Diversity in Trachoma-Hyperendemic Communities Treated With Azithromycin

Abstract

Prior studies have theorized that low chlamydial genetic diversity following mass azithromycin treatments for trachoma may create a population bottleneck that prevents the return of infection, but little empiric evidence exists to support this hypothesis. In this study, a single mass azithromycin distribution was administered to 21 communities in the Gurage Zone of Ethiopia in 2003. All children aged 1–5 years had conjunctival swabs performed before treatment, and at 2 and 6 months following treatment. All swabs positive for Chlamydia trachomatis at 2 months underwent ompA typing, as did the same number of swabs per community from the pre-treatment and 6-month visits. ompA diversity, expressed as the reciprocal of Simpson's index, was calculated for each community. In total, 15 ompA types belonging to the A and B genovars were identified. The mean diversity was 2.11 (95% confidence interval: 1.79, 2.43) before treatment and 2.16 (95% confidence interval: 1.76, 2.55) two months after treatment (P = 0.78, paired t-test). ompA diversity was not associated with the prevalence of ocular chlamydia (P = 0.76), and did not predict subsequent changes in the prevalence of ocular chlamydia (P = 0.32). This study found no evidence to support the theory that ompA diversity is associated with transmission of ocular chlamydia.