What is causing active trachoma? The role of nonchlamydial bacterial pathogens in a low prevalence setting.

PURPOSE In low prevalence settings, clinically active follicular trachoma (TF) is often found in the absence of detectable Chlamydia trachomatis. The reasons for this persistent follicular phenotype are not well understood; one possible explanation is that other bacterial species are provoking the inflammatory response. This study investigated the relationship between TF, C. trachomatis, and nonchlamydial bacterial infection. METHODS A cross-sectional survey was conducted in a trachoma endemic village in Tanzania. All available children were examined for trachoma and swabs were collected for microbiologic culture (blood and chocolate agar) and C. trachomatis PCR (Amplicor). RESULTS Four hundred seventy-three children under 10 years of age were recruited for this study. The prevalences of TF and C. trachomatis were 13.7% and 5.3%, respectively, and were not associated. Bacteria were cultured from 305 (64.5%) swab samples; 162 (34.3%) grew a pathogen (with or without a commensal organism) and 143 (30.2%) grew commensal bacteria only. The most common pathogens were Streptococcus pneumoniae and Haemophilus influenzae (type B and non-type B). The presence of bacterial pathogens was associated with TF (odds ratio, 4.68; 95% confidence interval, 2.31-9.50; P < 0.001). CONCLUSIONS In regions with low levels of endemic trachoma, it is possible that much of the TF that is observed is attributable to nonchlamydial bacterial pathogens. It is plausible that individuals who have previously developed a follicular conjunctivitis in response to C. trachomatis may more readily reform conjunctival follicles when challenged with certain other bacterial species.