Background: It has long been assumed that a healthy acidic vaginal environment inhibits infection by Chlamydia trachomatis. The research objectives were to evaluate the effect of pH on C trachomatis infection by two in vitro methods, to assess pH effect at different serial dilutions of C trachomatis elementary bodies (EBs), and to examine protection by an antibiotic peptide, protegrin (PG-1), over a pH range.
Goals: The goals of this study were to test the hypothesis that acidic pH inhibits C trachomatis infection and to determine the ability of PG-1 to provide protection at acidic and neutral pH.
Study Design: The effect of pH on C trachomatis was examined using two pH-adjusted preincubation shell vial assays. C trachomatis EBs (serovars L2, D, and E) were exposed to pH-adjusted media, with and without PG-1, and infection was assessed by inclusion forming unit (IFU) formation in McCoy cell monolayers.
Results: Acidic pH in preincubation media markedly decreased IFUs by both in vitro methods. Serial dilution experiments showed a 3- to 10-fold reduction in IFUs for C trachomatis (L2 and E) at pH 5.0, compared with those at pH 7.5. C trachomatis (D) showed a 17- to 23-fold reduction in IFUs (serial dilutions 1:1–1:4). PG-1 protected McCoy cell monolayers from infection by C trachomatis after exposure to varied pH environments.
Conclusion: Acidic pH exposure significantly reduced C trachomatis infection in vitro. Our results support the hypothesis that a healthy acidic vaginal environment protects women from C trachomatis infection. In addition, antibiotic peptides may provide protection as topical microbicides, regardless of vaginal pH.