Effects of Nonoxynol-9 on Vaginal Microflora and Chlamydial Infection in a Monkey Model

BACKGROUND AND OBJECTIVES: Nonoxynol-9, an intravaginal microbicide, is chlamydiacidal in vitro but also cytotoxic. This study examines the effects of nonoxynol-9 in vivo, using a pigtail macaque model of chlamydial cervicitis. GOALS: To establish a minimum infectious dose of Chlamydia trachomatis in the macaque, and to observe the effects of a single dose of nonoxynol-9 on efficiency of chlamydial infection, vaginal microflora, and cervicovaginal irritation. STUDY DESIGN: The effects of 4% nonoxynol-9, C. trachomatis (5,000 or 10,000 IFU) or both nonoxynol-9 application and chlamydial infection were studied in 17 macaques. RESULTS: Following a single application of nonoxynol-9, chlamydial infection was prevented in 4 of 6 monkeys infected with 10,000 IFU; there was a transient decrease in anaerobic gram-negative rods (P < 0.05) and Peptostreptococci (P > 0.05), but no change in Lactobacillus. Mild cervicovaginal irritation was observed in the monkeys. CONCLUSIONS: A single dose of nonoxynol-9 causes minimal vaginal flora and epithelial irritation, and may be useful for prevention of chlamydial infection.