Objective Trichomonas vaginalis (TV) is common in HIV+ women, and host factors may play a role in TV treatment outcomes. The purpose of this study was to examine the influence of bacterial vaginosis (BV) on the response to TV treatment among HIV+ women.

Methods A secondary analysis was conducted of a clinical trial which randomised HIV+/TV+ women to metronidazole (MTZ) treatment: 2 g (single-dose) versus 7 day 500 mg twice daily (multidose). BV was classified using Nugent scores from baseline Gram stains. Women were recultured for TV at test-of-cure (TOC) and again at 3 months if TV-negative at TOC. Repeat TV infection rates were compared for women with a baseline TV/BV coinfection versus baseline TV infection only, and stratified by treatment arm.

Results Among 244 HIV+/TV+ women (mean age=40.3, ±9.5; 92.2% African–American), the rate of BV was 66.8%. Women with BV were more likely to report douching and ≥1 recent sex partners. HIV+ women with baseline TV/BV coinfection were more likely to be TV-positive at TOC than women with baseline TV infection only (RR 2.42 (95% CI 0.96 to 6.07; p=0.05)). When stratified by treatment arm, the association was only found in the single-dose arm (p=0.02) and not in the multidose arm (p=0.92). This interaction did not persist at 3 months.

Conclusions For HIV+/TV+ women, the rate of BV was high, and BV was associated with early failure of the MTZ single-dose treatment for TV. Biological explanations require further investigation.