Effect of metronidazole on concentrations of vaginal bacteria associated with risk of HIV acquisition

Abstract

Several bacterial vaginosis (BV)-associated bacteria have been associated with elevated risk of human immunodeficiency virus (HIV) acquisition; however, susceptibility of these bacteria to antibiotics is poorly understood. Vaginal samples were collected from 22 persons daily for 2 weeks following BV diagnosis. Metronidazole treatment was prescribed for 5–7 days. Changes in bacterial concentrations were measured with taxon-specific 16S rRNA gene quantitative PCR (qPCR) assays. A culture-based antimicrobial assay confirmed presence of antibiotics in vaginal swab samples. Bacterial DNA concentrations decreased during antibiotic administration for all 13 bacterial taxa tested. Comparison of bacterial DNA concentrations in samples before administration of antibiotics to samples taken on the last day of antimicrobial assay-confirmed antibiotic presence showed a 2.25–4.78 log10-fold decrease across all taxa. Concentrations were frequently reduced to the qPCR assay’s limit of detection, suggesting eradication of bacteria. Mean clearance time varied across taxa (1.2–7.9 days), with several bacteria (e.g., Sneathia spp., Vaginal TM7, and Eggerthella-like sp.) taking >7 days to suppress. Metronidazole reduces quantities of bacterial taxa associated with increased HIV acquisition risk.