A two-hour anaerobic exposure to 100 mM H2O2 with 50 mU/mL MPO at pH 7 reduced the viability of all four vaginal lactobacilli species and all seventeen BV-associated bacterial species to undetectable levels (a measured reduction of between 106 and 109 organisms per mL, depending on the initial bacterial concentration). The gene discussed is MPO; the disease is bacterial vaginosis.