National Center for HIV/AIDS, Viral Hepatitis, STD and TB Prevention
Division of Sexually Transmitted Diseases
Program and Training Branch
Pathogenesis and Microbiology
Bacterial vaginosis is associated with the decrease or absence of protective lactobacilli, which are normally present in the vagina. Lactobacilli produce lactic acid from glycogen, maintaining the vagina's acidic pH. This acid environment inhibits the growth of other bacterial species found in the vagina in low levels. When lactobacilli are lacking, overgrowth of bacteria, such as Haemophilus spp., Gardnerella vaginalis, Bacteroides spp., Mycoplasma hominis, Mobiluncus spp., peptostreptococci, ureaplasma, and other anaerobes can occur.
One species of lactobacillus also produces hydrogen peroxide (H2O2), which is in vitro, toxic to viruses such as HIV as well as to bacteria. This species is present in approximately 42%-74% of females, and is under investigation as a
probiotic. The prevalence of BV in these women is low (4%).