Social, microbial, and immune factors linking bacterial vaginosis and infectious diseases

Bacterial vaginosis (BV) is a polymicrobial condition of the vaginal microbiota associated with a variety of sexually transmitted infections, infections of maternal and fetal tissues during pregnancy, and even some infections outside of the reproductive tract, including the urinary tract and mouth. BV has also been associated with conditions in which the body generates prominent inflammatory reactions to microbes, including infections of the cervix and other upper genital tract tissues. For reasons still not understood, BV is a highly recurrent and often difficult-to-treat condition, complicating attempts to prevent these associated infections. An additional layer of complexity arises from the increasing awareness that the presence of BV-associated bacteria in the vagina is not always symptomatic or associated with adverse outcomes. In this concise Review, we summarize and synthesize three groups of factors grounded in the literature that may be fueling the associations between BV and infection: (a) aspects of society and culture; (b) pathogens, virulence factors, and processes of microbial antagonism and synergy; and (c) host factors, such as genetics and immunity. Our goal is to understand what contexts and combinations of microbial, host, and social factors conspire to make BV virulent in some individuals but not others. Disrupting these patterns more systematically may achieve healthier outcomes.