The role of lactic acid production by probiotic Lactobacillus species in vaginal health.

Vaginal eubiosis is characterised by beneficial lactobacillus-dominated microbiota. In contrast, vaginal dysbiosis (e.g. bacterial vaginosis, BV), characterised by an overgrowth of multiple anaerobes, is associated with an increased risk of adverse urogenital and reproductive health outcomes. A major distinguishing feature between the vaginal environment in states of eubiosis and dysbiosis is a high concentration of lactic acid, produced by lactobacilli, that acidifies the vagina in eubiosis versus a sharp drop in lactic acid and an increase in pH in dysbiosis. Here we review the antimicrobial, antiviral and immunomodulatory properties of lactic acid and the use of lactic acid and lactobacilli probiotics in preventing or treating BV.