Figure 1.

The vaginal environment during alternative states of eubiosis and BV. (A) During eubiosis, lactic acid-producing bacteria acidify the vaginal milieu pH <4.5 (average ~3.5) with lactic acid as the predominant metabolite. Lactic acid potently inactivates STIs while lactic acid-producers, such as Lactobacillus, generate a non-inflammatory environment. (B) During BV, the vaginal environment has a lower redox potential conducive to the growth of diverse anaerobic bacteria and higher bacterial load. The concentration of mixed SCFAs and amines also increase and is accompanied by loss of vaginal acidity pH >4.5. The diverse anaerobic bacteria generate virulence factors which compromise epithelial barrier integrity, degrade mucin and generate a pro-inflammatory environment.