The vaginal microbiome (VMB) is a dynamic microecosystem consisting of bacteria, yeast and fungi. These microbes protect the vagina against infection, support vaginal mucosal health and may also support healthy pregnancy outcomes. Unlike the gut microbiome, a healthy VMB thrives on low microbial diversity and is typically dominated by one of the following Lactobacillus species: L. crispatus, L. gasseri, L. iners and L. jensenii. As the name implies, the primary function of Lactobacillus species is to produce lactic acid to support vaginal acidity. L. crispatus, L. gasseri, and L. jensenii do a great job at this.
L. iners, on the other hand, is more unpredictable. This is because L. iners produces L-actic acid, rather than D-lactic acid, which is less successful at promoting vaginal acidity. VMBs dominated by L. iners have more fluctuations in community composition and are more susceptible to infection. Lactobacillus species also produce bacteroicins (antimicrobial compounds) and take up real estate along the vaginal walls so that unwanted microbes cannot thrive. These mechanisms support thriving mucosal health to stave off vaginal dryness and discomfort. If Lactobacillus abundance drops, unwanted microbes have an opportunity to take over. This can lead to a thinning of the vaginal mucosa, vaginal dryness, abnormal discharge, itching, pain, increased risk of infection and other adverse symptoms.