Vaginal microbiota: Composition, protective role, associated pathologies, and therapeutic perspectives

Vaginal microbiota, mainly comprised of Lactobacillus crispatus, L. jensenii and L. gasseri, protect the mucosa against the establishment of pathogenic microorganisms through three complementary mechanisms: a) specific adherence to the epithelium, which blocks colonization of pathogens, b) production of antimicrobial compounds, and c) co-aggregation with pathogens, which enhances their microbiocidal effect. Despite these mechanisms, vaginal microbiota are sometimes displaced by undesirable microorganisms, which is associated with the development of bacterial vaginosis, vaginitis due to Candida spp., trichomoniasis, and lower urinary tract infections. On rare occasions, lactobacilli cause disease, but exclusively in immunocompromised patients. The main conditions are bacteremia (about 50% of the cases) and endocarditis (30%). However, no genital pathology caused by lactobacilli has been reported. The mutualistic effect of lactobacilli suggests that instillation of these microorganisms might regenerate the vaginal ecosystem, thus eliminating the relapses associated with treatment of the infection.