Vaginal Lactobacillus strains interfere with Chlamydia trachomatis infection

Lactobacilli play a pivotal role in the maintenance of the homeostasis of the vaginal ecosystem, establishing mutualistic synergies with the female host and preventing the overgrowth of exogenous pathogens, including sexually transmitted microorganisms. Chlamydia trachomatis is an obligate intracellular bacterium and represents a leading cause of sexually transmitted disease worldwide; if left untreated, can induce severe sequelae in women, as pelvic inflammatory disease and infertility. We investigated the in vitro activity of a panel of vaginal Lactobacillus strains (belonging to L. crispatus, L. gasseri, and L. vaginalis species) against C. trachomatis infectivity in human cervical cells (HeLa cells). We demonstrated that vaginal lactobacilli are effective in inhibiting C. trachomatis infectious process, the antagonistic activity is specific for Lactobacillus and L. crispatus is the most active species. We then focused on the molecular basis of the anti-Chlamydia activity exerted by L. crispatus, and we showed that Lactobacillus induces modifications in the lipid organization of HeLa plasma membrane and reduces 51 integrin exposure. We thus identified a molecular mechanism underlying the protective effect of vaginal Lactobacillus towards C. trachomatis infection, getting insights into the role of cervico-vaginal microbiota in woman’s health.