Genome-wide mutagenesis identifies factors involved in Enterococcus faecalis vaginal adherence and persistence

Enterococcus faecalis is a Gram-positive commensal bacterium native to the gastrointestinal tract and an opportunistic pathogen of increasing clinical concern. E. faecalis also colonizes the female reproductive tract and reports suggest vaginal colonization increases following antibiotic treatment or in patients with aerobic vaginitis. Currently, little is known about specific factors that promote E. faecalis vaginal colonization and subsequent infection. We developed a mouse model of E. faecalis vaginal carriage and demonstrate that both vancomycin resistant and sensitive strains colonize the murine vaginal tract. Following vaginal colonization, we observed E. faecalis in vaginal, cervical and uterine tissue. A mutant lacking endocarditis- and biofilm-associated pili (Ebp) exhibited a decreased ability to associate with human vaginal and cervical cells in vitro as well as ascend to the cervix and uterus in vivo. To further identify novel factors that promote vaginal colonization, we screened a low-complexity transposon (Tn) mutant library to identify genes important for E. faecalis persistence in the vaginal tract. This screen revealed 383 mutants that were underrepresented during vaginal colonization at all time points compared to growth in culture medium. We confirmed that mutants deficient in ethanolamine catabolism and the type VII secretion system were attenuated in persisting during vaginal colonization. These results reveal the complex nature of vaginal colonization and suggest that multiple factors contribute to E. faecalis persistence in the reproductive tract.