Morbidity and mortality associated with GBS begin with colonization of the female reproductive tract (FRT). To date, our understanding of the factors required for GBS persistence in this environment remain limited.
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 modified an established mouse vaginal colonization model to explore 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, but did not contribute to colonization in vivo. Thus, we screened a low-complexity transposon (Tn) mutant library to identify novel genes important for E. faecalis colonization and persistence in the vaginal tract. This screen revealed 383 mutants that were underrepresented during vaginal colonization at 1, 5 and 8 days post-inoculation compared to growth in culture medium. We confirmed that mutants deficient in ethanolamine catabolism or in 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. IMPORTANCE Despite increasing prevalence and association of E. faecalis with aerobic vaginitis, essentially nothing is known about the bacterial factors that influence E. faecalis vaginal colonization. We have adapted an animal model of vaginal colonization that supports colonization of multiple E. faecalis strains. Additionally, we determined that ethanolamine utilization and type VII secretion system genes contribute to vaginal colonization and persistence. Identification of factors important for vaginal colonization and persistence provides potential targets for the development of therapeutics. This study is the first to identify key determinants that promote vaginal colonization by E. faecalis, which may represent an important reservoir for antibiotic resistant enterococci.
21Enterococcus faecalis is a Gram-positive commensal bacterium native to the gastrointestinal tract and an 22 opportunistic pathogen of increasing clinical concern. E. faecalis also colonizes the female reproductive 23 tract and reports suggest vaginal colonization increases following antibiotic treatment or in patients with 24 aerobic vaginitis. Currently, little is known about specific factors that promote E. faecalis vaginal 25 colonization and subsequent infection. We developed a mouse model of E. faecalis vaginal carriage and 26 demonstrate that both vancomycin resistant and sensitive strains colonize the murine vaginal tract. 27Following vaginal colonization, we observed E. faecalis in vaginal, cervical and uterine tissue. A mutant 28 lacking endocarditis-and biofilm-associated pili (Ebp) exhibited a decreased ability to associate with 29 human vaginal and cervical cells in vitro as well as ascend to the cervix and uterus in vivo. To further 30 identify novel factors that promote vaginal colonization, we screened a low-complexity transposon (Tn) 31 mutant library to identify genes important for E. faecalis persistence in the vaginal tract. This screen 32 revealed 383 mutants that were underrepresented during vaginal colonization at all time points compared 33 to growth in culture medium. We confirmed that mutants deficient in ethanolamine catabolism and the 34 type VII secretion system were attenuated in persisting during vaginal colonization. These results reveal 35 the complex nature of vaginal colonization and suggest that multiple factors contribute to E. 36 faecalis persistence in the reproductive tract. 37 38 IMPORTANCE 39Despite increasing prevalence and association of E. faecalis with aerobic vaginitis, essentially nothing is 40 known about the bacterial factors that influence E. faecalis vaginal colonization. We have established an 41 animal model of vaginal colonization that supports colonization of multiple E. faecalis strains. 42Additionally, we determined that pili, ethanolamine utilization, and type VII secretion system genes 43 3 contribute to vaginal persistence and ascension to reproductive tract tissues. Identification of factors 44 important for vaginal colonization and persistence provides potential targets for the development of 45 therapeutics. This study is the first to identify key determinants that promote vaginal colonization by E. 46 faecalis, which may represent an important reservoir for antibiotic resistant enterococci. 47 48 INTRODUCTION 49Enterococcus faecalis is an opportunistic pathogen that resides in the human gastrointestinal and 50 urogenital tracts [1, 2]. While E. faecalis colonization is normally asymptomatic, certain populations are 51 at risk for severe disease including urinary tract infections (UTIs), wound infections, pelvic inflammatory 52 disease (PID), infective endocarditis, and adverse birth effects during pregnancy [3, 4]. Enterococcal 53 infections are often associated with the production of biofilms, assemblages of microbes enclosed in an 54 extracellula...
Pre-term birth, miscarriage, and other adverse pregnancy outcomes remain the primary cause of neonatal death and are associated with bacterial ascending infections within the female reproductive tract. Group B Streptococcus (GBS), a vaginal tract colonizer, is a leading contributor to adverse pregnancy outcomes and neonatal invasive disease. We have developed a mouse model of GBS vaginal colonization and ascending infection and have observed increased IL-17 production in mice that cleared GBS colonization compared to those still colonized. Thus, we hypothesize that IL-17 and IL-17-producing cells may be important for host defense; yet, the immune dynamics during GBS vaginal persistence and ascending infection/adverse pregnancy outcomes remain unknown. T cells are a major source of IL-17 in the mucosa. To assess the role of adaptive immunity during GBS colonization, we colonized RAG1+/+ and RAG1−/− mice with GBS and observed increased persistence of GBS in the vaginal tract of the RAG1−/− mice. To determine the cellular source of IL-17 within the reproductive tract of GBS-colonized mice, we isolated immune cells from vaginal, cervical, and uterine tissues at the time of GBS clearance and performed flow cytometry. TCRɣδ+ cells comprised the highest percentage of RORɣT+ immune cells in the vagina, cervix, and uterus. We further observed an increased percentage of TCRɣδ+ cells in the uterus of GBS-colonized mice compared to naïve mice at day 9 post-inoculation, at which point half the mice had cleared. We hypothesize that IL-17-producing TCRɣδ+ cells contribute to GBS clearance in the murine reproductive tract. Future studies will assess GBS vaginal persistence and ascending infection in IL-17- and TCRɣδ-deficient mouse lines.
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