Murine Model of Candida albicans and Streptococcus agalactiae Vaginal Co-Colonization

Diverse microbes are isolated from the human vaginal tract, and many of the organisms that inhabit this niche can switch between commensal and pathogenic lifestyles. Factors, including community composition and the host environment, influence disease outcomes; however, the mechanisms determining these outcomes are not well understood. In this manuscript, we describe a murine model to investigate interkingdom interactions and the host response to Candida albicans and Streptococcus agalactiae (Group B Streptococcus, GBS), pathobionts that colonize the female genital tract (FGT). Emerging evidence suggests that C. albicans colonization is a risk factor for GBS carriage due to their frequent co-isolation. During pregnancy, GBS colonization can lead to adverse outcomes including chorioamnionitis and stillbirth. GBS can also be transmitted to a fetus in utero or a neonate during birth and is a leading cause of neonatal meningitis. Colonization of the vaginal tract is a critical precursor to GBS disease, and this niche exerts numerous selective pressures, some of which may be influenced by C. albicans colonization. This protocol describes a model of concurrent C. albicans-GBS vaginal co-colonization using antibiotic treatment and a single dose of 17β-estradiol to establish C. albicans colonization, followed by the removal of antibiotics and inoculation with GBS. Microbial burdens in the vaginal lumen are quantified over the course of the experiment by lavage, and burdens throughout the FGT are quantified by dissection, homogenization, and plating of the vagina, cervix, and uterus. This method will enable investigation of the mechanisms by which direct and indirect polymicrobial interactions influence the lifestyles and pathogenesis of these two organisms, as well as the host immune landscape in the FGT.