Effects of sexual dimorphism and estrous cycle on C. difficile infections in rodent models

Clostridioides difficile infection (CDI) is responsible for the majority of identifiable hospital-related antibiotic-associated diarrhea. Susceptibility to CDI and severity of disease varies depending on a variety of factors such as aggressive use of broad-spectrum antibiotics, age, and immune status. Epidemiological studies have consistently shown that female patients are more at risk for CDI than their male counterparts. In this study, we show that female mice developed more severe CDI than males when challenged with spores from three different C. difficile strains. CDI sexual dimorphism was still apparent when animals were placed under diet conditions that exacerbated CDI severity. Unlike male mice, females undergo the estrous cycle. Thus, female mice were challenged with C. difficile spores when they were at the estrus, metestrus, diestrus, late diestrus/early proestrus, proestrus, or late proestrus/early estrus stages. Animals were scored for CDI sign severity while continuously monitoring their estrous cycle stages. The resulting data showed a striking spike in CDI severity when animals were in proestrus the day before sign scoring. In contrast, animals who were in estrus the day before sign scoring were protected from CDI. Prophylactic treatment of CDI also showed sexual dimorphism with females responding better to treatment than males. Interestingly, infection sexual dimorphism was reversed in hamsters, with male hamsters developing more severe CDI signs than females. In conclusion, we have shown that mice recreate many of the conditions of sexual dimorphism of human CDI. ### Competing Interest Statement The authors have declared no competing interest.