A high-carbohydrate diet prolongs dysbiosis and Clostridioides difficile carriage and increases late-onset CDI and mortality in a hamster model of infection

Studies using mouse models of Clostridioides difficile infection (CDI) have demonstrated a variety of relationships between dietary macronutrients on antibiotic-associated CDI; however, few of these effects have been examined in hamster models of CDI. In this study, we investigated the effect of a high-carbohydrate diet previously shown to protect mice from CDI on the progression and resolution of CDI in a hamster disease model. Hamsters fed the high-carbohydrate diet developed distinct diet-specific microbiomes during antibiotic treatment and CDI, with lower diversity, persistent C. difficile carriage, and delayed microbiome restoration. In contrast to 0% mortality in mice, 80% of hamsters fed the high-carbohydrate diet developed fulminant CDI and died, including several cases of late-onset CDI, whereas only 33% of hamsters fed a standard lab diet developed CDI only during the acute phase. We speculate that prolonged dysbiosis in these animals allowed C. difficile to proliferate following a three-day vancomycin course administered as part of this model system, leading to secondary CDI and eventual mortality. This study, along with similar studies in mouse models of CDI, suggests high-carbohydrate diets promote antibiotic-associated dysbiosis and long-term C. difficile carriage, which may convert to symptomatic CDI when conditions change. Importance The effects of diet on CDI are not completely known, although most studies in mouse CDI models show that dietary carbohydrates ameliorate CDI. Here, we used a high-carbohydrate diet previously shown to protect mice against CDI to assess its effect on a hamster model of CDI and paradoxically found that it promoted dysbiosis, C. difficile carriage, and higher mortality. A common thread in both mouse and hamster experimental models was that the high-carbohydrate diet promoted long-term carriage of C. difficile , which may have converted to fulminant CDI only in the highly susceptible hamster model system. If diets high in carbohydrates also promote dysbiosis and C. difficile carriage in humans, then these diets might paradoxically increase chances of CDI relapse despite their protective effects against primary CDI.