Diet composition drives tissue-specific intensity of murine enteric infections
Diet composition plays a large role in regulating of gut health and enteric infection. In particular, synthetic Western-style diets may predispose to disease, whilst whole-grain diets containing high levels of crude fiber are thought to promote gut health. Here we show that, in contrast to this paradigm, mice fed unrefined chow are significantly more susceptible to infection with Trichuris muris, a caecum-dwelling nematode, than mice given refined, semi-synthetic diets (SSD). Moreover, mice fed SSD supplemented with inulin, a fermentable fiber, developed chronic T. muris burdens whereas mice given SSD efficiently cleared the infection. Diet composition significantly impacted infection-induced changes in the host gut microbiome. Mice infected with the bacterium Citrobacter rodentium were also more susceptible to pathogen colonization when fed either chow or inulin-enriched SSD. However, transcriptomic analysis of tissues from mice fed either SSD or inulin-enriched SSD revealed that, in contrast to T. muris, increased C. rodentium infection appeared to be independent of the host immune response. Accordingly, exogenous treatment with IL-25 partially reduced T. muris burdens in inulin-fed mice, whereas IL-22 treatment was unable to restore resistance to C. rodentium colonization. Diet-mediated effects on pathogen burden were more pronounced for large intestine-dwelling pathogens, as effects on small intestinal helminth (Heligmosomoides polygyrus) were less evident, and protozoan (Giardia muris) infection burdens were equivalent in mice fed chow, inulin-enriched SSD, or SSD, despite higher cyst excretion in chow-fed mice. Collectively, our results point to a tissue- and pathogen-restricted effect of dietary fiber levels on enteric infection intensity. ImportanceEnteric infections induce dysbiosis and inflammation and are a major public health burden. As the gut environment is strongly shaped by diet, the role of different dietary components in promoting resistance to infection is of interest. Whilst diets rich in fiber or whole grain are normally associated with improved gut health, we show here that these components predispose the host to higher levels of pathogen infection. Thus, our results have significance for interpreting how different dietary interventions may impact on gastrointestinal infections. Moreover, our results may shed light on our understanding of how gut flora and musical immune function is influenced by the food that we eat.