Mouse microbiota upon Salmonella infection

Mice were fed a fibre-rich, plant-based diet (PD), or a Westernized diet rich in animal fat and proteins and in simple sugars for two weeks, and then infected with S. Typhimurium strain ST4/74 invA. Twenty-four hours post infection, fecal pathogen loads were equal in both diet groups, suggesting that neither of the diets had negatively influenced the ability of ST4/74 invA to colonize and proliferate in the gut at this time point. To define its diet-dependent gene expression pattern, S. Typhimurium was immunomagnetically isolated from the gut content, and its transcriptome was analyzed. A total of 66 genes were more strongly expressed in mice fed the plant-based diet. The majority of these genes was involved in metabolic functions degrading substrates of fruits and plants. Four of them are part of the gat gene cluster responsible for the uptake and metabolism of galactitol and D-tagatose. Competitive mice infection experiments performed with strain ST4/74 and ST4/74 STM3254 lacking tagatose-1,6-biphosphate aldolase, which is essential for galactitol and tagatose utilization, revealed a prolonged survival of strain ST4/74 in the gastrointestinal tract of mice fed plant-based diet in comparison with the deletion mutant. In line with this finding, 16S rRNA amplicon analysis revealed higher abundance of bacterial families able to degrade fiber and nutritive carbohydrates in PD-fed mice in comparison with those fed a WD diet.