High-fat diet rewires gut host-microbiota relationship to derive worse outcomes following Clostridioides difficile infection

<i>Clostridioides difficile</i> is a leading cause of hospital-acquired enteric infections, with outcomes ranging from mild diarrhea to life-threatening pseudomembranous colitis and death. Dietary modulations can influence the course of antibiotic-induced <i>C. difficile</i> infection (CDI), and high-fat diets are associated with increased mortality. Here, we profiled host innate immune cells, cecal microbial composition, and the host transcriptome of normal diet (ND) and high-fat diet (HFD)-fed C57BL/6 male and female mice following experimental CDI during the acute and recovery phases. HFD-fed male mice exhibited delayed disease onset but increased mortality following CDI. During acute infection, HFD-fed males showed increased monocyte infiltration and expansion of CD103⁺CD11b^- and CD103^-CD11b⁺ dendritic cell subsets; transcriptomic modules were enriched for antigen presentation and signatures consistent with T cell activation, coincident with enrichment of <i>Escherichia</i> and <i>Lactococcus</i>. In contrast, during recovery, HFD-fed males and females displayed sustained neutrophil and monocyte infiltration, depletion of eosinophils (prominent in males), tissue-resident Tim4⁺/CD206⁺ macrophage subsets and ILC3s, increased expression of <i>Tlr4</i> and endothelial activation markers, downregulation of metabolic pathways, and failure to restore cecal microbial diversity. Collectively, these data indicate that high-fat feeding disrupts resolution programs after CDI and promotes progression to severe disease, with the most pronounced susceptibility in males.