Colonic phosphocholine is correlated with Candida tropicalis and promotes diarrhea and pathogen clearance.

Diarrhea is characterized by alterations in the gut microbiota, metabolites, and host response to these changes. Studies have focused on the role of commensal bacteria in diarrhea; however, the effect of fungi on its pathogenesis remains unexplored. Here, using post-weaned piglets with or without diarrhea, we found an unexpected decrease in the abundance of Candida tropicalis in diarrheal piglets. We also observed increased accumulation of reactive oxygen species (ROS) and the formation of neutrophil extracellular traps (NETs) in the colonic tissues of diarrheal piglets. Using dectin-1-knockout mice, we found that the over-accumulation of ROS killed C. tropicalis by promoting NET formation, which was dependent on dectin-1. The decreased abundance of C. tropicalis resulted in reduced phosphocholine consumption. Then, colonic phosphocholine accumulation drives water efflux by increasing cAMP levels by activating adenylyl cyclase, which promotes the clearance of pathogenic bacteria. Collectively, we demonstrated that phosphocholine is correlated with colonic C. tropicalis and promotes diarrhea and pathogen clearance. Our results suggest that mycobiota colonizing the colon might be involved in maintaining intestinal metabolic homeostasis through the consumption of certain metabolites.