CT-induced disease generates epithelial cell-derived L-lactate that promotes Vibrio cholerae growth in the small intestine

Cholera toxin (CT) promotes Vibrio cholerae colonization by altering gut metabolism to favor pathogen growth. We have previously found that CT-induced disease leads to increased concentrations of L-lactate in the lumen of the small intestine during experimental cholera. Here, we show that CT-induced disease leads to the upregulation of mammalian lactate dehydrogenase A (LDHA), an enzyme that catalyzes the conversion of pyruvate to L-lactate, in small intestinal epithelial cells. In a suckling mouse model, the bacterial L-lactate dehydrogenase (LldD) conferred a fitness advantage to V. cholerae but not to the {Delta}ctxAB mutant incapable of producing CT. Finally, the fitness advantage conferred by LldD was significantly reduced in mice lacking epithelial-cell specific LDHA, demonstrating that epithelial-derived L-lactate is a major contributor to CT-dependent pathogen expansion. These findings identify L-lactate as a host-derived metabolite generated by intestinal epithelial cells produced during cholera disease that directly fuels V. cholerae growth during infection, uncovering a mechanism by which CT confers a fitness advantage to the pathogen during disease.