Indole intercepts the communication between enteropathogenic E. coli and Vibrio cholerae

Reported numbers of diarrheal samples exhibiting co-infections or multiple infections, with two or more infectious agents, are rising, likely due to advances in bacterial diagnostic techniques. Bacterial species detected in these samples include Vibrio cholerae (V. cholerae) and enteropathogenic Escherichia coli (EPEC), which infect the small intestine and are associated with high mortality rates. It has previously been reported that EPEC exhibit enhanced virulence in the presence of V. cholerae owing to their ability to sense and respond to elevated concentrations of cholera autoinducer 1 (CAI-1), which is the primary quorum-sensing (QS) molecule produced by V. cholerae. In this study, we examined this interspecies bacterial communication in the presence of indole, a major microbiome-derived metabolite found at high concentrations in the human gut. Interestingly, we discovered that although indole did not affect bacterial growth or CAI-1 production, it impaired the ability of EPEC to enhance its virulence activity in response to the presence of V. cholerae. Furthermore, the co-culture of EPEC and V. cholerae in the presence of B. thetaiotaomicron, an indole-producing commensal bacteria, ablated the enhancement of EPEC virulence. Together, these results suggest that microbiome compositions or diets that influence indole gut concentrations may differentially impact the virulence of pathogens and their ability to sense and respond to competing bacteria.

Automated summary

The number of co-infections or multiple infections in reported diarrheal samples is increasing, possibly due to advances in bacterial diagnostic techniques. Vibrio cholerae and enteropathogenic Escherichia coli (EPEC) are commonly detected bacterial species in these samples, associated with high mortality rates. This study investigated the interspecies bacterial communication between EPEC and V. cholerae in the presence of indole, a major microbiome-derived metabolite found in the human gut. The results suggest that indole impairs the ability of EPEC to enhance its virulence activity in response to V. cholerae, and the composition of the microbiome or diets that influence indole gut concentrations may differentially impact pathogen virulence and their ability to sense and respond to competing bacteria.