Clostridium difficile Modulates the Gut Microbiota by Inducing the Production of Indole, an Interkingdom Signaling and Antimicrobial Molecule

Clostridium difficile infection is the leading cause of hospital-acquired and antibiotic-associated diarrhea worldwide. C. difficile flourishes in the colon after the diversity of the beneficial and protective gut microbiota have been altered by antibiotic therapy. C. difficile tends to persist, as does dysbiosis, encouraging recurrence a few days to weeks after treatment, and this further complicates treatment options. Here, we show that C. difficile might persist by manipulating the indigenous microbiota to produce indole, a bioactive molecule that inhibits the growth and reconstitution of the protective gut microbiota during infection. This discovery may explain a unique strategy C. difficile uses to control other bacteria in the colon and provide insight into the complex interactions and chemical warfare among the gut microbiota.