Altenburg Our bowels contain billions of bacteria. Sometimes diarrhea occurs from an overgrowth of a particular bacteria called Clostridium difficile (C. diff), particularly after taking antibiotics that kill off regular gut bacteria. It appears that infants exposed to this bacteria develop protective antibodies that can protect against C. diff-associated diarrhea later in life. While researchers are still working to understand this better, we can all reduce our risks of coming down with C. diff-associated diarrhea by avoiding unnecessary antibiotics. Overuse of antibiotics is the most common and avoidable cause of C. diff overgrowth in the bowels and diarrhea from it.