A clinical and epidemiological review of non-toxigenic Clostridium difficile.

Clostridium difficile is a significant nosocomial threat to human health and is the most commonly identified cause of antibiotic-associated diarrhea. The development of C. difficile colitis requires production of toxins A and/or B, but some strains do not express these proteins. These non-toxigenic C. difficile (NTCD) have garnered attention for their capacity to colonize humans and potentially reduce the risk for symptomatic colitis caused by toxigenic strains. Isolates of NTCD have been obtained from the environment as well as from animal and human sources. Studies in a hamster CDI model have demonstrated a protective effect of NTCD against toxigenic infection. The extent to which this protective effect of NTCD occurs in humans remains to be defined. Evidence for a therapeutic or preventive role for NTCD is limited but clinical prophylaxis studies are ongoing. NTCD potentially represents an exciting new tool in preventing CDI and its recurrences.