Clostridium difficile infection (CDI) is a leading cause of nosocomial-associated gastrointestinal illness including self-limited diarrhoeal disease, pseudomembranous colitis and fatal toxic megacolon. C. difficile is a Gram-positive, spore-forming anaerobic bacillus. It produces A (enterotoxin) and B (cytoxoin) toxins that cause disease. The organism is part of the normal flora of the human gut. Antibiotic treatment eliminates normal flora but not spores of C. difficile, which then grow in the gastro-intestinal tract and cause disease. C. difficile is often nosocomially transmitted because spores are highly resistant to decontamination.