Clostridium difficile causes antibiotic-associated diarrhea (AAD) and more serious intestinal conditions such as colitis and pseudomembranous colitis in humans. These conditions generally result from overgrowth of Clostridium difficile in the colon, usually after the normal intestinal microbiota flora has been disturbed by antimicrobial chemotherapy.

People in good health usually do not get C. difficile disease. Individuals who have other conditions that require prolonged use of antibiotics and the elderly are at greatest risk. Also, individuals who have recently undergone gastrointestinal surgery, or have a serious underlying illness, or who are immunocompromised, are at risk.

C. difficile produces two toxins: Toxin A is referred to as an enterotoxin because it causes fluid accumulation in the bowel. Toxin B is an extremely lethal (cytopathic) toxin.

Stool cultures for diagnosis of the bacterium may be complicated by the occurrence and finding of non toxigenic strains of the bacterium, so the most reliable tests involve testing for the presence of the Toxin A and/or Toxin B in the stool. The toxins are very unstable. They degrade at room temperature and may be undetectable within two hours after collection of a stool specimen leading to false negative results of the diagnosis.

In the hospital and nursing home setting, C. difficile infections can be minimized by judicious use of antibiotics, use of contact precautions with patients with known or suspected cases of disease, and by implementation of an effective environmental and disinfection strategy.

Clostridium difficile infections can usually be treated successfully with a 10-day course of antibiotics including metronidiazole or vancomycin (administered orally).

C. difficile colonies on blood agar

C. difficile endospores.