Clostridium difficile is a major cause of diarrhea, responsiible for almost all cases of the life-threatening pseudomembranous colitis (PMC) and about a quarter of antibiotic-associated diarrheas (AAD). C.difficile is a normal component of the fecal flora in 2-3% of healthy adults, however is much more common in hospitalised patients.

Antibiotic treatment can cause suppression of the more predominent organisms making up the fecal flora and so can lead to proliferation of C.difficile, normally only a minor component. Many antibiotic drugs are thought to be predisposed to AAD and PMC, however clindamycin, ampicillin and the cephalosporins are the more commonly asscoiated. Pathogenic strains produce two polypeptide toxins (A and B). Toxin A is an enterotoxin causing excessive fluid secretion and inflammation, whereas toxin B is a cytotoxin.

Treatment. Fluid replacement and cessation of the predisposing antibiotic are the usual approaches to treatment, however in the more severe cases metronidazole or vancomycin may also be used.