The toxin producer Clostridium difficile is one of the most important pathogens of antibiotic-associated diarrhea and colitis and the cause of practically all cases of pseudomembranous colitis. Although around 2% of all healthy adults are colonized with C. difficile, many patients acquire this organism through nosocomial infections. Most antibiotics are said to promote the proliferation of the toxin producer C. difficile by destroying the natural intestinal flora. Two toxins, toxin A and toxin B, have been implicated in the disease caused by C. difficile. Toxin A is described as an enterotoxin, which causes an increase in intestinal permeability with subsequent accumulation of intestinal fluid and diarrhea. Toxin B is a powerful cytotoxin that causes cells to round off in cell cultures. The role of toxin B in the development of bowel disease is unclear. However, it has been hypothesized that the two proteins act synergistically in vivo. Some strains also express the binary toxin (encoded by the cdtA / B genes), which damages human cells by inhibiting actin polymerization.