Toxin A of Clostridium difficile is a potent cytotoxin.

Clostridium difficile is the cause of antibiotic-associated colitis in humans. The organism produces toxin A, which is generally known as the enterotoxin, and toxin B, which is known as the cytotoxin. Toxin A has been reported to have slight cytotoxic activity; in this study we show that cell lines (F9, OTF9-63, and P19) which express a carbohydrate to which toxin A binds are more sensitive to the toxin. These cell lines can be used as research tools for determining concentrations of biologically active toxin A and should also prove useful for studies of the mechanism of action of the toxin.