Pathogenic C diff strains can produce multiple toxins. The two most commonly studied and characterized toxins are toxin A (C diff enterotoxin A) and toxin B (C diff cytotoxin B). Both toxins can produce diarrhea and inflammation. The toxins function by damaging the intestinal mucosa causing the various symptoms of CDI including colitis. Toxin A is an enterotoxin that disrupts the intestinal cell wall leading to diarrhea while toxin B is a cytotoxin that is toxic to the cells of the colon thereby causing inflammation.
Although the precise mode of action of these two toxins is currently not completely understood, studies suggest that toxin A and B are glucosyltransferases that target and inactivate the Rho family of GTPases. (The Rho GTPases are key proteins involved in many biological processes and signaling pathways. Inactivation of these proteins leads to cytopathic and cytotoxic effects and immune responses in the host cells).