The condition is very frequently seen after the use of clindamycin, cephalosporins and (less often) penicillin, because these antibiotics kill the normal bowel flora that generally keeps the bacteria Clostridium difficile under control. This bacterium produces toxin that cause the symptoms.
The disease can be treated with oral doses of vancomycin. Vancomycin cannot be absorbed from the bowels, so its concentration there will be high, and it kills the C. difficile.