Intestinal beta-lactamase activity in ampicillin-induced, Clostridium difficile-associated ileocecitis.

Daily oral administration of ampicillin to hamsters consistently resulted in fatal ileocecitis due to ampicillin-susceptible strains of Clostridium difficile. Ampicillin was not detected in the cecal contents of these hamsters once C. difficile appeared. Cecal contents obtained from hamsters with ampicillin-induced ileocecitis displayed beta-lactamase activity, whereas cecal contents obtained from untreated control hamsters did not. Colonization of the ceca with C. difficile corresponded to a decrease in the concentration of cecal ampicillin below the minimum inhibitory concentration effective against C. difficile in vitro. The concomitant administration of ampicillin and sulbactam, a nonabsorbable beta-lactamase inhibitor, protected hamsters from developing fatal ileocecitis. However, ileocecitis developed upon the discontinuation of treatment. beta-Lactamase produced by the cecal flora inactivates ampicillin present in the intestinal tract, thereby permitting ampicillin-sensitive C. difficile to multiply and cause disease.