Differential effects of Clostridium difficile toxins A and B on rabbit ileum

Gastroenterology. 1987 Aug;93(2):273-9. doi: 10.1016/0016-5085(87)91014-6.


The pathogenesis of Clostridium difficile enterocolitis appears to involve colonization of the bowel followed by release of toxin A, an enterotoxin, and toxin B, a cytotoxin. The purpose of this study was to determine the effect of purified toxins A and B on intestinal secretion, epithelial permeability, and morphology in perfused rabbit ileal loops. Intestinal permeability after toxin exposure was assessed by blood-to-lumen clearance of [3H]mannitol. Toxin A at doses of 5-100 micrograms/10 cm ileal loop caused a threefold to fivefold increase in [3H]mannitol permeability (p less than 0.001) vs. equal concentrations of toxin B or buffer control. In addition, perfusate from toxin A-exposed loops contained significantly more neutrophils (p less than 0.001) than toxin B or control loops. Toxin A caused severe epithelial cell necrosis with destruction of villi and polymorphonuclear infiltration. Electron microscopy of mucosa subjected to a low dose of toxin revealed widespread nonspecific dilatation of endoplasmic reticulum and mitochondrial swelling. In contrast to these effects of toxin A in ileal loops, in vitro experiments with ileal explants in short-term organ culture revealed that toxin A had no effect on epithelial cell permeability, protein synthesis, release of alkaline phosphatase, or morphology. Our results show that purified toxin A but not toxin B causes severe inflammatory enteritis in rabbit ileal loops, but has no discernable effect on rabbit ileum in vitro. We speculate that toxin A may contribute significantly to intestinal damage in C. difficile-associated colitis and diarrhea.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Bacterial Toxins / pharmacology*
  • Clostridium Infections / etiology
  • Clostridium*
  • Ileitis / etiology
  • Ileum / drug effects*
  • Ileum / pathology
  • Ileum / ultrastructure
  • Male
  • Organ Culture Techniques
  • Rabbits


  • Bacterial Toxins