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Clinical Significance

Clostridium difficile is the cause of antibiotic associated diarrhea (AAD) and pseudomembranous colitis (PMC). PMC is an inflammatory disease of the colon caused by toxins of C. difficile.

C. difficile produces two potent toxins:

  • Toxin A (TcdA), an enterotoxin
  • Toxin B (TcdB), a cytotoxin
It is the production of these toxins in the gastrointestinal tract that ultimately leads to disease. There is a relationship between toxin levels, the development of pseudomembranous colitis (PMC), and the duration of diarrhea.
For many years, toxin A was regarded as more important than toxin B in the disease process. Later on, disease producing strains producing only toxin B were identified. These strains produced serious disease, and toxin B was found to be responsible for more serious damage to intestinal cells.