The gram-positive anaerobic bacillus Clostridium difficile is the leading causative agent of antibiotic-associated diarrhea and pseudomembranous colitis.This pathogen is capable of causing disease that could be severe or fatal if not diagnosed on time and treated. Exposure to antibiotics is the major risk factor for C. difficile infection. Infection can develop if the normal gastrointestinal flora is disrupted by antibiotic therapy and a person acquires toxin-producing C. difficile, typically via the fecal-oral route. C. difficile’s key virulence factors are toxin A and toxin B. These toxins show high sequence and functional homology. Toxin A has been described as a tissue damaging enterotoxin which attracts neutrophils and monocytes and toxin B as a potent cytotoxin that degrades the colonic epithelial cells. Most virulent strains produce both toxins, however, strains that are toxin A negative and toxin B positive are also capable of causing disease. Immunoassay detection of toxin A and toxin B in stool specimen is commonly used as a diagnostic aid.
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