Clinical Significance

After treatment with antibiotics, many patients develop gastrointestinal symptoms ranging from mild diarrhea to severe pseudomembranous colitis. Many cases of the milder forms of gastrointestinal illness and most cases of pseudomembranous colitis are caused by toxigenic strains of Clostridioides (Clostridium) difficile. This organism is an opportunistic anaerobic bacterium that grows in the intestine once the normal flora has been altered by the antibiotic. Toxigenic strains of C. difficile carry the genes encoding the toxins while non-toxigenic strains do not carry the toxin genes. Disease onset is associated with the toxins that are produced by the toxigenic organism. The clinical symptoms associated with the disease are believed to be primarily due to toxin A, which is a tissue-damaging enterotoxin. C. difficile also produces a second toxin designated toxin B. Toxin B which has been referred to as cytotoxin is detected by tissue-damaging enterotoxin. C. difficile is a good antigen marker for the organism in feces because it is produces in high amounts by all strains, toxigenic or non toxigenic.