Pseudomembranous colitis is most closely associated with infection by which organism?

Pseudomembranous colitis is most closely associated with infection by which organism?

• A. Clostridium difficile
• B. Staphylococcus aureus
• C. Escherichia coli O157:H7
• D. Clostridium perfringens

Answer: (A)

Pseudomembranous colitis arises when Clostridioides difficile overgrows in the colon after antibiotic use. The organism produces toxins that damage the colonic mucosa and trigger an inflammatory exudate, leading to the characteristic pseudomembranes composed of fibrin, mucus, inflammatory cells, and necrotic debris. This is the classic association with antibiotic-associated diarrhea. Other organisms listed can cause diarrhea or enteritis, but they do not typically produce the pseudomembranes seen in C. difficile infection: Staphylococcus aureus can cause toxin-mediated GI illness but not the same pseudomembranous colitis pattern; Escherichia coli O157:H7 causes hemorrhagic colitis with bloody diarrhea; Clostridium perfringens causes food poisoning from its enterotoxin but not pseudomembrane formation in the colon.

Pseudomembranous colitis arises when Clostridioides difficile overgrows in the colon after antibiotic use. The organism produces toxins that damage the colonic mucosa and trigger an inflammatory exudate, leading to the characteristic pseudomembranes composed of fibrin, mucus, inflammatory cells, and necrotic debris. This is the classic association with antibiotic-associated diarrhea. Other organisms listed can cause diarrhea or enteritis, but they do not typically produce the pseudomembranes seen in C. difficile infection: Staphylococcus aureus can cause toxin-mediated GI illness but not the same pseudomembranous colitis pattern; Escherichia coli O157:H7 causes hemorrhagic colitis with bloody diarrhea; Clostridium perfringens causes food poisoning from its enterotoxin but not pseudomembrane formation in the colon.