Which organism is classically associated with rice-water stools?

Which organism is classically associated with rice-water stools?

• A. Vibrio cholerae
• B. Shigella dysenteriae
• C. Escherichia coli
• D. Salmonella enterica

Answer: (A)

Rice-water stools come from a massive secretory diarrhea driven by cholera toxin. Vibrio cholerae releases this toxin, which binds enterocytes in the small intestine and permanently activates the Gs protein, driving a rise in intracellular cAMP. The elevated cAMP keeps chloride channels (like CFTR) open, causing continuous chloride—and thus water and bicarbonate—secretion into the intestinal lumen. The result is large volumes of pale, watery stool with mucus that has the characteristic “rice-water” appearance and often a fishy odor. This pattern of extreme, noninflammatory watery diarrhea is the classic hallmark of cholera. Other bacteria listed can cause diarrhea, but they don’t produce this rice-water stool. Shigella dysenteriae causes inflammatory dysentery with blood and pus; E. coli and Salmonella species can cause watery or inflammatory diarrheas but not the distinctive rice-water stools seen with cholera.

Rice-water stools come from a massive secretory diarrhea driven by cholera toxin. Vibrio cholerae releases this toxin, which binds enterocytes in the small intestine and permanently activates the Gs protein, driving a rise in intracellular cAMP. The elevated cAMP keeps chloride channels (like CFTR) open, causing continuous chloride—and thus water and bicarbonate—secretion into the intestinal lumen. The result is large volumes of pale, watery stool with mucus that has the characteristic “rice-water” appearance and often a fishy odor. This pattern of extreme, noninflammatory watery diarrhea is the classic hallmark of cholera.

Other bacteria listed can cause diarrhea, but they don’t produce this rice-water stool. Shigella dysenteriae causes inflammatory dysentery with blood and pus; E. coli and Salmonella species can cause watery or inflammatory diarrheas but not the distinctive rice-water stools seen with cholera.