Which organism is the primary cause of cholera, presenting with watery diarrhea and dehydration?

• A. Vibrio cholerae
• B. Clostridium difficile
• C. Campylobacter jejuni
• D. Staphylococcus aureus

Answer: (A)

Cholera is caused by a toxin-driven secretory diarrheal illness. The organism Vibrio cholerae is a curved, Gram-negative rod that colonizes the small intestine and produces cholera toxin. This toxin activates adenylate cyclase via ADP-ribosylation of the Gs protein, causing massive chloride and water efflux into the intestinal lumen, leading to profuse watery diarrhea with dehydration—classically described as rice-water stools. Because the pathogen does not invade the intestinal mucosa, stool typically lacks inflammatory cells. Transmission is usually through contaminated water, and treatment hinges on rapid rehydration and electrolyte replacement; antibiotics can help shorten the illness. Other organisms listed cause different problems: Clostridium difficile leads to antibiotic-associated colitis with inflammation; Campylobacter jejuni causes inflammatory or bloody diarrhea; Staphylococcus aureus causes food poisoning with vomiting from preformed toxins.