Question:medium
An 18 year old girl presents with watery diarrhea. The most likely causative agent is?
An 18 year old girl presents with watery diarrhea. The most likely causative agent is?
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Watery stool in an adult, not an infant, favours the rice water toxin producer over rotavirus.
Updated On: Jun 24, 2026
- Rotavirus
- V. cholerae
- Salmonella
- Shigella
Show Solution
The Correct Option is B
Solution and Explanation
Step 1: Diarrhoea questions hinge on whether the stool is watery (secretory) or bloody (invasive). Here the stool is plainly watery, so we steer toward toxin-driven organisms.
Step 2: Two of the listed bugs fit a watery pattern, namely rotavirus and Vibrio cholerae. Age then breaks the tie. Rotavirus dominates watery diarrhoea in infants and toddlers, but our patient is 18 years old, well past that group, so rotavirus slips down the list.
Step 3: That leaves Vibrio cholerae, whose cholera toxin floods the gut with fluid and gives the hallmark rice water stools in adults. It is therefore the best single fit, option b.
Step 4: Salmonella and Shigella belong to the bloody, febrile, dysentery category and clash with a clean watery story, so they are excluded.
\[\boxed{\text{V. cholerae}}\]
Step 2: Two of the listed bugs fit a watery pattern, namely rotavirus and Vibrio cholerae. Age then breaks the tie. Rotavirus dominates watery diarrhoea in infants and toddlers, but our patient is 18 years old, well past that group, so rotavirus slips down the list.
Step 3: That leaves Vibrio cholerae, whose cholera toxin floods the gut with fluid and gives the hallmark rice water stools in adults. It is therefore the best single fit, option b.
Step 4: Salmonella and Shigella belong to the bloody, febrile, dysentery category and clash with a clean watery story, so they are excluded.
\[\boxed{\text{V. cholerae}}\]
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