Question

An 18 year old girl presents with watery diarrhea. The most likely causative agent is?

• A. Rotavirus
• B. V. cholerae
• C. Salmonella
• D. Shigella

Hint:

Watery stool in an adult, not an infant, favours the rice water toxin producer over rotavirus.

Answer 1

The Correct Option is B

Step 1: The key is the description of the stool. The patient has watery (non-bloody, non-inflammatory) diarrhea, which points to a secretory or enterotoxin-mediated process rather than an invasive one.

Step 2: Among the options, the two organisms that classically cause profuse watery diarrhea are Rotavirus and Vibrio cholerae. The patient is an 18 year old, that is an adult, not an infant. Rotavirus is the most common cause of watery diarrhea in infants and young children, so it is less likely here.

Step 3: Vibrio cholerae produces an enterotoxin that drives massive secretory watery diarrhea (rice water stools) and is the most fitting answer for an adult with watery diarrhea. Hence option b is correct.

Step 4: Salmonella and Shigella typically cause inflammatory or dysenteric illness with fever, blood or mucus in the stool, which does not match a purely watery picture. Therefore V. cholerae is the most likely agent.