Bacteriology: practice question

A Microbiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Microbiology · Bacteriology

Sample item

A patient has profuse painless watery 'rice-water' stools and rapid dehydration. The causative organism is a:

AGram-positive coccus in chainsBProtozoan trophozoite containing red blood cellsCCurved Gram-negative bacillusDNon-lactose fermenting, non-motile Gram-negative bacillus

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Curved Gram-negative bacillus

Vibrio cholerae is a comma-shaped, motile Gram-negative bacillus. Cholera toxin activates adenylate cyclase through Gs, raises cAMP and causes massive chloride and water secretion.

Option by option

A. Gram-positive coccus in chains
Streptococci do not cause this syndrome.
B. Protozoan trophozoite containing red blood cells
Entamoeba histolytica causes amoebic dysentery, with ingested red cells in trophozoites.
C. Curved Gram-negative bacillus (correct)
Correct.
D. Non-lactose fermenting, non-motile Gram-negative bacillus
That description fits Shigella, which causes dysentery with blood and mucus.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is C, Curved Gram-negative bacillus. Vibrio cholerae is a comma-shaped, motile Gram-negative bacillus.

Why is "Gram-positive coccus in chains" not the answer?

Streptococci do not cause this syndrome.

Why is "Protozoan trophozoite containing red blood cells" not the answer?

Entamoeba histolytica causes amoebic dysentery, with ingested red cells in trophozoites.

Why is "Non-lactose fermenting, non-motile Gram-negative bacillus" not the answer?

That description fits Shigella, which causes dysentery with blood and mucus.

What concept does this question test?

It tests Bacteriology in Microbiology. Cholera toxin activates adenylate cyclase through Gs, raises cAMP and causes massive chloride and water secretion.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Bacteriology?

Make a one-line identity card for each organism: shape and stain, defining test, toxin, disease and drug. Then use the flashcards and the other Microbiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.