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 man develops pneumonia with diarrhoea and hyponatraemia after staying in a hotel with a contaminated air-conditioning cooling tower. Which investigation is the most practical for rapid diagnosis?

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

The answer and the reasoning

B. Urinary antigen test for Legionella pneumophila serogroup 1

Legionnaires' disease follows inhalation of aerosolised water containing Legionella. Organisms stain poorly on Gram stain and do not grow on routine media, needing buffered charcoal yeast extract agar. The urinary antigen test detects serogroup 1 rapidly.

Option by option

  • A. Blood culture on routine blood agar

    Routine blood agar does not support growth because the organism needs cysteine and iron.

  • B. Urinary antigen test for Legionella pneumophila serogroup 1 (correct)

    Correct. Urinary antigen detection is quick and widely used.

  • C. Sputum Gram stain showing numerous Gram-negative rods

    Legionella stains poorly with Gram stain, so this is unreliable.

  • D. Sputum acid-fast stain

    Legionella is not acid-fast, so this stain is not useful.

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.

More Microbiology questions

Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is B, Urinary antigen test for Legionella pneumophila serogroup 1. Legionnaires' disease follows inhalation of aerosolised water containing Legionella.

Why is "Blood culture on routine blood agar" not the answer?

Routine blood agar does not support growth because the organism needs cysteine and iron.

Why is "Sputum Gram stain showing numerous Gram-negative rods" not the answer?

Legionella stains poorly with Gram stain, so this is unreliable.

Why is "Sputum acid-fast stain" not the answer?

Legionella is not acid-fast, so this stain is not useful.

What concept does this question test?

It tests Bacteriology in Microbiology. Organisms stain poorly on Gram stain and do not grow on routine media, needing buffered charcoal yeast extract agar. The urinary antigen test detects serogroup 1 rapidly.

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.