Respiratory medicine: Legionella pneumonia: practice question

A General Medicine 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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General Medicine · Respiratory medicine: Legionella pneumonia

Sample item

A 60-year-old smoker returns from a hotel stay with a faulty air-conditioning system. He has high fever, confusion, diarrhoea, relative bradycardia and sodium of 126 mmol/L. Which test is the most appropriate to confirm the cause?

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

The answer and the reasoning

C. Urinary Legionella antigen

Legionella pneumophila causes pneumonia with extrapulmonary features such as hyponatraemia, diarrhoea and confusion. The urinary antigen test detects serogroup 1 and gives rapid diagnosis. Treatment is with a macrolide such as azithromycin or a respiratory fluoroquinolone.

Option by option

  • A. Sputum Ziehl-Neelsen stain

    Ziehl-Neelsen stain is used for tuberculosis, which does not explain the exposure and features.

  • B. Blood culture on routine media alone

    Legionella does not grow on routine media and needs buffered charcoal yeast extract agar.

  • C. Urinary Legionella antigen (correct)

    Correct. Urinary antigen is the quick, standard test for Legionella.

  • D. Cold agglutinin titre

    Cold agglutinins point to Mycoplasma pneumoniae.

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.

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Questions about this General Medicine question

What is the answer to this General Medicine question?

The best answer is C, Urinary Legionella antigen. Legionella pneumophila causes pneumonia with extrapulmonary features such as hyponatraemia, diarrhoea and confusion.

Why is "Sputum Ziehl-Neelsen stain" not the answer?

Ziehl-Neelsen stain is used for tuberculosis, which does not explain the exposure and features.

Why is "Blood culture on routine media alone" not the answer?

Legionella does not grow on routine media and needs buffered charcoal yeast extract agar.

Why is "Cold agglutinin titre" not the answer?

Cold agglutinins point to Mycoplasma pneumoniae.

What concept does this question test?

It tests Respiratory medicine: Legionella pneumonia in General Medicine. The urinary antigen test detects serogroup 1 and gives rapid diagnosis. Treatment is with a macrolide such as azithromycin or a respiratory fluoroquinolone.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Respiratory medicine: Legionella pneumonia?

For each disease know the classic presentation, the best test, and the first-line treatment. Then use the flashcards and the other General Medicine 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.