Bacteriology: Tropheryma whipplei: 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: Tropheryma whipplei

Sample item

A 45-year-old farmer has chronic diarrhoea with steatorrhoea, weight loss and migratory arthralgia for a year. Small bowel biopsy shows foamy macrophages in the lamina propria that are PAS positive and diastase resistant, and Ziehl-Neelsen stain is negative. Which organism is responsible?

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

The answer and the reasoning

C. Tropheryma whipplei

Whipple disease is a multisystem infection by the Gram-positive actinobacterium Tropheryma whipplei. Macrophages in the small bowel mucosa are packed with PAS-positive, acid-fast-negative bacilli, and treatment is prolonged, beginning with ceftriaxone.

Option by option

  • A. Mycobacterium avium complex

    M. avium complex also fills macrophages but the organisms are acid-fast positive.

  • B. Giardia duodenalis

    Giardia is seen as trophozoites on the mucosal surface and not within macrophages.

  • C. Tropheryma whipplei (correct)

    Correct. PAS-positive, acid-fast-negative foamy macrophages indicate Whipple disease.

  • D. Cryptosporidium parvum

    Cryptosporidium sits at the brush border of enterocytes and not inside macrophages.

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 Microbiology question

What is the answer to this Microbiology question?

The best answer is C, Tropheryma whipplei. Whipple disease is a multisystem infection by the Gram-positive actinobacterium Tropheryma whipplei.

Why is "Mycobacterium avium complex" not the answer?

M. avium complex also fills macrophages but the organisms are acid-fast positive.

Why is "Giardia duodenalis" not the answer?

Giardia is seen as trophozoites on the mucosal surface and not within macrophages.

Why is "Cryptosporidium parvum" not the answer?

Cryptosporidium sits at the brush border of enterocytes and not inside macrophages.

What concept does this question test?

It tests Bacteriology: Tropheryma whipplei in Microbiology. Macrophages in the small bowel mucosa are packed with PAS-positive, acid-fast-negative bacilli, and treatment is prolonged, beginning with ceftriaxone.

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: Tropheryma whipplei?

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.