Parasitology: microsporidia: 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 · Parasitology: microsporidia

Sample item

A patient with AIDS has chronic diarrhoea. A stool smear stained with modified trichrome shows tiny oval spores of 1 to 3 micrometres, each with a belt-like stripe. The organism has a coiled polar tube for host cell invasion. Which organism is it?

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

The answer and the reasoning

C. Enterocytozoon bieneusi

Microsporidia such as Enterocytozoon bieneusi are obligate intracellular fungi-related organisms that cause chronic diarrhoea in advanced HIV. The spores are small and have a polar tube, and they are best seen with modified trichrome or chromotrope stains.

Option by option

  • A. Cystoisospora belli

    Cystoisospora has large acid-fast oocysts of about 25 micrometres.

  • B. Cryptosporidium parvum

    Cryptosporidium oocysts are 4 to 6 micrometres and acid-fast.

  • C. Enterocytozoon bieneusi (correct)

    Correct. Tiny trichrome-stained spores with a polar tube are microsporidia.

  • D. Giardia duodenalis

    Giardia has pear-shaped trophozoites with a sucking disc and oval cysts of 8 to 12 micrometres.

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, Enterocytozoon bieneusi. Microsporidia such as Enterocytozoon bieneusi are obligate intracellular fungi-related organisms that cause chronic diarrhoea in advanced HIV.

Why is "Cystoisospora belli" not the answer?

Cystoisospora has large acid-fast oocysts of about 25 micrometres.

Why is "Cryptosporidium parvum" not the answer?

Cryptosporidium oocysts are 4 to 6 micrometres and acid-fast.

Why is "Giardia duodenalis" not the answer?

Giardia has pear-shaped trophozoites with a sucking disc and oval cysts of 8 to 12 micrometres.

What concept does this question test?

It tests Parasitology: microsporidia in Microbiology. The spores are small and have a polar tube, and they are best seen with modified trichrome or chromotrope stains.

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 Parasitology: microsporidia?

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.