Parasitology: Cystoisospora belli: 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: Cystoisospora belli

Sample item

A patient with advanced HIV has chronic watery diarrhoea, and a modified acid-fast stain of stool shows large oval oocysts, 20 to 30 micrometres, each with two sporocysts. Which drug is effective?

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

The answer and the reasoning

A. Cotrimoxazole

Cystoisospora belli causes diarrhoea in the immunocompromised and responds to cotrimoxazole. Cryptosporidium oocysts are smaller, about 4 to 6 micrometres. Albendazole acts on helminths and metronidazole on anaerobic protozoa.

Option by option

  • A. Cotrimoxazole (correct)

    Correct. Cotrimoxazole treats Cystoisospora.

  • B. Metronidazole

    Metronidazole is not active against coccidia.

  • C. Nitazoxanide alone

    Nitazoxanide is for Cryptosporidium, which has smaller oocysts.

  • D. Albendazole

    Albendazole is an anthelmintic.

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 A, Cotrimoxazole. Cystoisospora belli causes diarrhoea in the immunocompromised and responds to cotrimoxazole.

Why is "Metronidazole" not the answer?

Metronidazole is not active against coccidia.

Why is "Nitazoxanide alone" not the answer?

Nitazoxanide is for Cryptosporidium, which has smaller oocysts.

Why is "Albendazole" not the answer?

Albendazole is an anthelmintic.

What concept does this question test?

It tests Parasitology: Cystoisospora belli in Microbiology. Cryptosporidium oocysts are smaller, about 4 to 6 micrometres. Albendazole acts on helminths and metronidazole on anaerobic protozoa.

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 Parasitology: Cystoisospora belli?

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.