Coccidian parasites: Cyclospora: 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 · Coccidian parasites: Cyclospora

Sample item

A traveller returning from Nepal has prolonged relapsing watery diarrhoea and fatigue after eating fresh raspberries. A modified acid-fast stool smear shows variably stained round oocysts about 8 to 10 micrometres across that autofluoresce under UV light. Which organism and treatment fit?

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

The answer and the reasoning

B. Cyclospora cayetanensis, treated with trimethoprim-sulfamethoxazole

Cyclospora oocysts are 8 to 10 micrometres, variably acid-fast and autofluorescent under UV light. Infection is linked to imported fresh produce, and trimethoprim-sulfamethoxazole is the drug of choice. Cryptosporidium oocysts are smaller, at 4 to 6 micrometres.

Option by option

  • A. Entamoeba histolytica, treated with fluconazole

    Entamoeba histolytica is an amoeba, and fluconazole is an antifungal with no role here.

  • B. Cyclospora cayetanensis, treated with trimethoprim-sulfamethoxazole (correct)

    Correct. Size, variable acid-fastness, autofluorescence and the exposure fit Cyclospora, which responds to co-trimoxazole.

  • C. Cryptosporidium parvum, treated with metronidazole

    Cryptosporidium oocysts are about 4 to 6 micrometres, uniformly acid-fast and do not respond to metronidazole.

  • D. Giardia lamblia, treated with albendazole alone

    Giardia is diagnosed by cysts or trophozoites and is not acid-fast, and albendazole alone is not standard therapy.

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 B, Cyclospora cayetanensis, treated with trimethoprim-sulfamethoxazole. Cyclospora oocysts are 8 to 10 micrometres, variably acid-fast and autofluorescent under UV light.

Why is "Entamoeba histolytica, treated with fluconazole" not the answer?

Entamoeba histolytica is an amoeba, and fluconazole is an antifungal with no role here.

Why is "Cryptosporidium parvum, treated with metronidazole" not the answer?

Cryptosporidium oocysts are about 4 to 6 micrometres, uniformly acid-fast and do not respond to metronidazole.

Why is "Giardia lamblia, treated with albendazole alone" not the answer?

Giardia is diagnosed by cysts or trophozoites and is not acid-fast, and albendazole alone is not standard therapy.

What concept does this question test?

It tests Coccidian parasites: Cyclospora in Microbiology. Infection is linked to imported fresh produce, and trimethoprim-sulfamethoxazole is the drug of choice. Cryptosporidium oocysts are smaller, at 4 to 6 micrometres.

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 Coccidian parasites: Cyclospora?

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.