Mycology: Coccidioides laboratory hazard: 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 · Mycology: Coccidioides laboratory hazard

Sample item

A laboratory receives a respiratory specimen from a traveller returning from Arizona. A white cottony mould grows on Sabouraud agar, and the technician considers opening the plate on the open bench. Why is this dangerous?

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

The answer and the reasoning

A. The mould phase releases airborne arthroconidia that are highly infectious, so handling needs a biosafety cabinet in a BSL-3 setting

Coccidioides is dimorphic: it forms spherules with endospores in tissue and a mould with barrel-shaped arthroconidia in culture. The arthroconidia become airborne and are infective in very small numbers, so mould cultures are manipulated in a biological safety cabinet under BSL-3 conditions. The patient's respiratory secretions, which contain spherules, are far less hazardous.

Option by option

  • A. The mould phase releases airborne arthroconidia that are highly infectious, so handling needs a biosafety cabinet in a BSL-3 setting (correct)

    Airborne arthroconidia from the mould phase are the hazard and need BSL-3 containment.

  • B. The mould produces aflatoxin that is carcinogenic on inhalation

    Aflatoxin is produced by Aspergillus flavus and is not the hazard of Coccidioides culture.

  • C. The yeast phase at 37 degrees C produces toxins that are absorbed through skin

    The tissue form does not produce skin-absorbed toxins, and laboratory hazard arises from inhaled arthroconidia.

  • D. The plate contains spherules that are transmitted person to person

    Spherules in clinical material are not usually transmitted between people, which is why patients need no isolation.

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 A, The mould phase releases airborne arthroconidia that are highly infectious, so handling needs a biosafety cabinet in a BSL-3 setting. Coccidioides is dimorphic: it forms spherules with endospores in tissue and a mould with barrel-shaped arthroconidia in culture.

Why is "The mould produces aflatoxin that is carcinogenic on inhalation" not the answer?

Aflatoxin is produced by Aspergillus flavus and is not the hazard of Coccidioides culture.

Why is "The yeast phase at 37 degrees C produces toxins that are absorbed thr…" not the answer?

The tissue form does not produce skin-absorbed toxins, and laboratory hazard arises from inhaled arthroconidia.

Why is "The plate contains spherules that are transmitted person to person" not the answer?

Spherules in clinical material are not usually transmitted between people, which is why patients need no isolation.

What concept does this question test?

It tests Mycology: Coccidioides laboratory hazard in Microbiology. The arthroconidia become airborne and are infective in very small numbers, so mould cultures are manipulated in a biological safety cabinet under BSL-3 conditions. The patient's respiratory secretions, which contain spherules, are far less hazardous.

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 Mycology: Coccidioides laboratory hazard?

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.