Sterilisation: prion decontamination: 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 · Sterilisation: prion decontamination

Sample item

Neurosurgical instruments were used on a patient later diagnosed with sporadic Creutzfeldt-Jakob disease. Which reprocessing method is appropriate for the reusable instruments?

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

The answer and the reasoning

B. Immersion in 1 N sodium hydroxide followed by autoclaving at 134 degrees C for 18 minutes

Prions are abnormally folded proteins that resist routine heat, radiation and most chemical disinfectants. Recommended measures combine a chemical step (1 N sodium hydroxide or concentrated hypochlorite) with prolonged or higher-temperature steam sterilisation, such as 134 degrees C for 18 minutes. Aldehydes cross-link and fix tissue protein, which can actually protect prions.

Option by option

  • A. A 20-minute soak in 2% glutaraldehyde

    Glutaraldehyde fixes proteins and does not inactivate prions; it is suited to heat-sensitive endoscopes.

  • B. Immersion in 1 N sodium hydroxide followed by autoclaving at 134 degrees C for 18 minutes (correct)

    Correct. Alkali degrades prion protein and high-temperature steam completes the inactivation.

  • C. Exposure to ethylene oxide gas for one cycle

    Ethylene oxide is a gaseous alkylating agent that is not reliably prion-inactivating; it is used for heat-sensitive plastics.

  • D. A standard autoclave cycle at 121 degrees C for 15 minutes alone

    A routine cycle is not enough because prions survive 121 degrees C for 15 minutes.

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, Immersion in 1 N sodium hydroxide followed by autoclaving at 134 degrees C for 18 minutes. Prions are abnormally folded proteins that resist routine heat, radiation and most chemical disinfectants.

Why is "A 20-minute soak in 2% glutaraldehyde" not the answer?

Glutaraldehyde fixes proteins and does not inactivate prions; it is suited to heat-sensitive endoscopes.

Why is "Exposure to ethylene oxide gas for one cycle" not the answer?

Ethylene oxide is a gaseous alkylating agent that is not reliably prion-inactivating; it is used for heat-sensitive plastics.

Why is "A standard autoclave cycle at 121 degrees C for 15 minutes alone" not the answer?

A routine cycle is not enough because prions survive 121 degrees C for 15 minutes.

What concept does this question test?

It tests Sterilisation: prion decontamination in Microbiology. Recommended measures combine a chemical step (1 N sodium hydroxide or concentrated hypochlorite) with prolonged or higher-temperature steam sterilisation, such as 134 degrees C for 18 minutes. Aldehydes cross-link and fix tissue protein, which can actually protect prions.

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 Sterilisation: prion decontamination?

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.