Sterilisation: ionising radiation: 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: ionising radiation

Sample item

A manufacturer wants to sterilise sealed, pre-packed disposable plastic syringes and catheters, which would melt in heat. Which method is commonly used on an industrial scale?

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

The answer and the reasoning

D. Gamma irradiation

Gamma rays are ionising radiation that penetrate packaging and damage microbial DNA, and they are called cold sterilisation because no heat is generated. They are used for disposable plastics, sutures, catheters and some pharmaceuticals. Ultraviolet light is non-ionising and has poor penetrating power.

Option by option

  • A. Boiling for 30 minutes

    Boiling does not kill spores, so it disinfects rather than sterilises, and it cannot treat sealed packs.

  • B. Ultraviolet radiation

    Ultraviolet light does not penetrate packaging and is used only for surfaces and air.

  • C. Hot air oven at 160 degrees C

    A hot air oven at 160 degrees C would melt plastic syringes.

  • D. Gamma irradiation (correct)

    Penetrating gamma rays sterilise sealed heat-labile plastic items without heating them.

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 D, Gamma irradiation. Gamma rays are ionising radiation that penetrate packaging and damage microbial DNA, and they are called cold sterilisation because no heat is generated.

Why is "Boiling for 30 minutes" not the answer?

Boiling does not kill spores, so it disinfects rather than sterilises, and it cannot treat sealed packs.

Why is "Ultraviolet radiation" not the answer?

Ultraviolet light does not penetrate packaging and is used only for surfaces and air.

Why is "Hot air oven at 160 degrees C" not the answer?

A hot air oven at 160 degrees C would melt plastic syringes.

What concept does this question test?

It tests Sterilisation: ionising radiation in Microbiology. They are used for disposable plastics, sutures, catheters and some pharmaceuticals. Ultraviolet light is non-ionising and has poor penetrating power.

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: ionising radiation?

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.