Perioperative care: biological indicator for steam sterilisation: practice question

A General Surgery 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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General Surgery · Perioperative care: biological indicator for steam sterilisation

Sample item

A theatre sterilisation unit places spore strips in each autoclave load to confirm that steam sterilisation has worked. Which organism's spores are used as the indicator?

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

The answer and the reasoning

A. Geobacillus stearothermophilus

Spores of Geobacillus stearothermophilus resist steam at autoclave temperatures and are used as the biological indicator, with failure of growth after incubation showing a successful cycle. Bacillus atrophaeus spores are used for ethylene oxide and dry heat.

Option by option

  • A. Geobacillus stearothermophilus (correct)

    Correct. Geobacillus stearothermophilus spores are the standard indicator for steam sterilisation.

  • B. Bacillus atrophaeus

    Bacillus atrophaeus spores are the indicator for ethylene oxide and dry heat sterilisation.

  • C. Staphylococcus aureus

    Staphylococcus aureus is a non-sporing organism and not a sterilisation indicator.

  • D. Clostridium tetani

    Clostridium tetani is a pathogen and not used as a routine indicator.

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 General Surgery question

What is the answer to this General Surgery question?

The best answer is A, Geobacillus stearothermophilus. Spores of Geobacillus stearothermophilus resist steam at autoclave temperatures and are used as the biological indicator, with failure of growth after incubation showing a successful cycle.

Why is "Bacillus atrophaeus" not the answer?

Bacillus atrophaeus spores are the indicator for ethylene oxide and dry heat sterilisation.

Why is "Staphylococcus aureus" not the answer?

Staphylococcus aureus is a non-sporing organism and not a sterilisation indicator.

Why is "Clostridium tetani" not the answer?

Clostridium tetani is a pathogen and not used as a routine indicator.

What concept does this question test?

It tests Perioperative care: biological indicator for steam sterilisation in General Surgery. Bacillus atrophaeus spores are used for ethylene oxide and dry heat.

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 Perioperative care: biological indicator for steam sterilisation?

Learn classic signs and eponyms alongside what they diagnose. Then use the flashcards and the other General Surgery 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.