Community dentistry: biological monitoring of autoclaves: practice question

A Dentistry 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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Dentistry · Community dentistry: biological monitoring of autoclaves

Sample item

Which organism's spores are used as the biological indicator for monitoring steam autoclave sterilisation in a dental clinic?

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

The answer and the reasoning

C. Geobacillus stearothermophilus

Spores of Geobacillus (Bacillus) stearothermophilus are highly resistant to moist heat, so their failure to grow after a cycle shows the autoclave is working. Spores of Bacillus atrophaeus (subtilis var. niger) are used for dry heat and ethylene oxide. Vegetative bacteria are not resistant enough to be suitable.

Option by option

  • A. Clostridium tetani

    Clostridium tetani is a pathogen and is not used for routine monitoring.

  • B. Bacillus subtilis var. niger

    Bacillus subtilis var. niger spores are used for dry heat and ethylene oxide.

  • C. Geobacillus stearothermophilus (correct)

    Correct. Its heat-resistant spores monitor steam sterilisation.

  • D. Staphylococcus aureus

    Staphylococcus aureus is a vegetative organism killed easily by heat, so it is not a suitable 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 Dentistry question

What is the answer to this Dentistry question?

The best answer is C, Geobacillus stearothermophilus. Spores of Geobacillus (Bacillus) stearothermophilus are highly resistant to moist heat, so their failure to grow after a cycle shows the autoclave is working.

Why is "Clostridium tetani" not the answer?

Clostridium tetani is a pathogen and is not used for routine monitoring.

Why is "Bacillus subtilis var. niger" not the answer?

Bacillus subtilis var. niger spores are used for dry heat and ethylene oxide.

Why is "Staphylococcus aureus" not the answer?

Staphylococcus aureus is a vegetative organism killed easily by heat, so it is not a suitable indicator.

What concept does this question test?

It tests Community dentistry: biological monitoring of autoclaves in Dentistry. Spores of Bacillus atrophaeus (subtilis var. niger) are used for dry heat and ethylene oxide. Vegetative bacteria are not resistant enough to be suitable.

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 Community dentistry: biological monitoring of autoclaves?

Learn the dental formula, eruption ages and tooth structure once, as tables. Then use the flashcards and the other Dentistry 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.