Sterilisation: Bowie-Dick test: 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: Bowie-Dick test

Sample item

A central sterile supply department uses a pre-vacuum steam steriliser. Each morning a technician runs a folded-towel test pack with a chemical indicator sheet at 134 degrees C for a short cycle. The indicator shows uniform colour change across the sheet. What does this confirm?

AThat the load will remain sterile for 6 monthsBEffective air removal and steam penetrationCThat all bacterial spores in the load have been killedDThat the chamber reached 160 degrees C

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

The answer and the reasoning

B. Effective air removal and steam penetration

The Bowie-Dick test checks that the vacuum phase of a pre-vacuum autoclave removes air and that steam penetrates a dense pack. Residual air pockets prevent steam contact, so the indicator would show uneven colour change. Sterility of loads is verified by biological indicators such as spores of Geobacillus stearothermophilus and by chemical and physical monitoring of each cycle.

Option by option

A. That the load will remain sterile for 6 months
Shelf life depends on packaging and storage conditions, not on this test.
B. Effective air removal and steam penetration (correct)
Correct. A uniform change indicates complete air removal and steam penetration.
C. That all bacterial spores in the load have been killed
Spore killing is demonstrated by biological indicators, not by this chemical pack.
D. That the chamber reached 160 degrees C
The test does not measure chamber temperature beyond the cycle setting and is not for dry heat.

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.

Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is B, Effective air removal and steam penetration. The Bowie-Dick test checks that the vacuum phase of a pre-vacuum autoclave removes air and that steam penetrates a dense pack.

Why is "That the load will remain sterile for 6 months" not the answer?

Shelf life depends on packaging and storage conditions, not on this test.

Why is "That all bacterial spores in the load have been killed" not the answer?

Spore killing is demonstrated by biological indicators, not by this chemical pack.

Why is "That the chamber reached 160 degrees C" not the answer?

The test does not measure chamber temperature beyond the cycle setting and is not for dry heat.

What concept does this question test?

It tests Sterilisation: Bowie-Dick test in Microbiology. Residual air pockets prevent steam contact, so the indicator would show uneven colour change. Sterility of loads is verified by biological indicators such as spores of Geobacillus stearothermophilus and by chemical and physical monitoring of each cycle.

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: Bowie-Dick test?

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.