General microbiology: disinfection: 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 · General microbiology: disinfection

Sample item

A bottle of blood from a patient with hepatitis B breaks on the ward floor. After wearing gloves and covering the spill with absorbent material, which disinfectant is appropriate?

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

The answer and the reasoning

D. 1% sodium hypochlorite applied for about 10 minutes

Large blood spills are flooded with 1% sodium hypochlorite (about 10,000 ppm available chlorine) because it inactivates hepatitis B and HIV even in the presence of organic matter. Alcohol evaporates quickly and is inactivated by protein, and chlorhexidine is a skin antiseptic. Lower concentrations such as 0.5% are used for general surfaces.

Option by option

  • A. 0.05% chlorhexidine solution

    Chlorhexidine is intended for skin and has weak activity against viruses.

  • B. 70% ethanol sprayed and wiped immediately

    Alcohol dries before adequate contact time and is poor against organic load.

  • C. Plain soap and water only

    Soap and water clean but do not disinfect a blood spill.

  • D. 1% sodium hypochlorite applied for about 10 minutes (correct)

    Correct. High-concentration hypochlorite penetrates blood and kills bloodborne viruses.

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, 1% sodium hypochlorite applied for about 10 minutes. Large blood spills are flooded with 1% sodium hypochlorite (about 10,000 ppm available chlorine) because it inactivates hepatitis B and HIV even in the presence of organic matter.

Why is "0.05% chlorhexidine solution" not the answer?

Chlorhexidine is intended for skin and has weak activity against viruses.

Why is "70% ethanol sprayed and wiped immediately" not the answer?

Alcohol dries before adequate contact time and is poor against organic load.

Why is "Plain soap and water only" not the answer?

Soap and water clean but do not disinfect a blood spill.

What concept does this question test?

It tests General microbiology: disinfection in Microbiology. Alcohol evaporates quickly and is inactivated by protein, and chlorhexidine is a skin antiseptic. Lower concentrations such as 0.5% are used for general surfaces.

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 General microbiology: disinfection?

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.