Bacterial infections: topical antibiotics: practice question

A Dermatology 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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Dermatology · Bacterial infections: topical antibiotics

Sample item

What is the mechanism of action of topical mupirocin used for impetigo and nasal carriage of Staphylococcus aureus?

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

The answer and the reasoning

D. Inhibition of bacterial isoleucyl-tRNA synthetase

Mupirocin competitively inhibits isoleucyl-tRNA synthetase and so halts protein synthesis. Resistance develops with prolonged use, so courses should be limited to about 5 to 10 days.

Option by option

  • A. Binding to D-Ala-D-Ala to block cell wall synthesis

    D-Ala-D-Ala binding describes vancomycin.

  • B. Binding to the 30S ribosomal subunit

    30S binding describes aminoglycosides and tetracyclines.

  • C. Inhibition of DNA gyrase

    DNA gyrase inhibition describes quinolones.

  • D. Inhibition of bacterial isoleucyl-tRNA synthetase (correct)

    Correct. Isoleucyl-tRNA synthetase inhibition is unique to mupirocin.

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 Dermatology question

What is the answer to this Dermatology question?

The best answer is D, Inhibition of bacterial isoleucyl-tRNA synthetase. Mupirocin competitively inhibits isoleucyl-tRNA synthetase and so halts protein synthesis.

Why is "Binding to D-Ala-D-Ala to block cell wall synthesis" not the answer?

D-Ala-D-Ala binding describes vancomycin.

Why is "Binding to the 30S ribosomal subunit" not the answer?

30S binding describes aminoglycosides and tetracyclines.

Why is "Inhibition of DNA gyrase" not the answer?

DNA gyrase inhibition describes quinolones.

What concept does this question test?

It tests Bacterial infections: topical antibiotics in Dermatology. Resistance develops with prolonged use, so courses should be limited to about 5 to 10 days.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Bacterial infections: topical antibiotics?

Learn each condition by its primary lesion, site and signature sign. Then use the flashcards and the other Dermatology 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.