Antimicrobials: mupirocin mechanism: practice question

A Pharmacology 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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Pharmacology · Antimicrobials: mupirocin mechanism

Sample item

A surgical ward nurse with persistent MRSA colonisation of the anterior nares receives intranasal mupirocin. Which bacterial enzyme does it inhibit?

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

The answer and the reasoning

A. Isoleucyl-tRNA synthetase

Mupirocin binds bacterial isoleucyl-tRNA synthetase, so isoleucine cannot be charged onto tRNA and protein synthesis stops. It is applied topically for impetigo and for eradicating nasal carriage of Staphylococcus aureus. It is not used systemically because it is rapidly inactivated.

Option by option

  • A. Isoleucyl-tRNA synthetase (correct)

    Correct. Mupirocin inhibits isoleucyl-tRNA synthetase.

  • B. DNA gyrase

    DNA gyrase inhibition is the action of fluoroquinolones.

  • C. Peptidoglycan transpeptidase

    Transpeptidase inhibition is the action of beta-lactams.

  • D. Peptidyl transferase on the 50S subunit

    Peptidyl transferase inhibition is the action of chloramphenicol.

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 Pharmacology question

What is the answer to this Pharmacology question?

The best answer is A, Isoleucyl-tRNA synthetase. Mupirocin binds bacterial isoleucyl-tRNA synthetase, so isoleucine cannot be charged onto tRNA and protein synthesis stops.

Why is "DNA gyrase" not the answer?

DNA gyrase inhibition is the action of fluoroquinolones.

Why is "Peptidoglycan transpeptidase" not the answer?

Transpeptidase inhibition is the action of beta-lactams.

Why is "Peptidyl transferase on the 50S subunit" not the answer?

Peptidyl transferase inhibition is the action of chloramphenicol.

What concept does this question test?

It tests Antimicrobials: mupirocin mechanism in Pharmacology. It is applied topically for impetigo and for eradicating nasal carriage of Staphylococcus aureus. It is not used systemically because it is rapidly inactivated.

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 Antimicrobials: mupirocin mechanism?

Learn drugs as classes, then the exception in each class that an examiner would pick. Then use the flashcards and the other Pharmacology 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.