Antimicrobials: mechanisms of resistance: 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: mechanisms of resistance

Sample item

A bacterium becomes resistant to penicillins by producing an enzyme that hydrolyses the beta-lactam ring. Which resistance mechanism is this?

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

The answer and the reasoning

D. Enzymatic inactivation by beta-lactamase

Beta-lactamases cleave the beta-lactam ring and are the main mechanism of resistance in many gram-negative and staphylococcal strains, and they are countered by inhibitors such as clavulanate. MRSA resistance is due to altered PBP2a instead.

Option by option

  • A. Efflux pump upregulation

    Efflux describes tetracycline and fluoroquinolone resistance.

  • B. Altered target binding protein

    Altered PBPs describe MRSA, a different mechanism.

  • C. Reduced porin permeability

    Porin loss reduces entry and is a different mechanism.

  • D. Enzymatic inactivation by beta-lactamase (correct)

    Correct. Enzymatic hydrolysis by beta-lactamase.

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 D, Enzymatic inactivation by beta-lactamase. Beta-lactamases cleave the beta-lactam ring and are the main mechanism of resistance in many gram-negative and staphylococcal strains, and they are countered by inhibitors such as clavulanate.

Why is "Efflux pump upregulation" not the answer?

Efflux describes tetracycline and fluoroquinolone resistance.

Why is "Altered target binding protein" not the answer?

Altered PBPs describe MRSA, a different mechanism.

Why is "Reduced porin permeability" not the answer?

Porin loss reduces entry and is a different mechanism.

What concept does this question test?

It tests Antimicrobials: mechanisms of resistance in Pharmacology. MRSA resistance is due to altered PBP2a instead.

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: mechanisms of resistance?

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.