Antimicrobial resistance: ESBL: 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 · Antimicrobial resistance: ESBL

Sample item

A diabetic ICU patient has Escherichia coli bacteraemia. The isolate is resistant to ceftriaxone, ceftazidime and aztreonam, susceptible to cefoxitin and shows an enlarged inhibition zone toward a clavulanate disk. Which is the most appropriate definitive therapy?

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

The answer and the reasoning

C. Meropenem

Resistance to third-generation cephalosporins and aztreonam, with cefoxitin susceptibility and synergy with clavulanate, indicates an extended-spectrum beta-lactamase producer. Carbapenems are stable to ESBL hydrolysis and are the treatment of choice for serious infection. Piperacillin-tazobactam was inferior to meropenem for ceftriaxone-resistant bloodstream infection in a randomised trial.

Option by option

  • A. High-dose ceftriaxone

    Ceftriaxone is hydrolysed by ESBLs, and a higher dose does not overcome the enzyme.

  • B. Cefepime

    Cefepime is partly hydrolysed by ESBLs, so its activity is unreliable.

  • C. Meropenem (correct)

    Correct. Carbapenems resist hydrolysis by ESBLs.

  • D. Piperacillin-tazobactam

    Piperacillin-tazobactam showed worse outcomes than meropenem in bacteraemia with ceftriaxone-resistant isolates.

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 Microbiology question

What is the answer to this Microbiology question?

The best answer is C, Meropenem. Resistance to third-generation cephalosporins and aztreonam, with cefoxitin susceptibility and synergy with clavulanate, indicates an extended-spectrum beta-lactamase producer.

Why is "High-dose ceftriaxone" not the answer?

Ceftriaxone is hydrolysed by ESBLs, and a higher dose does not overcome the enzyme.

Why is "Cefepime" not the answer?

Cefepime is partly hydrolysed by ESBLs, so its activity is unreliable.

Why is "Piperacillin-tazobactam" not the answer?

Piperacillin-tazobactam showed worse outcomes than meropenem in bacteraemia with ceftriaxone-resistant isolates.

What concept does this question test?

It tests Antimicrobial resistance: ESBL in Microbiology. Carbapenems are stable to ESBL hydrolysis and are the treatment of choice for serious infection. Piperacillin-tazobactam was inferior to meropenem for ceftriaxone-resistant bloodstream infection in a randomised trial.

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 Antimicrobial resistance: ESBL?

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.