Bacteriology: Stenotrophomonas maltophilia treatment: 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.

Try it

Microbiology · Bacteriology: Stenotrophomonas maltophilia treatment

Sample item

A ventilated ICU patient treated with meropenem for 10 days develops new pneumonia. Sputum grows an oxidase-negative, non-fermenting Gram-negative bacillus that is resistant to meropenem. Which drug is a first-line choice for this organism?

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

The answer and the reasoning

D. Trimethoprim-sulfamethoxazole

Stenotrophomonas maltophilia is intrinsically resistant to carbapenems because of a chromosomal metallo-beta-lactamase, and it also resists aztreonam and aminoglycosides. Trimethoprim-sulfamethoxazole is the drug of choice, and carbapenem exposure is a recognised risk factor.

Option by option

  • A. Imipenem-cilastatin

    Imipenem is hydrolysed by the organism's intrinsic metallo-beta-lactamase.

  • B. Gentamicin

    Aminoglycosides are poorly active because of low permeability and efflux.

  • C. Aztreonam

    Aztreonam is inactivated by another chromosomal beta-lactamase and is not effective.

  • D. Trimethoprim-sulfamethoxazole (correct)

    Correct. This combination is the first-line agent for the organism.

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, Trimethoprim-sulfamethoxazole. Stenotrophomonas maltophilia is intrinsically resistant to carbapenems because of a chromosomal metallo-beta-lactamase, and it also resists aztreonam and aminoglycosides.

Why is "Imipenem-cilastatin" not the answer?

Imipenem is hydrolysed by the organism's intrinsic metallo-beta-lactamase.

Why is "Gentamicin" not the answer?

Aminoglycosides are poorly active because of low permeability and efflux.

Why is "Aztreonam" not the answer?

Aztreonam is inactivated by another chromosomal beta-lactamase and is not effective.

What concept does this question test?

It tests Bacteriology: Stenotrophomonas maltophilia treatment in Microbiology. Trimethoprim-sulfamethoxazole is the drug of choice, and carbapenem exposure is a recognised risk factor.

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 Bacteriology: Stenotrophomonas maltophilia treatment?

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.