Bacteriology: Pasteurella multocida: 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 · Bacteriology: Pasteurella multocida

Sample item

A 40-year-old woman is bitten on the hand by a cat. Within 12 hours the hand is swollen, red and very painful with purulent discharge. Gram stain shows small Gram-negative coccobacilli, and the isolate is oxidase positive and does not grow on MacConkey agar. Which antibiotic is most appropriate?

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

The answer and the reasoning

A. Amoxicillin-clavulanate

Pasteurella multocida is part of the oral flora of cats and dogs and causes rapidly developing cellulitis after bites, usually within 24 hours. It is sensitive to penicillins, and amoxicillin-clavulanate is the usual choice for bite wounds because it also covers anaerobes and staphylococci. Cloxacillin and clindamycin are poorly active against it.

Option by option

  • A. Amoxicillin-clavulanate (correct)

    Amoxicillin-clavulanate covers Pasteurella along with the other bite-wound flora.

  • B. Metronidazole alone

    Metronidazole acts only on anaerobes and has no useful activity against Pasteurella, a facultative organism.

  • C. Cloxacillin

    Cloxacillin has poor activity against Gram-negative Pasteurella.

  • D. Clindamycin alone

    Clindamycin alone does not cover Pasteurella.

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 A, Amoxicillin-clavulanate. Pasteurella multocida is part of the oral flora of cats and dogs and causes rapidly developing cellulitis after bites, usually within 24 hours.

Why is "Metronidazole alone" not the answer?

Metronidazole acts only on anaerobes and has no useful activity against Pasteurella, a facultative organism.

Why is "Cloxacillin" not the answer?

Cloxacillin has poor activity against Gram-negative Pasteurella.

Why is "Clindamycin alone" not the answer?

Clindamycin alone does not cover Pasteurella.

What concept does this question test?

It tests Bacteriology: Pasteurella multocida in Microbiology. It is sensitive to penicillins, and amoxicillin-clavulanate is the usual choice for bite wounds because it also covers anaerobes and staphylococci. Cloxacillin and clindamycin are poorly active against it.

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: Pasteurella multocida?

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.