Bacteriology: Moraxella catarrhalis: 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: Moraxella catarrhalis

Sample item

A 65-year-old with COPD has an acute exacerbation. Sputum Gram stain shows kidney-bean shaped Gram-negative diplococci. The isolate is oxidase positive, produces beta-lactamase and ferments no sugars. Which organism is it?

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

The answer and the reasoning

D. Moraxella catarrhalis

Moraxella catarrhalis is an oxidase-positive Gram-negative diplococcus that does not ferment sugars, is usually beta-lactamase positive and causes otitis media, sinusitis and COPD exacerbations. Neisseria species can be separated from it by their sugar fermentation.

Option by option

  • A. Neisseria meningitidis

    N. meningitidis ferments glucose and maltose.

  • B. Haemophilus influenzae

    H. influenzae is a coccobacillus needing X and V factors, not a diplococcus.

  • C. Acinetobacter baumannii

    A. baumannii is an oxidase-negative coccobacillus linked to ventilator-associated pneumonia.

  • D. Moraxella catarrhalis (correct)

    Correct. A non-saccharolytic oxidase-positive diplococcus with beta-lactamase is M. catarrhalis.

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 D, Moraxella catarrhalis. Moraxella catarrhalis is an oxidase-positive Gram-negative diplococcus that does not ferment sugars, is usually beta-lactamase positive and causes otitis media, sinusitis and COPD exacerbations.

Why is "Neisseria meningitidis" not the answer?

N. meningitidis ferments glucose and maltose.

Why is "Haemophilus influenzae" not the answer?

H. influenzae is a coccobacillus needing X and V factors, not a diplococcus.

Why is "Acinetobacter baumannii" not the answer?

A. baumannii is an oxidase-negative coccobacillus linked to ventilator-associated pneumonia.

What concept does this question test?

It tests Bacteriology: Moraxella catarrhalis in Microbiology. Neisseria species can be separated from it by their sugar fermentation.

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 Bacteriology: Moraxella catarrhalis?

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.