Bacteriology: Bacillus: 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: Bacillus

Sample item

A wool sorter has a painless black eschar on the forearm with surrounding oedema. Gram stain shows large Gram-positive bacilli in chains. On culture the colonies look like a 'medusa head', and the capsule is composed of D-glutamic acid. What is the organism?

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

The answer and the reasoning

D. Bacillus anthracis

Bacillus anthracis is a non-motile, capsulated, spore-forming bacillus whose polypeptide capsule (poly-D-glutamic acid) resists phagocytosis. Colonies have a 'medusa head' appearance, and it grows as a 'bamboo stick' chain. Cutaneous anthrax causes a painless eschar and is treated with ciprofloxacin or doxycycline.

Option by option

  • A. Clostridium septicum

    Clostridium septicum is an anaerobe that causes gas gangrene.

  • B. Bacillus cereus

    B. cereus is motile and has no capsule, and causes food poisoning.

  • C. Staphylococcus aureus

    Staphylococcus aureus produces cocci in clusters, not bacilli.

  • D. Bacillus anthracis (correct)

    Correct. The polypeptide capsule and medusa-head colonies are characteristic.

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, Bacillus anthracis. Bacillus anthracis is a non-motile, capsulated, spore-forming bacillus whose polypeptide capsule (poly-D-glutamic acid) resists phagocytosis.

Why is "Clostridium septicum" not the answer?

Clostridium septicum is an anaerobe that causes gas gangrene.

Why is "Bacillus cereus" not the answer?

B. cereus is motile and has no capsule, and causes food poisoning.

Why is "Staphylococcus aureus" not the answer?

Staphylococcus aureus produces cocci in clusters, not bacilli.

What concept does this question test?

It tests Bacteriology: Bacillus in Microbiology. Colonies have a 'medusa head' appearance, and it grows as a 'bamboo stick' chain. Cutaneous anthrax causes a painless eschar and is treated with ciprofloxacin or doxycycline.

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: Bacillus?

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.