Bacteriology: anthrax toxin: 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: anthrax toxin

Sample item

A tannery worker has a painless black eschar on the forearm with marked surrounding oedema. In the pathogenesis of this disease, which component of the toxin binds the host cell receptor and forms the pore through which the enzymatic components enter?

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

The answer and the reasoning

D. Protective antigen

Anthrax toxin is a three-part toxin. Protective antigen binds host receptors, is cleaved and forms a heptameric pore that translocates edema factor, a calmodulin-dependent adenylate cyclase, and lethal factor, a zinc metalloprotease that cleaves MAP kinase kinases. The capsule is antiphagocytic and is not part of the toxin.

Option by option

  • A. Lethal factor

    Lethal factor is the enzymatic zinc protease that enters through the pore and causes cell death.

  • B. Edema factor

    Edema factor is the adenylate cyclase that causes oedema once it has entered the cell.

  • C. Poly-D-glutamic acid capsule

    The capsule resists phagocytosis but does not bind receptors or transport toxins.

  • D. Protective antigen (correct)

    Correct. Protective antigen is the binding and translocation component.

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, Protective antigen. Anthrax toxin is a three-part toxin.

Why is "Lethal factor" not the answer?

Lethal factor is the enzymatic zinc protease that enters through the pore and causes cell death.

Why is "Edema factor" not the answer?

Edema factor is the adenylate cyclase that causes oedema once it has entered the cell.

Why is "Poly-D-glutamic acid capsule" not the answer?

The capsule resists phagocytosis but does not bind receptors or transport toxins.

What concept does this question test?

It tests Bacteriology: anthrax toxin in Microbiology. Protective antigen binds host receptors, is cleaved and forms a heptameric pore that translocates edema factor, a calmodulin-dependent adenylate cyclase, and lethal factor, a zinc metalloprotease that cleaves MAP kinase kinases. The capsule is antiphagocytic and is not part of the toxin.

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: anthrax toxin?

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.