Bacterial toxins: 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 · Bacterial toxins

Sample item

Diphtheria toxin acts by:

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

The answer and the reasoning

B. ADP-ribosylation of elongation factor 2

Diphtheria toxin and Pseudomonas exotoxin A ADP-ribosylate EF-2 and halt protein synthesis. Cell death in the throat produces the grey pseudomembrane.

Option by option

  • A. Cross-linking T-cell receptors and MHC class II as a superantigen

    Toxic shock syndrome toxin is a superantigen.

  • B. ADP-ribosylation of elongation factor 2 (correct)

    Correct.

  • C. Activation of adenylate cyclase through Gs

    That is the mechanism of cholera toxin.

  • D. Cleavage of SNARE proteins

    Tetanus and botulinum toxins cleave SNARE proteins.

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 B, ADP-ribosylation of elongation factor 2. Diphtheria toxin and Pseudomonas exotoxin A ADP-ribosylate EF-2 and halt protein synthesis.

Why is "Cross-linking T-cell receptors and MHC class II as a superantigen" not the answer?

Toxic shock syndrome toxin is a superantigen.

Why is "Activation of adenylate cyclase through Gs" not the answer?

That is the mechanism of cholera toxin.

Why is "Cleavage of SNARE proteins" not the answer?

Tetanus and botulinum toxins cleave SNARE proteins.

What concept does this question test?

It tests Bacterial toxins in Microbiology. Cell death in the throat produces the grey pseudomembrane.

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 Bacterial toxins?

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.