Bacteriology: toxic shock syndrome 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: toxic shock syndrome toxin

Sample item

A 22-year-old woman using a high-absorbency tampon develops fever of 39.5 degrees C, hypotension, diffuse macular erythroderma and, a week later, desquamation of the palms. Which mechanism explains the massive cytokine release?

ACleavage of desmoglein 1 by an exfoliative toxinBA superantigen links MHC class II to the T-cell receptor Vbeta region, activating many T cellsCActivation of TLR4 by lipopolysaccharideDADP-ribosylation of elongation factor 2 in host cells

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

The answer and the reasoning

B. A superantigen links MHC class II to the T-cell receptor Vbeta region, activating many T cells

Toxic shock syndrome toxin-1 of Staphylococcus aureus is a superantigen that cross-links MHC class II on antigen-presenting cells with the Vbeta region of many T-cell receptors, activating up to 20% of T cells and causing a cytokine storm with IL-2, TNF and IFN-gamma. Treatment includes removing the tampon, resuscitation, an anti-staphylococcal drug and clindamycin to suppress toxin production.

Option by option

A. Cleavage of desmoglein 1 by an exfoliative toxin
Desmoglein 1 cleavage by exfoliative toxin causes staphylococcal scalded skin syndrome, with sloughing and no shock.
B. A superantigen links MHC class II to the T-cell receptor Vbeta region, activating many T cells (correct)
Correct. Polyclonal T-cell activation by the superantigen produces shock and the rash.
C. Activation of TLR4 by lipopolysaccharide
LPS acting through TLR4 explains Gram-negative endotoxic shock, not this Gram-positive toxin-mediated syndrome.
D. ADP-ribosylation of elongation factor 2 in host cells
ADP-ribosylation of elongation factor 2 is the mechanism of diphtheria toxin and Pseudomonas exotoxin A.

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.

Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is B, A superantigen links MHC class II to the T-cell receptor Vbeta region, activating many T cells. Toxic shock syndrome toxin-1 of Staphylococcus aureus is a superantigen that cross-links MHC class II on antigen-presenting cells with the Vbeta region of many T-cell receptors, activating up to 20% of T cells and causing a cytokine storm with IL-2, TNF and IFN-gamma.

Why is "Cleavage of desmoglein 1 by an exfoliative toxin" not the answer?

Desmoglein 1 cleavage by exfoliative toxin causes staphylococcal scalded skin syndrome, with sloughing and no shock.

Why is "Activation of TLR4 by lipopolysaccharide" not the answer?

LPS acting through TLR4 explains Gram-negative endotoxic shock, not this Gram-positive toxin-mediated syndrome.

Why is "ADP-ribosylation of elongation factor 2 in host cells" not the answer?

ADP-ribosylation of elongation factor 2 is the mechanism of diphtheria toxin and Pseudomonas exotoxin A.

What concept does this question test?

It tests Bacteriology: toxic shock syndrome toxin in Microbiology. Treatment includes removing the tampon, resuscitation, an anti-staphylococcal drug and clindamycin to suppress toxin production.

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: toxic shock syndrome 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.