Bacteriology: Jarisch-Herxheimer reaction: 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: Jarisch-Herxheimer reaction

Sample item

Four hours after the first injection of benzathine penicillin for secondary syphilis, a man develops fever with chills, headache, myalgia and intensification of his rash. There is no urticaria, wheeze or hypotension. What is the most likely mechanism?

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

The answer and the reasoning

D. Cytokine release after spirochaete killing

The Jarisch-Herxheimer reaction follows rapid killing of spirochaetes, releasing lipoproteins that trigger TNF-alpha, interleukin 6 and interleukin 8. It occurs within hours, settles in 24 hours and is not an allergy, so penicillin should be continued.

Option by option

  • A. IgE-mediated penicillin anaphylaxis

    Anaphylaxis would show urticaria, bronchospasm or hypotension within minutes.

  • B. Immune-complex serum sickness

    Serum sickness is a type III reaction appearing 1 to 2 weeks after exposure.

  • C. Failure from a penicillin-resistant strain

    Treponema pallidum has never developed penicillin resistance, and failure would not cause an acute febrile surge.

  • D. Cytokine release after spirochaete killing (correct)

    Correct. Cytokine release from dying treponemes explains the early febrile reaction.

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, Cytokine release after spirochaete killing. The Jarisch-Herxheimer reaction follows rapid killing of spirochaetes, releasing lipoproteins that trigger TNF-alpha, interleukin 6 and interleukin 8.

Why is "IgE-mediated penicillin anaphylaxis" not the answer?

Anaphylaxis would show urticaria, bronchospasm or hypotension within minutes.

Why is "Immune-complex serum sickness" not the answer?

Serum sickness is a type III reaction appearing 1 to 2 weeks after exposure.

Why is "Failure from a penicillin-resistant strain" not the answer?

Treponema pallidum has never developed penicillin resistance, and failure would not cause an acute febrile surge.

What concept does this question test?

It tests Bacteriology: Jarisch-Herxheimer reaction in Microbiology. It occurs within hours, settles in 24 hours and is not an allergy, so penicillin should be continued.

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: Jarisch-Herxheimer reaction?

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.