Bacteriology: Borrelia recurrentis: 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: Borrelia recurrentis

Sample item

A homeless man in a crowded shelter has abrupt high fever, headache and myalgia for 4 days that resolves by crisis and recurs after a week. A smear taken during fever shows loosely coiled spirochaetes among red cells. Which mechanism best explains the relapses?

AAntigenic variation of surface variable major proteinsBIntracellular persistence as cell-wall-deficient L-formsCReactivation of latent organisms in sensory gangliaDDormant hypnozoites in the liver

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

The answer and the reasoning

A. Antigenic variation of surface variable major proteins

Louse-borne relapsing fever is caused by Borrelia recurrentis. The spirochaete switches its variable major surface proteins by gene rearrangement, so antibody raised against one antigenic type does not clear the next, and each variant produces a new febrile relapse. Penicillin or tetracycline can trigger a Jarisch-Herxheimer reaction.

Option by option

A. Antigenic variation of surface variable major proteins (correct)
Correct. Each antigenic variant escapes the previous antibody response and drives a new relapse.
B. Intracellular persistence as cell-wall-deficient L-forms
L-form persistence is not the cause of relapse in relapsing fever.
C. Reactivation of latent organisms in sensory ganglia
Latent reactivation in ganglia describes herpes simplex and varicella zoster viruses.
D. Dormant hypnozoites in the liver
Hypnozoites cause relapses in vivax and ovale malaria, not in spirochaetal infection.

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 A, Antigenic variation of surface variable major proteins. Louse-borne relapsing fever is caused by Borrelia recurrentis.

Why is "Intracellular persistence as cell-wall-deficient L-forms" not the answer?

L-form persistence is not the cause of relapse in relapsing fever.

Why is "Reactivation of latent organisms in sensory ganglia" not the answer?

Latent reactivation in ganglia describes herpes simplex and varicella zoster viruses.

Why is "Dormant hypnozoites in the liver" not the answer?

Hypnozoites cause relapses in vivax and ovale malaria, not in spirochaetal infection.

What concept does this question test?

It tests Bacteriology: Borrelia recurrentis in Microbiology. The spirochaete switches its variable major surface proteins by gene rearrangement, so antibody raised against one antigenic type does not clear the next, and each variant produces a new febrile relapse. Penicillin or tetracycline can trigger a Jarisch-Herxheimer reaction.

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: Borrelia recurrentis?

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.