Bacteriology: Campylobacter jejuni: 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: Campylobacter jejuni

Sample item

A 28-year-old man develops ascending symmetrical weakness with areflexia two weeks after an episode of bloody diarrhoea. Stool culture, if it were still positive, would grow curved Gram-negative rods on selective medium incubated at 42 degrees C in a microaerophilic atmosphere. Which organism and mechanism explain the neurological illness?

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

The answer and the reasoning

A. Campylobacter jejuni, with lipooligosaccharide mimicking peripheral nerve gangliosides

Campylobacter jejuni is the most common antecedent infection of Guillain-Barre syndrome. Antibodies against bacterial lipooligosaccharide cross-react with gangliosides such as GM1 on peripheral nerves, an example of molecular mimicry. The organism grows at 42 degrees C on Skirrow medium in reduced oxygen.

Option by option

  • A. Campylobacter jejuni, with lipooligosaccharide mimicking peripheral nerve gangliosides (correct)

    Molecular mimicry between bacterial lipooligosaccharide and gangliosides explains post-Campylobacter Guillain-Barre syndrome.

  • B. Shigella dysenteriae, with Shiga toxin damaging motor neurons directly

    Shiga toxin causes haemolytic uraemic syndrome, not an immune-mediated neuropathy.

  • C. Clostridioides difficile, with toxin A crossing the blood-nerve barrier

    C. difficile toxins act on the colon and do not cause an ascending demyelinating neuropathy.

  • D. Salmonella Typhi, with Vi antigen depositing in nerve sheaths

    The Vi antigen is a capsule of Salmonella Typhi and is not linked to Guillain-Barre syndrome.

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 A, Campylobacter jejuni, with lipooligosaccharide mimicking peripheral nerve gangliosides. Campylobacter jejuni is the most common antecedent infection of Guillain-Barre syndrome.

Why is "Shigella dysenteriae, with Shiga toxin damaging motor neurons directly" not the answer?

Shiga toxin causes haemolytic uraemic syndrome, not an immune-mediated neuropathy.

Why is "Clostridioides difficile, with toxin A crossing the blood-nerve barri…" not the answer?

C. difficile toxins act on the colon and do not cause an ascending demyelinating neuropathy.

Why is "Salmonella Typhi, with Vi antigen depositing in nerve sheaths" not the answer?

The Vi antigen is a capsule of Salmonella Typhi and is not linked to Guillain-Barre syndrome.

What concept does this question test?

It tests Bacteriology: Campylobacter jejuni in Microbiology. Antibodies against bacterial lipooligosaccharide cross-react with gangliosides such as GM1 on peripheral nerves, an example of molecular mimicry. The organism grows at 42 degrees C on Skirrow medium in reduced oxygen.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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: Campylobacter jejuni?

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.