Bacteriology: neurosyphilis: 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: neurosyphilis

Sample item

A man with untreated syphilis for years develops dementia and ataxia, and has small pupils that constrict to accommodation but not to light. Which test on cerebrospinal fluid supports the diagnosis?

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

The answer and the reasoning

D. Reactive VDRL

A reactive CSF VDRL is highly specific for neurosyphilis, though it may be negative in some cases. Argyll Robertson pupils are accommodation without reaction to light. India ink is for cryptococcus and acid-fast smear for tuberculous meningitis.

Option by option

  • A. India ink preparation

    India ink identifies encapsulated Cryptococcus.

  • B. Latex agglutination for capsular antigen

    Capsular antigen latex agglutination is for bacterial or cryptococcal meningitis.

  • C. Acid-fast smear

    Acid-fast smear looks for mycobacteria, which do not fit this picture.

  • D. Reactive VDRL (correct)

    Correct. CSF VDRL is specific for neurosyphilis.

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, Reactive VDRL. A reactive CSF VDRL is highly specific for neurosyphilis, though it may be negative in some cases.

Why is "India ink preparation" not the answer?

India ink identifies encapsulated Cryptococcus.

Why is "Latex agglutination for capsular antigen" not the answer?

Capsular antigen latex agglutination is for bacterial or cryptococcal meningitis.

Why is "Acid-fast smear" not the answer?

Acid-fast smear looks for mycobacteria, which do not fit this picture.

What concept does this question test?

It tests Bacteriology: neurosyphilis in Microbiology. Argyll Robertson pupils are accommodation without reaction to light. India ink is for cryptococcus and acid-fast smear for tuberculous meningitis.

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: neurosyphilis?

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.