Leprosy: staining: practice question

A Dermatology 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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Dermatology · Leprosy: staining

Sample item

Which stain is preferred for demonstrating M. leprae in tissue sections?

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

The answer and the reasoning

B. Fite-Faraco stain

M. leprae is weakly acid-fast and loses stain with strong acid, so Fite-Faraco, which uses a weaker decolouriser with oil protection, is used for sections. In smears, a modified Ziehl-Neelsen method with 5 percent sulphuric acid is used.

Option by option

  • A. Gram stain

    M. leprae is not well demonstrated by Gram stain.

  • B. Fite-Faraco stain (correct)

    Correct. Fite-Faraco is used for sections.

  • C. Periodic acid-Schiff stain

    PAS stains fungi and glycogen.

  • D. Giemsa stain

    Giemsa is used for Leishman-Donovan bodies and blood films.

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 Dermatology question

What is the answer to this Dermatology question?

The best answer is B, Fite-Faraco stain. M.

Why is "Gram stain" not the answer?

M. leprae is not well demonstrated by Gram stain.

Why is "Periodic acid-Schiff stain" not the answer?

PAS stains fungi and glycogen.

Why is "Giemsa stain" not the answer?

Giemsa is used for Leishman-Donovan bodies and blood films.

What concept does this question test?

It tests Leprosy: staining in Dermatology. leprae is weakly acid-fast and loses stain with strong acid, so Fite-Faraco, which uses a weaker decolouriser with oil protection, is used for sections. In smears, a modified Ziehl-Neelsen method with 5 percent sulphuric acid is used.

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 Leprosy: staining?

Learn each condition by its primary lesion, site and signature sign. Then use the flashcards and the other Dermatology 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.