Bacteriology: 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

Sample item

A sewage worker develops fever, jaundice, renal failure and conjunctival suffusion. Which organism is likely, and what is the typical microscopic method for demonstration in blood in the first week?

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

The answer and the reasoning

D. Leptospira interrogans, seen by dark-field microscopy

Weil's disease is severe leptospirosis from contact with water contaminated by rodent urine. Leptospires are thin, tightly coiled spirochaetes too thin to see on Gram stain and are examined by dark-field microscopy. They can be cultured on Fletcher's or EMJH media, and serology uses the microscopic agglutination test.

Option by option

  • A. Borrelia recurrentis, seen on Gram stain

    Borrelia recurrentis can be seen on Giemsa-stained smears but causes louse-borne relapsing fever without renal failure.

  • B. Treponema pallidum, seen by Ziehl-Neelsen stain

    Treponema pallidum is not acid-fast and causes syphilis.

  • C. Brucella melitensis, seen on India ink

    India ink is used for capsules of yeast such as Cryptococcus.

  • D. Leptospira interrogans, seen by dark-field microscopy (correct)

    Correct. Leptospira is demonstrated by dark-field microscopy.

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, Leptospira interrogans, seen by dark-field microscopy. Weil's disease is severe leptospirosis from contact with water contaminated by rodent urine.

Why is "Borrelia recurrentis, seen on Gram stain" not the answer?

Borrelia recurrentis can be seen on Giemsa-stained smears but causes louse-borne relapsing fever without renal failure.

Why is "Treponema pallidum, seen by Ziehl-Neelsen stain" not the answer?

Treponema pallidum is not acid-fast and causes syphilis.

Why is "Brucella melitensis, seen on India ink" not the answer?

India ink is used for capsules of yeast such as Cryptococcus.

What concept does this question test?

It tests Bacteriology in Microbiology. Leptospires are thin, tightly coiled spirochaetes too thin to see on Gram stain and are examined by dark-field microscopy. They can be cultured on Fletcher's or EMJH media, and serology uses the microscopic agglutination test.

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?

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.