Bacteriology: leptospirosis sampling: 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: leptospirosis sampling

Sample item

A paddy farmer has high fever, conjunctival suffusion, jaundice and renal failure. On which week of illness is culture or PCR of blood most likely to be positive?

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

The answer and the reasoning

D. First week

Leptospires circulate in blood in the first week, the leptospiraemic phase, and are present in urine from the second week. Antibodies by microscopic agglutination test appear after about a week, so serology on a single early sample may be negative.

Option by option

  • A. Third week

    By the third week organisms have left the blood and antibodies dominate.

  • B. Only after recovery

    Waiting for recovery would miss the leptospiraemic window.

  • C. Sixth week

    By the sixth week the infection has resolved or immune phase is over.

  • D. First week (correct)

    Correct. Blood is positive in the first week of illness.

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, First week. Leptospires circulate in blood in the first week, the leptospiraemic phase, and are present in urine from the second week.

Why is "Third week" not the answer?

By the third week organisms have left the blood and antibodies dominate.

Why is "Only after recovery" not the answer?

Waiting for recovery would miss the leptospiraemic window.

Why is "Sixth week" not the answer?

By the sixth week the infection has resolved or immune phase is over.

What concept does this question test?

It tests Bacteriology: leptospirosis sampling in Microbiology. Antibodies by microscopic agglutination test appear after about a week, so serology on a single early sample may be negative.

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: leptospirosis sampling?

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.