Clinical microbiology and hospital infection control: blood culture yield: 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 · Clinical microbiology and hospital infection control: blood culture yield

Sample item

Which factor most strongly determines the yield of blood cultures in adults with bacteraemia?

ARefrigerating bottles before incubationBDrawing only from an existing central lineCThe volume of blood inoculated into each bottleDTiming the draw exactly at the fever peak

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

The answer and the reasoning

C. The volume of blood inoculated into each bottle

Bacteraemia in adults often involves very few organisms per millilitre, so the volume of blood cultured is the main determinant of sensitivity. Sets should be drawn before antibiotics, from separate sites.

Option by option

A. Refrigerating bottles before incubation
Refrigeration kills fastidious organisms and delays growth.
B. Drawing only from an existing central line
Drawing only through an existing line raises contamination and misleads interpretation.
C. The volume of blood inoculated into each bottle (correct)
Correct. Sensitivity rises with the volume of blood cultured.
D. Timing the draw exactly at the fever peak
Bacteraemia is often continuous, and timing to the fever peak adds little.

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.

Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is C, The volume of blood inoculated into each bottle. Bacteraemia in adults often involves very few organisms per millilitre, so the volume of blood cultured is the main determinant of sensitivity.

Why is "Refrigerating bottles before incubation" not the answer?

Refrigeration kills fastidious organisms and delays growth.

Why is "Drawing only from an existing central line" not the answer?

Drawing only through an existing line raises contamination and misleads interpretation.

Why is "Timing the draw exactly at the fever peak" not the answer?

Bacteraemia is often continuous, and timing to the fever peak adds little.

What concept does this question test?

It tests Clinical microbiology and hospital infection control: blood culture yield in Microbiology. Sets should be drawn before antibiotics, from separate sites.

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 Clinical microbiology and hospital infection control: blood culture yield?

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.