Brucella: blood culture technique: 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 · Brucella: blood culture technique

Sample item

A laboratory in Punjab suspects brucellosis in a dairy farmer and wants to culture his blood while keeping laboratory staff safe and avoiding repeated opening of the bottle. Which technique is best?

ACastaneda biphasic bottle with broth and agar slant, incubated up to 4 weeksBThioglycollate broth incubated anaerobicallyCBlood agar plate incubated aerobically for 24 hoursDLowenstein-Jensen slope incubated at 37 degrees C

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

The answer and the reasoning

A. Castaneda biphasic bottle with broth and agar slant, incubated up to 4 weeks

The Castaneda method uses a single bottle with broth and an agar slant. The broth is tilted over the slant at intervals, so subculture is done without opening the bottle, lowering contamination and aerosol risk. Brucella grows slowly, so incubation is prolonged, up to 4 weeks, with capnophilic conditions for some species.

Option by option

A. Castaneda biphasic bottle with broth and agar slant, incubated up to 4 weeks (correct)
Correct. A biphasic bottle allows serial subculture without opening and supports slow growth.
B. Thioglycollate broth incubated anaerobically
Brucella is a strict aerobe, so anaerobic thioglycollate culture is not appropriate.
C. Blood agar plate incubated aerobically for 24 hours
A single aerobic blood agar plate for 24 hours is too short for slow-growing Brucella and requires opening the culture.
D. Lowenstein-Jensen slope incubated at 37 degrees C
Lowenstein-Jensen medium is for mycobacteria and not the standard for Brucella blood culture.

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 A, Castaneda biphasic bottle with broth and agar slant, incubated up to 4 weeks. The Castaneda method uses a single bottle with broth and an agar slant.

Why is "Thioglycollate broth incubated anaerobically" not the answer?

Brucella is a strict aerobe, so anaerobic thioglycollate culture is not appropriate.

Why is "Blood agar plate incubated aerobically for 24 hours" not the answer?

A single aerobic blood agar plate for 24 hours is too short for slow-growing Brucella and requires opening the culture.

Why is "Lowenstein-Jensen slope incubated at 37 degrees C" not the answer?

Lowenstein-Jensen medium is for mycobacteria and not the standard for Brucella blood culture.

What concept does this question test?

It tests Brucella: blood culture technique in Microbiology. The broth is tilted over the slant at intervals, so subculture is done without opening the bottle, lowering contamination and aerosol risk. Brucella grows slowly, so incubation is prolonged, up to 4 weeks, with capnophilic conditions for some species.

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 Brucella: blood culture technique?

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.