General microbiology and sterilisation: 16S rRNA sequencing: 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 · General microbiology and sterilisation: 16S rRNA sequencing

Sample item

A patient with a prosthetic valve has culture-negative endocarditis after antibiotics were given. A resected vegetation is amplified with broad-range primers, and the product is sequenced to identify the organism. Which gene is targeted?

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

The answer and the reasoning

B. 16S ribosomal RNA gene

The 16S rRNA gene contains conserved regions that allow universal primers and variable regions that identify genus and species, so it is used for identifying unculturable or fastidious bacteria directly from tissue. The mecA gene only indicates methicillin resistance, and it does not identify the organism. Results must be interpreted with clinical findings and contamination controls.

Option by option

  • A. mecA gene

    mecA detects methicillin resistance in staphylococci and does not identify an unknown organism.

  • B. 16S ribosomal RNA gene (correct)

    Correct. Conserved 16S rRNA sequences permit broad-range amplification, and variable regions identify the organism.

  • C. Gene for a 70 kDa heat shock protein of the host

    A host heat shock protein gene would amplify human DNA rather than identify bacteria.

  • D. Gene encoding beta-lactamase

    Beta-lactamase genes show resistance potential in specific species and are not universal.

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 B, 16S ribosomal RNA gene. The 16S rRNA gene contains conserved regions that allow universal primers and variable regions that identify genus and species, so it is used for identifying unculturable or fastidious bacteria directly from tissue.

Why is "mecA gene" not the answer?

mecA detects methicillin resistance in staphylococci and does not identify an unknown organism.

Why is "Gene for a 70 kDa heat shock protein of the host" not the answer?

A host heat shock protein gene would amplify human DNA rather than identify bacteria.

Why is "Gene encoding beta-lactamase" not the answer?

Beta-lactamase genes show resistance potential in specific species and are not universal.

What concept does this question test?

It tests General microbiology and sterilisation: 16S rRNA sequencing in Microbiology. The mecA gene only indicates methicillin resistance, and it does not identify the organism. Results must be interpreted with clinical findings and contamination controls.

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 General microbiology and sterilisation: 16S rRNA sequencing?

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.