General microbiology and sterilisation: Kauffmann-White scheme: 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: Kauffmann-White scheme

Sample item

A Salmonella isolate agglutinates with O group D (O9) antiserum, with H antiserum d, and with Vi antiserum. According to the Kauffmann-White scheme, which serovar is it?

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

The answer and the reasoning

B. Salmonella Typhi

The Kauffmann-White scheme classifies Salmonella by O, H and Vi antigens. S. Typhi carries O9 and O12 (group D), the flagellar H antigen d and the Vi capsular antigen. Other serovars of group D, such as Enteritidis, carry different H antigens and no Vi.

Option by option

  • A. Salmonella Paratyphi B

    S. Paratyphi B belongs to O group B (O4) with H:b and has no Vi antigen.

  • B. Salmonella Typhi (correct)

    Correct. O9 with H:d and the Vi antigen defines S. Typhi.

  • C. Salmonella Paratyphi A

    S. Paratyphi A belongs to O group A (O2) with H:a and has no Vi antigen.

  • D. Salmonella Enteritidis

    S. Enteritidis shares O9 but has H antigens g,m and no Vi antigen.

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, Salmonella Typhi. The Kauffmann-White scheme classifies Salmonella by O, H and Vi antigens.

Why is "Salmonella Paratyphi B" not the answer?

S. Paratyphi B belongs to O group B (O4) with H:b and has no Vi antigen.

Why is "Salmonella Paratyphi A" not the answer?

S. Paratyphi A belongs to O group A (O2) with H:a and has no Vi antigen.

Why is "Salmonella Enteritidis" not the answer?

S. Enteritidis shares O9 but has H antigens g,m and no Vi antigen.

What concept does this question test?

It tests General microbiology and sterilisation: Kauffmann-White scheme in Microbiology. S. Typhi carries O9 and O12 (group D), the flagellar H antigen d and the Vi capsular antigen. Other serovars of group D, such as Enteritidis, carry different H antigens and no Vi.

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 General microbiology and sterilisation: Kauffmann-White scheme?

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.