Virus detection: haemadsorption: 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 · Virus detection: haemadsorption

Sample item

A parainfluenza virus is inoculated into monkey kidney cell monolayers, but no cytopathic effect develops after a week. Which simple test can show that the virus has replicated?

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

The answer and the reasoning

D. Haemadsorption with guinea pig red cells

Parainfluenza and influenza viruses insert haemagglutinin into the membrane of infected cells. When guinea pig red blood cells are added, they stick to these cells, which is haemadsorption, even in the absence of cytopathic effect. A related method is haemagglutination of the culture fluid.

Option by option

  • A. Giemsa staining for Negri bodies

    Negri bodies are cytoplasmic inclusions of rabies infection and are not relevant here.

  • B. Culture on Lowenstein-Jensen medium

    Lowenstein-Jensen medium grows mycobacteria and not viruses.

  • C. Plaque reduction assay

    Plaque assays need visible cell destruction, which is absent here.

  • D. Haemadsorption with guinea pig red cells (correct)

    Correct. Red cells adhering to infected cells reveal viral haemagglutinin.

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, Haemadsorption with guinea pig red cells. Parainfluenza and influenza viruses insert haemagglutinin into the membrane of infected cells.

Why is "Giemsa staining for Negri bodies" not the answer?

Negri bodies are cytoplasmic inclusions of rabies infection and are not relevant here.

Why is "Culture on Lowenstein-Jensen medium" not the answer?

Lowenstein-Jensen medium grows mycobacteria and not viruses.

Why is "Plaque reduction assay" not the answer?

Plaque assays need visible cell destruction, which is absent here.

What concept does this question test?

It tests Virus detection: haemadsorption in Microbiology. When guinea pig red blood cells are added, they stick to these cells, which is haemadsorption, even in the absence of cytopathic effect. A related method is haemagglutination of the culture fluid.

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 Virus detection: haemadsorption?

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.