Virology: congenital cytomegalovirus: 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 · Virology: congenital cytomegalovirus

Sample item

A newborn has microcephaly, periventricular calcifications, petechiae, hepatosplenomegaly and sensorineural hearing loss. Which test best shows that the infection was congenital?

ATuberculin skin test of the newbornBCMV IgG in the mother's serum after deliveryCCMV IgG in the newborn's serumDCMV PCR or culture of urine or saliva in the first 3 weeks of life

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

The answer and the reasoning

D. CMV PCR or culture of urine or saliva in the first 3 weeks of life

Congenital cytomegalovirus infection is the commonest congenital viral infection and a leading cause of non-genetic sensorineural deafness. Detecting virus in urine or saliva within the first 2 to 3 weeks proves infection acquired before birth, because later positive tests may reflect postnatal infection. IgG is of maternal origin.

Option by option

A. Tuberculin skin test of the newborn
Tuberculin testing is not relevant to this viral infection.
B. CMV IgG in the mother's serum after delivery
Maternal IgG shows only past exposure and does not prove fetal infection.
C. CMV IgG in the newborn's serum
Infant IgG largely reflects maternal antibody transferred across the placenta.
D. CMV PCR or culture of urine or saliva in the first 3 weeks of life (correct)
Correct. Early virus detection in urine or saliva identifies congenital infection.

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 D, CMV PCR or culture of urine or saliva in the first 3 weeks of life. Congenital cytomegalovirus infection is the commonest congenital viral infection and a leading cause of non-genetic sensorineural deafness.

Why is "Tuberculin skin test of the newborn" not the answer?

Tuberculin testing is not relevant to this viral infection.

Why is "CMV IgG in the mother's serum after delivery" not the answer?

Maternal IgG shows only past exposure and does not prove fetal infection.

Why is "CMV IgG in the newborn's serum" not the answer?

Infant IgG largely reflects maternal antibody transferred across the placenta.

What concept does this question test?

It tests Virology: congenital cytomegalovirus in Microbiology. Detecting virus in urine or saliva within the first 2 to 3 weeks proves infection acquired before birth, because later positive tests may reflect postnatal infection. IgG is of maternal origin.

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 Virology: congenital cytomegalovirus?

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.