Bacteriology: Kingella kingae in children: 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 · Bacteriology: Kingella kingae in children

Sample item

A 15-month-old fully immunised child has a limp and a warm swollen knee with low-grade fever and a mildly raised CRP. Synovial fluid culture on routine agar is sterile at 48 hours, but fluid inoculated into a blood culture bottle grows beta-haemolytic Gram-negative coccobacilli in pairs. Which organism is most likely?

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

The answer and the reasoning

C. Kingella kingae

Kingella kingae is a fastidious member of the oropharyngeal flora that causes osteoarticular infection in children under 4 years. Inoculating joint fluid into blood culture bottles greatly improves recovery, and the infection is often milder than that caused by Staphylococcus aureus.

Option by option

  • A. Streptococcus pyogenes

    Streptococcus pyogenes is a Gram-positive coccus in chains and also grows on routine media.

  • B. Haemophilus influenzae type b

    Haemophilus influenzae type b is much less likely in a fully immunised child and needs X and V factors.

  • C. Kingella kingae (correct)

    Correct. A fastidious Gram-negative coccobacillus recovered only in blood culture bottles points to Kingella.

  • D. Staphylococcus aureus

    Staphylococcus aureus is a Gram-positive coccus that grows readily on routine agar.

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 C, Kingella kingae. Kingella kingae is a fastidious member of the oropharyngeal flora that causes osteoarticular infection in children under 4 years.

Why is "Streptococcus pyogenes" not the answer?

Streptococcus pyogenes is a Gram-positive coccus in chains and also grows on routine media.

Why is "Haemophilus influenzae type b" not the answer?

Haemophilus influenzae type b is much less likely in a fully immunised child and needs X and V factors.

Why is "Staphylococcus aureus" not the answer?

Staphylococcus aureus is a Gram-positive coccus that grows readily on routine agar.

What concept does this question test?

It tests Bacteriology: Kingella kingae in children in Microbiology. Inoculating joint fluid into blood culture bottles greatly improves recovery, and the infection is often milder than that caused by Staphylococcus aureus.

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 Bacteriology: Kingella kingae in children?

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.