Bacteraemia and occult bloodstream infection — formative SAQs

SAQ 1 (10 marks, 15 minutes)

Stem. A 14-month-old, fully immunised boy is brought to the emergency department with two days of fever to 39.5 °C. He is alert, smiling, drinks from his cup, has a clear chest, no rash, normal perfusion and no identifiable focus. His immunisations are up to date, including pneumococcal conjugate vaccine. Outline your assessment, the investigation you would and would not perform, and the safety-net you would give. ^[9]

Model answer — SAQ 1

The priority is to recognise that this is a well-appearing vaccinated child in the post-conjugate-vaccine era, where the prevalence of occult bacteraemia has fallen to well below one per cent. The clinical question is no longer "is the blood culture going to be positive?" but "is this child at risk of invasive bacterial infection, and can I safely defer empiric antibiotics?" ^{[1] [9]}

I would state the appearance explicitly — alert, interactive, normal colour, tone and perfusion, drinking well — because appearance is the single most powerful bedside discriminator. I would measure age-adjusted observations and perform a focused focus search: ears, throat, chest, abdomen, skin, joints and central nervous system. A urine test (clean catch or catheter) is reasonable in this age group for an unexplained fever, because urinary tract infection is the commonest serious bacterial infection in febrile infants. ^{[1] [3]}

I would not routinely perform a blood culture or give empirical ceftriaxone, because routine expectant observation was justified in the pre-vaccine era when occult pneumococcal bacteraemia carried a real risk of meningitis, and that prevalence has collapsed with conjugate vaccines. I would reserve blood culture and inflammatory markers for higher-risk features: a high or prolonged fever, an abnormal appearance, an identified focus, a vulnerable host, or incomplete immunisation. ^{[1] [9]}

My safety-net would be specific, not "return if worried": the warning changes to watch for (reduced feeding, lethargy, reduced wet nappies, altered breathing, a rash, or the child not being their usual self), the urgency (immediately if any appear), and the exact access route. I would name a clinician who owns any pending test result, confirm understanding with teach-back, and connect the family to primary care follow-up. A brief improvement after antipyretics does not by itself make the child safe; what matters is sustained return to usual behaviour. ^{[1] [3]}

Marking grid — SAQ 1

Common pitfalls — SAQ 1

• Applying the 1990s expectant-observation practice (routine culture plus empirical ceftriaxone) to a well-appearing vaccinated toddler.
• Using "return if worried" as the entire safety-net.
• Failing to name an owner for a pending urine or other test.
• Missing a urinary tract infection because no urine was tested in a febrile infant.
• Anchoring on a reassuring antipyretic response without assessing sustained recovery. ^{[1] [3] [9]}