A resident plans empirical intravenous antibiotics immediately on arrival for a febrile child with a hot swollen knee, before any aspiration. Why is this sequence wrong?

• A Blood cultures are valid only after 48 hours of antibiotic therapy
• B Aspiration is contraindicated once antibiotics are started
• C Antibiotics must always wait for surgical drainage to be completed
• D Antibiotics given before sampling reduce culture yield substantially without improving outcome ✓

Explanation

Blood cultures and joint or bone aspirates should be obtained before the first dose of antibiotics whenever possible, because even a single dose can render cultures sterile in up to a third of cases while the patient still needs organism identification for de-escalation and duration decisions. Aspiration is not contraindicated afterwards, it simply becomes less often diagnostic. Empirical therapy starts promptly after samples are taken.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.