Taking blood cultures before antibiotics
PLAB 2 & PRES 3 · practical skills / emergency medicine · medium · 8 minutes
Candidate brief
You are an FY2 doctor in the emergency department. Mrs Funke Adeyemi, 69, has presented with fever, rigors and right flank pain, and the consultant suspects pyelonephritis with sepsis. Observations: temperature 39.2 °C, heart rate 118, blood pressure 104/62 mmHg, respiratory rate 22, oxygen saturations 96% on air. The consultant has asked you to take blood cultures BEFORE her first dose of intravenous antibiotics, and then ensure the antibiotics are given promptly. Please take the blood cultures. Verbalise each step as you perform it.
What examiners look for
Order matters, but so does the clock. Cultures before antibiotics is one of the few sequencing rules in sepsis that genuinely changes diagnostic yield — and it is paired with an equally firm rule that antibiotics should be given within the hour. The skill is doing both: one clean, efficient draw, then treatment. Contamination is the silent failure of this station. Skin flora in a culture bottle produces false positives, unnecessary antibiotics, extra days in hospital and wrong conclusions about lines and valves. The disciplines that prevent it are unglamorous: fresh peripheral site, dried antiseptic on skin AND bottle tops, and never touching a disinfected surface again. Volume is yield. Under-filled bottles are the commonest technical reason for a false-negative culture in a genuinely bacteraemic patient. In adults, aim for around 8–10 ml per bottle; two bottles (aerobic and anaerobic) also widen the range of organisms recovered. Know which bottle first. With a winged (butterfly) collection set, the aerobic bottle is filled first because of air in the tubing; when transferring from a syringe, the anaerobic bottle is filled first. Examiners who know blood cultures ask — and it signals real ward experience. Allergy history belongs to this station even though someone else prescribes. The penicillin rash was in this patient's history waiting to be asked for; a practical-skills station that surfaces and hands over a prescribing hazard scores exactly like the real job. A retired midwife is the examiner's gift: she represents the informed patient who notices technique. Practical stations increasingly include patients who watch, and narrating clean technique aloud ("I'm letting that dry so it's properly sterile") is both good practice and good marks.
Guideline references
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