Blood culture

What it measures

Grows bacteria or fungi from blood to diagnose bloodstream infection and provide antibiotic sensitivity. It is essential in sepsis, enteric fever and endocarditis.

Specimen and preparation

• Specimen: Whole blood in aerobic and anaerobic culture bottles
• Tube: Other top
• Preparation: Collect 2 sets from separate sites before antibiotics; strict skin antisepsis; adults 8–10 mL per bottle.

Reference range

Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.

Causes of high values

• Bacteremia/sepsis
• Enteric fever (Salmonella Typhi/Paratyphi)
• Infective endocarditis
• Contaminant (skin flora in one set only)

Method

Automated continuous-monitoring culture, Gram stain, identification (MALDI-TOF/biochemical) and AST

Good to know

A positive Gram stain from a blood culture is a critical result to report immediately.

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