Which of the following statements is not true about blood cultures for recovering bacteria?

• A. No more than three cultures should be drawn in 1 day.
• B. Cultures should be drawn before the expected fever spike.
• C. Cultures should be incubated aerobically and anaerobically.
• D. Collect 5 mL of blood for optimal recovery of pathogen.

Answer: (D)

The key idea is that blood culture yield depends on collecting enough blood, at the right time, and using proper processing to detect bacteria in the bloodstream. For adults, maximizing recovery requires a larger volume than 5 mL per culture bottle—typically about 8–10 mL per bottle, with two bottles per set (one aerobic and one anaerobic), and usually two to three sets drawn from separate sites, totaling roughly 20–30 mL per set. Collecting only 5 mL would significantly lower the chance of detecting the pathogen. Cultures are drawn before starting antibiotics to avoid suppressing bacterial growth and to improve yield, and timing around fever onset is used to capture bacteremia when it’s most detectable. Incubating both aerobically and anaerobically covers organisms with different oxygen requirements, preventing misses of anaerobic pathogens. Therefore, the statement about collecting 5 mL of blood for optimal recovery is not true, since it underestimates the volume needed for reliable detection.