How soon after being drawn do blood cultures need to be tested?

Blood Culture Transport and Processing Timeline

Blood cultures do NOT need to be tested immediately after being drawn—organisms will survive in inoculated culture vials even if not incubated right away, though transport to the laboratory should occur as soon as possible at room temperature. 1

Standard Blood Culture Transport Guidelines

For Most Common Bacterial Pathogens

The key principle is that while immediate processing is ideal, delayed incubation does not compromise culture yield for standard bacterial pathogens. 1

• Inoculated culture vials should be transported to the laboratory as soon as possible (ASAP) at room temperature 1
• Organisms will usually survive in inoculated culture vials even if not incubated immediately 1
• This applies to the most common bloodstream pathogens including:
  • Staphylococcus species 1
  • Streptococcus species 1
  • Enterococcus species 1
  • Enterobacteriaceae (E. coli, Klebsiella, etc.) 1
  • Pseudomonas and Acinetobacter species 1
  • Anaerobic bacteria 1

Critical Timing for Specific Organisms

Certain fastidious organisms require stricter processing timelines:

• Lysis-centrifugation (Isolator) tubes must be processed within 8 hours of blood inoculation for: 1

  • Bartonella species 1
  • Legionella species 1
  • Filamentous and dimorphic fungi 1

• Yeast (Candida species) cultures should be transported ASAP for early incubation, though organisms will survive if delayed 1

• Mycobacterial blood cultures should be transported ASAP for early incubation 1

Important Clinical Context

Never Refrigerate Blood Cultures

Blood specimens should NEVER be refrigerated prior to incubation—this can kill fastidious organisms and reduce culture yield. 1

Timing Relative to Antibiotic Administration

The more clinically relevant timing issue is obtaining cultures BEFORE antimicrobial therapy, not how quickly they reach the laboratory:

• Blood cultures should be drawn before initiating antimicrobial therapy whenever possible 1, 2
• In critically ill septic patients, do not delay antimicrobials more than 45 minutes to obtain cultures 1, 2
• Administering antibiotics before drawing cultures reduces sensitivity by approximately 50% (from 31.4% to 19.4% positivity in one study when cultures drawn median 70 minutes post-antibiotics) 3

Practical Transport Recommendations

In real-world practice, the following timeline is acceptable:

• Optimal: Transport to laboratory within 1-2 hours of collection 1
• Acceptable: Transport within same work shift (up to 8-12 hours) for standard bacterial cultures 1
• Maximum delay: Most common pathogens remain viable for 24+ hours in culture bottles at room temperature, though this is not recommended practice 1

Common Pitfalls to Avoid

• Do not hold blood cultures at the bedside or nursing station "until convenient"—send immediately even if laboratory processing may be delayed 1
• Do not place blood culture bottles in specimen refrigerators—this is appropriate for other specimens but harmful to blood cultures 1
• Do not assume a delay in transport invalidates the culture—most organisms remain viable and cultures should still be processed 1
• For suspected fastidious organisms (Bartonella, fungi, Legionella), communicate urgency to laboratory to ensure 8-hour processing deadline is met 1