Blood culture contamination

• Almost never true bacteremia (almost always contaminant)
  • Corynebacterium, except Corynebacterium jeikeium
  • Bacillus, except Bacillus anthracis
  • Cutibacterium acnes
• Sometimes true bacteremia
  • Micrococcus
  • Clostridium perfringens
  • Coagulase-negative staphylococci
  • Viridans group streptococci
  • Lactobacillus
  • Nutritionally variant streptococci (Abiotrophia and Granulicatella)
• Often true bacteremia
  • Enterococcus
  • Aerococcus
• Always true bacteremia (or at least, always treated as such)
  • Staphylococcus aureus
  • Streptococcus pneumoniae
  • Escherichia coli and other Enterobacterales
  • Pseudomonas aeruginosa
  • Candida albicans
• Coagulase-negative staphylococci are rarely significant (12%), but because they are so common (70-80% of all positive cultures), they are the most common cause of bacteremia

Further Reading

• Laboratory approaches to determining blood culture contamination rates: an ASM Laboratory Practices Subcommittee report. J Clin Microbiol. 2023;62:e01028-23. doi: 10.1128/jcm.01028-23