Blood culture contamination
From IDWiki
| Frequency of True Bacteremia | Organism | Gram Stain |
|---|---|---|
| Almost never true bacteremia (almost always contaminant) | Corynebacterium, except Corynebacterium jeikeium | Gram-positive bacillus |
| Bacillus, except Bacillus anthracis | Gram-positive bacillus | |
| Cutibacterium acnes | Gram-positive bacillus | |
| Sometimes true bacteremia | Micrococcus | Gram-positive cocci in groups |
| Clostridium perfringens | Anaerobic Gram-positive bacillus | |
| Coagulase-negative staphylococci, except Staphylococcus lugdenensis | Gram-positive cocci in groups | |
| Viridans group streptococci | Gram-positive cocci in pairs and chains | |
| Lactobacillus | Gram-positive bacillus | |
| Nutritionally variant streptococci (Abiotrophia and Granulicatella) | Gram-positive cocci in pairs and chains | |
| Usually true bacteremia | Enterococcus | Gram-positive cocci in pairs and chains |
| Aerococcus | Gram-positive cocci in pairs and chains | |
| Always true bacteremia (or at least, always treated as such) | Staphylococcus aureus | Gram-positive cocci in groups |
| Staphylococcus lugdenensis | Gram-positive cocci in groups | |
| Streptococcus pneumoniae | Gram-positive cocci in pairs and chains | |
| Escherichia coli and other Enterobacterales | Gram-negative bacilli | |
| Pseudomonas aeruginosa | Gram-negative bacilli | |
| Candida | Yeast |
- 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
