Diagnosis & Contaminants

Diagnosis & Contaminants

Blood Cultures

Every effort should be made to obtain 2 sets of blood cultures from a peripheral site AND 2 sets from the central line, prior to antibiotic initiation

If ideal conditions unable to be met, consider at minimum:

  • At least one set from peripheral site (in addition to 2 sets from central line)
  • If peripheral not possible obtain 2 or more sets through different catheter lumens
  • All catheter lumens should have at least an aerobic culture drawn
  • Port-a-cath must be accessed for culture prior to antibiotics

Note: Results of a single blood culture set are more difficult to interpret than results of multiple sets; additionally, catheters may be colonized with skin contaminants and should not be the sole source for blood cultures

Catheter-Related Cultures

  • Utility not well defined; should NOT routinely be obtained
  • If exudate is present, swab drainage and send for gram stain and culture


Paired blood cultures from both peripheral and line growing the same organism supports central line associated bloodstream infection (CLABSI) diagnosis

Often only line cultures are available; important to have multiple cultures from the line to help clarify contaminant vs true infection


Central lines are a foreign body; it is important to obtain multiple cultures from all lumens and peripheral cultures to determine true line infection vs contamination

Many organisms typically considered contaminants for non-line associated bacteremia may actually be responsible for a CLABSI

  • Coagulase negative Staphylococci (except S. lugdunensis)

  • Viridans group Streptococci

  • Micrococcus species

  • Aerococcus species

  • Corynebacterium species

  • Cutibacterium species

  • Bacillus (non-anthracis) species