Skin Contamination and Blood Cultures

There are really only four bugs that are commonly contaminants when blood cultures are positive:

1. Coag negative staph (gram positive cocci)
2. Corynebacterium (gram positive rods)
3. Propionibacterium acnes (anaerobic gram positive rods)
4. Bacillus species (anaerobic gram positive rods)

While these are commonly contaminants, be careful to rule out true infection in the following settings:

• When multiple blood cultures from different sets are positive
• When the patient has prosthetic devices

The following bugs are generally NOT skin contaminants are warrant further workup:

• Strep species
• Staph aureus
• Enterococcus
• Candida
• Pseudomonas and other Gram negative rods

(Chanu Rhee MD, 5/19/11)