Blood culture isolates were categorized into two groups including a true pathogen and a contaminant by clinical criteria combined with laboratory data. A blood culture was classified as contaminated if common skin flora such as Coagulase negative staphylococci, Corynebacterium spp., Micrococcus spp., or Bacillus spp. were isolated from one of the blood culture samples without isolation of the same organism from another potential infection site (for example, intravenous catheter), or a common skin flora was isolated in a patient with incompatible clinical features and improved without specific treatment for that organism.