Determination of clinical significance of coagulase-negative staphylococci in blood cultures

The aim of this study was to investigate the criteria used to distinguish coagulase-negative staphylococci (CoNS) bacteremia from contamination. We evaluated 162 adult patients with CoNS-positive blood cultures (BCs). Of the 162 patients, 35 (21.6%) had at least 2 positive BCs and 127 (78.4%) had a single positive BC. According to the Laboratory-Confirmed Bloodstream Infection (LCBI) criteria, 24 (14.8%) patients with the same species of CoNS had true bacteremia, and 138 (85.2%) patients had contaminants. Despite the detection of the same CoNS species, 9 of the 24 patients had different CoNS genotypes. Using clinical assessments, only 20 patients were diagnosed with true bacteremia, 8 of them had a single positive BC. We concluded that only using the LCBI criteria or clinical evaluations of a patient were not sufficient to distinguish CoNS bacteremia from contamination. Molecular identification should also be performed as a diagnostic laboratory parameter for CoNS bacteremia.