Determining the clinical significance of coagulase-negative staphylococci isolated from blood cultures.
OBJECTIVE
Coagulase-negative staphylococci are both an important cause of nosocomial blood-stream infections and the most common contaminants of blood cultures. Judging the clinical significance of coagulase-negative staphylococci is vital but often difficult and can have a profound impact on an institution's bloodstream infection rates. Our objective was to develop an algorithm to assist in determining the clinical significance of coagulase-negative staphylococci.


METHODS
A single experienced reviewer examined the medical records of 960 consecutive patients with positive blood cultures in a tertiary-care referral teaching hospital. Four hundred five of the cultures contained coagulase-negative staphylococci. A determination of clinical significance was made and the performances of various published algorithms that contained readily available clinical and laboratory data were compared.


RESULTS
Eighty-nine (22%) of the episodes were considered significant, whereas 316 were contaminants. Patients with bacteremia were significantly more likely to be neutropenic and exhibit signs of sepsis syndrome. The algorithm with the best combined sensitivity (62%) and specificity (91%) for determining the clinical significance of coagulase-negative staphylococci was defined as at least two blood cultures positive for coagulase-negative staphylococci within 5 days, or one positive blood culture plus clinical evidence of infection, which includes abnormal white blood cell count and temperature or blood pressure.


CONCLUSIONS
Use of this algorithm could potentially reduce misclassification of nosocomial bloodstream infections and inappropriate use of vancomycin for positive blood cultures likely to represent contamination.
Beekmann
Susan E
SE
Division of Medical Microbiology, Department of Pathology, University of Iowa College of Medicine, Iowa City, Iowa, USA. susan-beekmann@uiowa.edu
Diekema
Daniel J
DJ
Doern
Gary V
GV
D000465:Algorithms; D000704:Analysis of Variance; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D016470:Bacteremia / Q000097:blood / Q000175:diagnosis / Q000188:drug therapy / Q000382:microbiology*; D015373:Bacterial Typing Techniques / Q000379:methods / Q000592:standards; D001800:Blood Specimen Collection / Q000379:methods / Q000592:standards; D003030:Coagulase; D003428:Cross Infection / Q000097:blood / Q000175:diagnosis / Q000188:drug therapy / Q000382:microbiology*; D003663:Decision Trees; D004363:Drug Utilization; D005334:Fever / Q000382:microbiology; D006784:Hospitals, Teaching; D006801:Humans; D017053:Infection Control; D007484:Iowa; D007958:Leukocyte Count; D016013:Likelihood Functions; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D013203:Staphylococcal Infections / Q000097:blood / Q000175:diagnosis / Q000188:drug therapy / Q000382:microbiology*; D013210:Staphylococcus / Q000302:isolation & purification*; D014640:Vancomycin / Q000627:therapeutic use
D000900:Anti-Bacterial Agents; D003030:Coagulase; D014640:Vancomycin