Determining the significance of coagulase-negative staphylococci isolated from blood cultures at a community hospital: a role for species and strain identification

Infect Control Hosp Epidemiol. 2000 Mar;21(3):213-7. doi: 10.1086/501747.

Abstract

Objectives: To determine the degree to which species identification or strain relatedness assessment of successive blood culture isolates of coagulase-negative staphylococci (CNS) may improve the clinical diagnosis of bloodstream infection (BSI).

Setting: 400-bed community hospital.

Design: Prospective laboratory survey during which all CNS blood culture isolates obtained between mid-August 1996 and mid-February 1997 (study period) were saved and later identified to the species level; selected isolates were genotyped using pulsed-field gel electrophoresis at the Centers for Disease Control and Prevention (CDC). Retrospective review of medical records of 37 patients with multiple cultures positive for CNS.

Results: During the study period, 171 patients had blood cultures positive for CNS; 130 had single positive cultures and 41 had > or =2 positive cultures. Of these 41, 23 (62%) were from patients with signs and symptoms of BSI according to CDC surveillance definitions. Species identification and strain clonality of CNS isolates from patients with > or =2 positives revealed 3 (13%) of the 23 patients did not have a consistent CNS species, and another 3 (13%) did not have a consistent genotype in the > or =2 positive cultures, suggesting that CNS from these patients probably were contaminants. Thus, species identification and strain clonality assessment reduced by 27% the number of patients with BSI diagnosed based on the presence of symptoms and > or =2 positive blood cultures.

Conclusions: Routine species identification and selected strain genotyping of CNS may reduce the misinterpretation of probable contaminants among patients with > or =2 positive blood cultures.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Bacteremia / diagnosis
  • Bacteremia / microbiology
  • Bacterial Typing Techniques
  • Child
  • Child, Preschool
  • Coagulase / analysis*
  • Female
  • Hospital Bed Capacity, 300 to 499
  • Hospitals, Community
  • Humans
  • Infant
  • Infant, Newborn
  • Male
  • Medical Audit
  • Middle Aged
  • Species Specificity
  • Staphylococcus / enzymology*
  • Staphylococcus / genetics
  • Staphylococcus / isolation & purification

Substances

  • Coagulase