Skip to main content

Determining the Clinical Significance of Coagulase-Negative Staphylococci Isolated From Blood Cultures

  • Susan E. Beekmann (a1), Daniel J. Diekema (a2) and Gary V. Doern (a1)
AbstractBackground and Objective:

Coagulase-negative staphylococci are both an important cause of nosocomial bloodstream 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.


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.


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.


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 (Infect Control Hosp Epidemiol 2005;26:559-566).

Corresponding author
University of Iowa, 265 MRC, Iowa City, IA
Hide All
1.Weinstein, MP, Towns, ML, Quartey, SM, et al.The clinical significance of positive blood cultures in the 1990s: a prospective comprehensive evaluation of the microbiology, epidemiology, and outcome of bacteremia and fungemia in adults. Clin Infect Dis 1997;24:584602.
2.Edmond, MB, Wallace, SE, McClish, DK, Pfaller, MA, Jones, RN, Wenzel, RP. Nosocomial bloodstream infections in United States hospitals: a three-year analysis. Clin Infect Dis 1999;29:239244.
3.Diekema, DJ, Beekmann, SE, Chapin, KC, Morel, KA, Munson, EL, Doern, GV. Epidemiology and outcome of nosocomial and community-onset bloodstream infection. J Clin Microbiol 2003;41:36553660.
4.Thylefors, JD, Harbarth, S, Pittet, D. Increasing bacteremia due to coagulase-negative staphylococci: fiction or reality? Infect Control Hosp Epidemiol 1998;19:581589.
5.Bates, DW, Goldman, L, Lee, TH. Contaminant blood cultures and resource utilization: the true consequences of false-positive results. JAMA 1991;265:365369.
6.Souvenir, D, Anderson, DE Jr, Palpant, S, et al.Blood cultures positive for coagulase-negative staphylococci: antisepsis, pseudobacteremia, and therapy of patients. J Clin Microbiol 1998;36:19231926.
7.Weinstein, MP. Blood culture contamination: persisting problems and partial progress. J Clin Microbiol 2003;41:22752278.
8.Richter, SS, Beekmann, SE, Croco, JL, et al.Minimizing the workup of blood culture contaminants: implementation and evaluation of a laboratory-based algorithm. J Clin Microbiol 2002;40:24372444.
9.Sharma, M, Riederer, K, Johnson, LB, Khatib, R. Molecular analysis of coagulase-negative Staphylococcus isolates from blood cultures: prevalence of genotypic variation and polyclonal bacteremia. Clin Infect Dis 2001;33:13171323.
10.Kim, SD, McDonald, LC, Jarvis, WR, et al.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;21:213217.
11.Seo, SK, Venkataraman, L, DeGirolami, PC, Samore, MH. Molecular typing of coagulase-negative staphylococci from blood cultures does not correlate with clinical criteria for true bacteremia. Am J Med 2000;109:697704.
12.Lyytikainen, O, Valtonen, V, Anttila, VJ, Ruutu, P. Evaluation of clinical and laboratory findings in leukaemic patients with blood cultures positive for Staphylococcus epidermidis. J Hosp Infect 1998;38:2735.
13.Herwaldt, LA, Geiss, M, Kao, C, Pfaller, MA. The positive predictive value of isolating coagulase-negative staphylococci from blood cultures. Clin Infect Dis 1996;22:1420.
14.Centers for Disease Control and Prevention. Guidelines for the prevention of intravascular catheter-related infections. MMWR 2002;51 (RR-10): 136.
15.Khatib, R, Riederer, K, Clark, JA, Khatib, S, Briski, LE, Wilson, FM. Coagulase-negative staphylococci in multiple blood cultures: strain relatedness and determinants of same-strain bacteremia. J Clin Microbiol 1994;33:816820.
16.Kirchhoff, LV, Sheagren, JN. Epidemiology and clinical significance of blood cultures positive for coagulase-negative staphylococci. Infect Control 1985;6:479486.
17.Fidalgo, S, Vazquez, F, Mendoza, MC, Perez, F, Mendez, FJ. Bacteremia due to Staphylococcus epidermidis: microbiologic, epidemiologic, clinical, and prognostic features. Rev Infect Dis 1990;12:520528.
18.Martin, MA, Pfaller, MA, Wenzel, RP. Coagulase-negative staphylococcal bacteremia: mortality and hospital stay. Ann Intern Med 1989;110:916.
19.MacGregor, RR, Beaty, HN. Evaluation of positive blood cultures: guidelines for early differentiation of contaminated from valid positive cultures. Arch Intern Med 1972;130:8487.
20.Finkelstein, R, Fusman, R, Oren, I, Kassis, I, Hashman, N. Clinical and epidemiologic significance of coagulase-negative staphylococci bacteremia in a tertiary care university Israeli hospital. Am J Infect Control 2002;30:2125.
21.Beekmann, SE, Diekema, DJ, Munson, EL, Doern, GV. Specificity and positive predictive value of the NNIS definition of laboratory-confirmed bloodstream infection with common skin contaminants. Presented at the 12th Annual Meeting of the Society for Healthcare Epidemiology of America; April 6-9, 2002; Salt Lake City, UT.
22.Munson, EL, Diekema, DJ, Beekmann, SE, Chapin, KC, Doern, GV. Detection and treatment of bloodstream infection: laboratory reporting and antimicrobial management. J Clin Microbiol 2002;41:495497.
23.Beekmann, SE, Diekema, DJ, Chapin, KC, Doern, GV. Effects of rapid detection of bloodstream infections on length of stay and hospital charges. J Clin Microbiol 2003;41:31193125.
24.Mirrett, S, Weinstein, MP, Reimer, LG, Wilson, ML, Relier, LB. Relevance of the number of positive bottles in determining clinical significance of coagulase-negative staphylococci in blood cultures. J Clin Microbiol 2001;39:32793281.
25.Mermel, LA, Farr, BM, Sherertz, RJ, et al.Guidelines for the management of intravascular catheter-related infections. Clin Infect Dis 2001;32:12491272.
Recommend this journal

Email your librarian or administrator to recommend adding this journal to your organisation's collection.

Infection Control & Hospital Epidemiology
  • ISSN: 0899-823X
  • EISSN: 1559-6834
  • URL: /core/journals/infection-control-and-hospital-epidemiology
Please enter your name
Please enter a valid email address
Who would you like to send this to? *


Full text views

Total number of HTML views: 0
Total number of PDF views: 9 *
Loading metrics...

Abstract views

Total abstract views: 379 *
Loading metrics...

* Views captured on Cambridge Core between September 2016 - 18th March 2018. This data will be updated every 24 hours.