Epidemiology and significance of coagulase-negative staphylococci isolated in blood cultures from critically ill adult patients.

BACKGROUND Little published data are available on the epidemiology and significance of coagulase-negative staphylococci (CoNS) in blood culture isolates among critically ill adult patients. OBJECTIVES To describe the epidemiology and frequency of CoNS blood culture isolates in critically ill adults, and investigate the association between time to positivity (TTP) of blood cultures and number of culture-positive bottles with organ dysfunction and mortality. DESIGN, SETTING AND PARTICIPANTS A retrospective chart audit in the intensive care unit of a tertiary hospital comprising all patients who had positive blood cultures for CoNS in 2009. MAIN OUTCOME MEASURES TTP, number of culture-positive bottles, Sequential Organ Failure Assessment (SOFA) scores, resolution of fever and white cell response and inotrope requirement, length of stay in ICU and mortality. RESULTS In 2009, there were 1514 and 109 positive blood culture sets for the hospital and ICU patients, respectively. Of these, 515 sets from patients outside the ICU (34% of all hospital positive blood cultures) and 54 from the ICU (49.5% of all ICU positive blood cultures) were positive for CoNS. Patients with TTP ≤24 hours had higher organ failure scores by 0.9 (95% CI, 0-3.4; P = 0.052). There was a trend towards an association between increased 28-day mortality and TTP ≤24 hours (7/22 v 3/32; P = 0.071). There was no significant correlation between number of bottles positive for culture and mortality, length of stay, SOFA score, resolution of fever, white cell response, and inotrope requirement. CONCLUSIONS Early TTP of blood cultures with CoNS may be associated with poorer outcome and may be a marker of true infection. Given the relatively high frequency of this microbiological problem, larger prospective observational studies are required to more clearly define the significance of a CoNS blood culture isolates in critically ill adult patients.