OBJECTIVE: To examine the relationship between the isolation of coagulase-negative Staphylococcus in blood cultures and acute phase markers of inflammation.METHODS: The present study was a prospective observational analysis conducted at three medical/surgical intensive care units (ICUs) involving adult patients with an expected ICU stay of more than 24 h duration.RESULTS: Of the 598 patients enrolled, 573 developed suspected bloodstream infection and 434 (72.6%) had blood cultures sent 24 h after ICU admission; 142 were excluded due to positive cultures from other sites. Of the remaining 292 patients, 31 (10.7%) grew coagulase-negative Staphylococcus, 59 (20.2%) grew known pathogenic organisms and 202 (69.2%) did not grow any organisms in their blood cultures. Twenty-five patients without suspicion of infection served as the control group. Interleukin (IL)-6, procalcitonin (PCT) and C-reactive protein (CRP) levels were highest among the known pathogen group (IL-6 271.8 U/L, PCT 4.6 U/L and CRP 164 mg/L), were similar between the coagulase-negative Staphylococcus and negative culture groups (IL-6 67.0 U/L versus 61.4 U/L [P=1.00]; PCT 1.0 U/L versus 0.9 U/L [P=0.80]; and CRP 110 mg/L versus 103 mg/L [P=0.75]), and were lowest in the control group (IL-6 31.0 U/L, PCT 0.2 U/L and CRP 41.0 mg/L). In the coagulase-negative Staphylococcus group, patients who died by day 28 had increased inflammatory bio-marker levels compared with survivors, although the differences were not statistically significant.CONCLUSIONS: Coagulase-negative Staphylococcus isolated from blood cultures were associated with lower levels of inflammation compared with bloodstream infections due to known pathogens and were comparable with levels in patients with negative cultures.