Impact of the more-potent antibiotics quinupristin-dalfopristin and linezolid on outcome measure of patients with vancomycin-resistant Enterococcus bacteremia.

BACKGROUND The impact of antibiotic resistance on the clinical outcome of patients with vancomycin-resistant Enterococcus (VRE) bacteremia remains unclear. There are limited data comparing patient outcomes during the early era of vancomycin resistance with the period of more-potent antibiotic availability. METHODS A retrospective review was conducted of 113 patients with VRE bacteremia at a single institution from August 1993 to September 2005. Patients were assigned to a group on the basis of initial antibiotic choice for treatment of VRE (linezolid, quinupristin-dalfopristin, or combinations of other agents, before newer options were available). Outcome measurements were examined for the initial episode of VRE bacteremia, and multiple logistic regression analysis was performed to compare group outcomes. RESULTS Overall mortality was 37.2% (42 of 113 patients). VRE bacteremia caused or significantly contributed to death in 29 (69%) of 42 patients. Seventy-one patients were initially treated with linezolid, 20 with quinupristin-dalfopristin, and 22 with combinations of other agents. Univariate analysis indicated significantly more deaths in the quinupristin-dalfopristin group (odds ratio, 5.45; 95% confidence interval, 1.89-15.9) and in the other-agents group (odds ratio, 2.94; 95% confidence interval, 1.09-7.94) than in the linezolid group. However, after adjustment for severity of illness, treatment group was not a significant independent factor. CONCLUSION Despite the development of antimicrobial agents with greater potency against VRE, a significant change in clinical outcome was not observed. This suggests that vancomycin resistance does not significantly influence mortality and points to the continued need for prospective, randomized clinical trials.