Quinupristin-dalfopristin versus linezolid for the treatment of vancomycin-resistant Enterococcus faecium bacteraemia: efficacy and development of resistance.

Quinupristin-dalfopristin and linezolid are widely used for the treatment of vancomycin-resistant Enterococcus faecium (VREF) infections. Increasing resistance of VREF to quinupristin-dalfopristin and linezolid is a cause for concern. To determine the efficacy of and the rate of development of resistance to quinupristin-dalfopristin and linezolid, we analyzed all episodes of clinically significant VREF bacteraemia at a tertiary-care hospital from January 2003 to June 2007. The main outcomes were rates of 30-day mortality, microbiological response, and development of resistance. Fifty-two patients were treated with quinupristin-dalfopristin and 61 were treated with linezolid. Baseline demographic and clinical characteristics were similar between the 2 groups. There were no significant between-group differences in 30-day mortality (48% in the quinupristin-dalfopristin group vs 41% in the linezolid group; p = 0.45) or microbiological response (60% vs 66%; p = 0.51). However, prolonged bacteraemia (18% of 45 evaluable cases vs 4% of 55 evaluable cases; p = 0.04) and development of resistance in blood isolates (11% vs 0%; p = 0.02) were more frequently observed in the quinupristin-dalfopristin group than in the linezolid group. There was no significant difference between the efficacy of quinupristin-dalfopristin and linezolid. However, prolonged bacteraemia and the development of resistance were more common in quinupristin-dalfopristin-treated patients.