Mechanisms of resistance to quinupristin-dalfopristin among isolates of Enterococcus faecium from animals, raw meat, and hospital patients in western Europe

Twenty-eight quinupristin-dalfopristin-resistant isolates of Enterococcus faecium from hospital patients and nonhuman sources in European countries were studied. High-level resistance (MICs, greater than or equal to 32 mu g/ml) was associated with the presence of vat(E) (satG) (14 isolates [50%]) or vat(D) (satA) (6 isolates [21%]). These genes were not detected in eight (29%) isolates with lower levels of quinupristin-dalfopristin resistance (MICs, 4 to 16 mu g/ml). This suggests the presence of further mechanisms of resistance to quinupristin-dalfopristin in E. faecium.