Alterations in GyrA and ParC Associated with Fluoroquinolone Resistance in Enterococcus faecium

High-level quinolone resistance in Enterococcus faecium was associated with mutations in both gyrA and parC genes in 10 of 11 resistant strains. One low-level resistant strain without such mutations may instead possess an efflux mechanism or alterations in the other subunits of the gyrase or topoisomerase IV genes. These findings are similar to those for other gram-positive bacteria, such as Enterococcus faecalis.