[In vitro susceptibility to linezolid in methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus strains].

There has been a dramatic increase in the number of infections caused by methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) worldwide. Linezolid which is one of the first oxazolidinones in clinical use, has bacteriostatic activity on gram-positive bacteria including MRSA and VRE. The aim of this study was to investigate the in vitro susceptibilities of MRSA and VRE clinical isolates to linezolid. A total of 100 MRSA strains isolated from clinical specimens as infectious agents (96 blood, 2 pleural fluid, 1 peritoneal fluid, 1 joint fluid isolates), and 101 VRE (Enterococcus faecium) strains isolated from clinical specimens as colonizing or infectious agents (79 rectal swabs, 11 blood, 3 catheter, 3 peritoneal fluid, 3 urine, 2 wound isolates) in Microbiology Laboratory of Uludag University Medical Faculty Hospital, Turkey, were included to the study. In vitro linezolid activity has been searched by E-test method and all of the isolates were found susceptible to linezolid. Linezolid minimal inhibitory concentration (MIC) ranged for MRSA and VRE between 0.25-3 microg/mL and 0.25-2 microg/mL, respectively. Linezolid MIC50 and MIC90 values for MRSA were 1.5 microg/mL and 2 microg/mL, respectively, while for VRE these values were 0.75 microg/mL and 1.5 microg/mL, respectively. Our results were in parallel with the data of other national and international studies, emphasizing that linezolid is a new and effective choice in treatment of infections caused by resistant gram-positive bacteria.