In vitro activity of linezolid & quinupristin/dalfopristin against Gram-positive cocci.

BACKGROUND & OBJECTIVES Since the incidence of vancomycin- and methicillin-resistant Gram-positive infections continue to increase, novel antimicrobials such as linezolid and streptogramin may provide new options to treat patients. The aim of this study was to investigate in vitro susceptibility of Enterococcus faecium resistant to glycopeptides, coagulase negative staphylococci and S. aureus resistant to methicillin isolated mainly from blood and also rectal swab cultures of patients against quinupristin/dalfopristin and linezolid. METHODS The in vitro susceptibility to linezolid and quinupristin/dalfopristin for a total of 332 isolates of Gram-positive cocci [127 methicillin-resistant Staphylococcus aureus, 109 methicillin-resistant coagulase negative staphylococci (71 S. epidermidis, 38 S. haemolyticus) and 96 vanA genotype vancomycin-resistant Enterococcus faecium] was investigated by E test. RESULTS All MRSA and MRCoNS isolates were susceptible to linezolid (MICs < 4.0 mg/l). Ninety per cent of VRE isolates were inhibited by linezolid at concentration of 2.0 mg/l and presented similar activities to quinupristin/dalfopristin. MICs for quinupristin/dalfopristin against staphylococci were also low (MIC(90) = 1.0 mg/l for both MRSA and MRCoNS isolates). INTERPRETATION & CONCLUSION The results of the present study demonstrated that quinupristin/ dalfopristin and linezolid, have good in vitro activity against MRSA, MRCoNS and vancomycin resistant E. faecium in Turkey. These drugs could be promising therapeutic options in an era of rapidly growing antibiotic resistance in all parts of world.