In vitro evaluation of AZD2563, a novel oxazolidinone, against 603 recent staphylococcal isolates

AZD2563, a novel oxazolidinone, and a selection of comparator drugs that included linezolid, erythromycin, clindamycin, quinolones, and gentamicin were tested against 384 Staphylococcus aureus (176 oxacillin-resistant S. aureus [ORSA]) and 219 coagulase-negative staphylococci (CoNS; 162 oxacillin resistant) by reference microdillution (all strains) and agar dilution (30 strains) methods. The following results were noted for AZD2563. (Note that, for comparison only, a breakpoint of less than or equal to4 mug/ml [the breakpoint of linezolid] was used for this study, although a susceptibility breakpoint for AZD2563 has not been determined.) For S. aureus, the MIC at which 50% of the isolates tested are inhibited (MIC50) was 1 mug/ml, the MIC90 was 2 mug/ml, and the percent susceptibility was 100%. For CoNS, the MIC50 was 0.5 mug/ml, the MIC90 was 1 mug/ml, and the percent susceptibility was 100%. ORSA and OR-CoNS strains were equally inhibited by AZD2563 and linezolid. AZD2563 demonstrated anti staphylococcal activity comparable to that of linezolid.