Determination of disk diffusion and MIC quality control parameters for AZD2563, a novel long-acting oxazolidinone

AZD2563 is a new, long-acting oxazolidinone that possesses potent antimicrobial activity against Gram-positive organisms. This report summarizes the results of broth microdilution MIC and disk diffusion quality control (QC) investigations for AZD2563. All tests or methods (M2-A7 and M7-A5) and QC study designs (M23-A2) were those published by the National Committee for Clinical Laboratory Standards. QC strains tested against AZD2563 included: Staphylococcus aureus ATCC 25923 and ATCC 29213, Enterococcus faecalis ATCC 29212 and Streptococcus pneumoniae ATCC 49619. In the eight-center QC trial, 320 and 480 results were generated for MIC and disk diffusion tests, respectively. The selected 7-mm ranges for the two disk diffusion QC organisms contained ≥98.5% of reported results. Proposed 3 or 4 log2 dilution MIC ranges contained all reported participant results. AZD2563 disk diffusion zone diameters were generally 2-3 mm smaller than the corresponding linezolid zone diameters. In conclusion, QC ranges for AZD2563 MIC and disk diffusion methods were established and appear acceptable in preparation for the clinical trials use.