Revision of linezolid disk diffusion quality control guidelines for testing Staphylococcus aureus ATCC 25923: An independent seven-laboratory trial

Abstract

The accuracy of the published disk diffusion quality control (QC) range for linezolid for Staphylococcus aureus ATCC 25923 has been reported to be problematic, prompting a multicenter study to determine if revision was necessary. Five out of seven laboratories reported values outside the current QC range. Three participants had significant (13.3-60.0%) 'unacceptable' results with zones smaller than the established range. Overall, a range of 21-32 mm was shown (82.4% within the NCCLS published range). A revision (25-31 mm; 95.7% of results) of the QC range is necessary when testing S. aureus ATCC 25923 against linezolid.