02.02.2023

The quality of material for EUCAST disk diffusion

EUCAST has investigated and reported on the quality of materials used for EUCAST disk diffusion antimicrobial susceptibility testing (AST); Mueller-Hinton agar, Pre-poured commercial Mueller-Hinton plates and antibiotic disks. The publications from these investigations are available from the EUCAST website (antibiotic disk quality, MH powder quality, the quality of pre-poured MH plates). In most, but not all, instances manufacturers have taken such reports seriously and amended and improved internal production quality control. A regular or repeated assessment of the quality of material for AST is beyond the scope and capability of EUCAST and rests with the manufacturer and in the end with the end-user of the material. The assessments performed by the EUCAST Development Laboratory will assist manufacturers and users to check and improve quality but cannot serve as a "quality stamp". EUCAST does not recommend specific manufacturers or brands of media and disks, although on occasion we will warn against products found to be of insufficient quality. Again, we remind manufacturers and users to aim for the target values available in EUCAST QC tables and to use ranges (most commonly of +/- one MIC dilution step and for zone diameters +/-3 mm) only to set limits for unavoidable random variation in both MIC and disk diffusion testing.