Evaluation of ten brands of pre-poured Mueller-Hinton agar plates for EUCAST disc diffusion testing. (November 2022)

• Record Type: Journal Article
• Authors: Åhman, Jenny; Matuschek, Erika; Kahlmeter, Gunnar
• Is Part Of: Clinical microbiology and infection. Volume 28:Number 11(2022)
• Page Start: 1499.e1
• Page End: 1499.e5
• Publication Date: 2022-11
• Subjects: Agar depth -- Antimicrobial susceptibility testing -- Cation content -- Commercial Mueller Hinton -- EUCAST methodology -- Media pH -- Quality control -- QC criteria; Medical microbiology -- Periodicals; Diagnostic microbiology -- Periodicals; Communicable diseases -- Periodicals; Infection -- Periodicals; 616.01
• DOI: 10.1016/j.cmi.2022.05.030
• Languages: English
• ISSNs: 1198-743X

Abstract

Abstract: Objectives: Mueller-Hinton agar (MHA) is recommended by EUCAST and CLSI for disc diffusion antimicrobial susceptibility testing (AST). We have previously investigated the quality of dehydrated MHA from several manufacturers. In this study, we evaluated the performance of ten commercial brands of pre-poured MHA plates. Methods: AST was performed according to EUCAST methodology and results analyzed against targets and ranges in EUCAST quality control (QC) tables. MHA plates from different brands were tested in triplicate against four non-fastidious QC strains. The agar depth and pH were measured for all products. Results: The best performance was observed for MHA from Becton Dickinson (BBL MHA II), bioMérieux (MHE agar) and Hardy Diagnostics, for which >97% of zone diameters were within QC ranges and >60% on target ±1 mm. The poorest performance was seen for plates from HiMedia (MHA and MHA no. 2), where 20% and 18% of readings were outside the QC ranges, respectively. The differences in pH and agar depth of the products were small and mostly within EUCAST specifications. Discussion: The accuracy and reproducibility of disc diffusion AST depends on standardised procedures and high-quality discs and media. The performance among ten brands of pre-poured MHA plates differed significantly. The results indicate a poorer performance for pre-poured commercial plates as compared to in-house prepared plates from dehydrated powder of corresponding brands in our previous study. Manufacturers and clinical laboratories have a shared responsibility for the quality of AST. EUCAST provides QC criteria to be used both by manufacturers and laboratories.