Related Experiment Video
Updated: Jun 8, 2025
One-day Workflow Scheme for Bacterial Pathogen Detection and Antimicrobial Resistance Testing from Blood Cultures
Published on: July 9, 2012
Selection and evaluation of suitable quality control strains for meropenem antimicrobial susceptibility testing
Junichi Hirayama1, Kotaro Aoki2, Kohji Komori3
1Department of Microbiology and Infection Control and Prevention, Toho University Graduate School of Medicine, Tokyo, Japan; Department of Medical Affairs, bioMérieux Japan Ltd, Tokyo, Japan.
Background:
Quality control (QC) of carbapenem susceptibility testing for Gram-negative bacteria faces challenges due to limited measuring ranges and the lack of suitable QC strains. This study aimed to select and evaluate QC strains for meropenem antimicrobial susceptibility testing (AST) through a pilot external quality assessment (EQA).
Methods:
Candidate QC strains for meropenem AST were selected based on primary AST data and genomic information from the Japan Antimicrobial Resistant Bacterial Bank. Phenotype stability was verified through serial passaging and MIC comparison with original strains. The validated broth microdilution method was used to determine the target MIC value in a pilot EQA involving 47 clinical laboratories in Japan using ten different AST methods.
Results:
Two strains, Citrobacter freundii JBBDAJB-19-0032 (Strain-A) and Enterobacter hormaechei subsp. steigerwaltii JBEBAAB-19-0102 (Strain-B), both carrying blaIMP-1, were selected as candidate QC strains. The meropenem MICs for Strain-A and Strain-B were 4 mg/L and 2 mg/L, respectively. In the pilot EQA, 43 laboratories reported appropriate results for Strain-A and 40 laboratories reported appropriate results for Strain-B. The MIC range was 2-8 mg/L for Strain-A and 1-4 mg/L for Strain-B. However, 19 and 12 laboratories, respectively, reported out-of-range MICs using AST plates on the MicroScan WalkAway. Inappropriate results were reported by four and seven laboratories, respectively, using common methods for Strain-A and Strain-B, respectively.
Conclusions:
The candidate QC strains selected for this study are suitable for meropenem AST EQA, except when the measuring range of certain methods does not match their QC range.
