Introduction to the Revised International Guidelines on Breakpoints for Antimicrobial Susceptibility Testing

Clinical and Laboratory Standards Institute (CLSI) M100 ‘Performance Standards for Antimicrobial Susceptibility Testing (AST)’ and the European Committee on AST (EUCAST) ‘Breakpoint tables for interpretation of MICs and zone diameters’ guidelines for conducting and interpreting AST are revised yearly. The 2023 CLSI guideline introduces selective and cascade reporting methods for antibacterial agents as a part of strengthening antibiotic stewardship and changes in breakpoints for aminoglycoside (AG) in Enterobacterales and AG and piperacillin in Pseudomonas aeruginosa. Main changes in EUCAST include revised breakpoints for aminopenicillins in Enterobacterales, and detailed criteria reflecting the clinical situation and antibacterial agent administration method.