Antimicrobial susceptibility testing of bacteria

Antimicrobial susceptibility testing

Antimicrobial susceptibility testing is performed with phenotypic or genotypic methods. The basis of phenotypic methods is the minimum inhibitory concentration (MIC). Clinical MIC breakpoints determine whether the organism is categorised as susceptible, intermediate or resistant to the agent in question. Other methods should be calibrated to reference MIC methods.


Users of EUCAST breakpoints should use the EUCAST disk diffusion method or other susceptibility testing systems calibrated to EUCAST breakpoints and terminology in accordance with EUCAST breakpoint tables.
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  • Media preparation
    On how to prepare media for MIC and disk testing
  • MIC determination of nonfastidious and fastidious organisms
    Broth microdilution methodology according to ISO and EUCAST
  • Disk diffusion methodology
    Detailed description of the EUCAST disk diffusion test
  • Disk diffusion implementation
    Guidance documents on how to implement the disk diffusion test
  • Compliance of manufacturers
    Compliance of manufacturers of susceptibility testing products with EUCAST guidelines
  • Breakpoint tables
    Current MIC and zone diameter breakpoint tables
  • QC tables
    Current tables of MIC and zone diameter ranges for quality control strains
  • Calibration and validation
    Data used in the development and calibration of EUCAST disk diffusion breakpoints
  • Guidance documents
    Guidance notes on specific susceptibility testing issues
  • Projects and data submission
  • Invitations to laboratories to participate in projects to develop EUCAST methods
  • Previous breakpoints and QC tables
    Earlier versions of breakpoint and QC tables