European Committee on Antimicrobial Susceptibility Testing (EUCAST)

European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints are determined by assessing drugs at defined doses and considering the site of infection. Defined doses, clinical breakpoints and rationale documents are freely available on the EUCAST website.

The clinical breakpoints are defined as:

• susceptible, standard dosing regimen: there is a high likelihood of therapeutic success using a standard dosing regimen of the antimicrobial
• susceptible, increased exposure (SIE or I¹): there is a high likelihood of therapeutic success; however, success depends on increased dose, or increased exposure to the antimicrobial while considering the site of infection. Interpretation should be provided by the laboratory. Within antibiograms produced by laboratories using the EUCAST system, organisms that are SIE or I are included with the susceptible results. Dosing regimens for antimicrobials are suggested in EUCAST for this category but may differ from the dosages recommended in this guideline
• resistant: there is a high likelihood of therapeutic failure even when there is increased exposure.

Laboratories using the EUCAST breakpoints may provide comments related to dosing or combination therapy where appropriate.