Abstract

In 2002, the European Committee on Antimicrobial Susceptibility Testing (EUCAST) decided to collect large numbers of international minimum inhibitory concentration (MIC) distributions for all bacterial species and agents. To complete the standardisation and harmonisation of clinical breakpoints across Europe, EUCAST needed to identify the “normal” prior to defining the “abnormal”. It was noted that provided the methodology used was equivalent, organisms for well-defined species without acquired resistance behaved identically irrespective of origin. EUCAST coined the terms “wildtype” MIC distributions and “epidemiological cut-off value” (based on phenotypic traits only and abbreviated WT and ECOFF, respectively) [1].