18 Apr 2020

EUCAST panels of phenotypically defined strains

During 2020, EUCAST in collaboration with CCUG (the Culture Collection of the University of Gothenburg), and EUCAST NACs, will make available panels of organisms with phenotypically well characterized levels of susceptibility (MIC-values determined with reference broth microdilution on several occasions before and after freeze drying). Each panel will contain 10 - 25 strains of which a few strains have MICs representative of the wild type of the species, and otherwise strains with typical resistance mechanisms and phenotypically reproducible levels of susceptibility. Each panel will highlight a difficult area of susceptibility testing. They will be useful for laboratories aiming to validate the accuracy of their AST methods, for checking commercial material intended for MIC determination or susceptibility testing (the correct categorisatiopn of S, I and R) and for developers of antimicrobials and AST methods.

Recently EUCAST warned against the use of gradient tests for the determination of benzylpenicillin MICs in S. pneumoniae and before that validated the use of broth microdilution for colistin MIC determination in several species (see To be able to do this we need to invest much effort into obtaining and characterising strains and their levels of susceptibility using reference methods. In collaboration with colleagues in NACs and at the CCUG we will make selected parts of these collections publicly available.

The first panel consists of 10 Streptococcus pneumoniae with varying levels of susceptibility to betalactam agents and will shortly be made available. More information will follow on the EUCAST ( and CCUG ( websites.