MIC Determination of non-fastidious and fastidious organisms

The EUCAST recommendations for MIC determination for non-fastidious organisms are in complete agreement with the recommendations from the International Standards Organisation (ISO). 

For fastidious organisms (streptococci including S. pneumoniae, H. influenzae, Moraxella catharrhalis, Listeria monocytogenes, Pasteurella spp, Kingella kingae, Aerococcus spp, Campylobacter spp, and others), EUCAST recommends the same methodology but with the use of MH-F broth (MH broth with lysed horse blood and beta-NAD).

Media preparation - see separate guidance (agar and broth for non-fastidious and fastidious organisms). 

For previous versions of documents - see the document archive.

There are a number of commercially available surrogate MIC determination methods, such as commercial broth microdilution methods, gradient tests, semi-automated devices, etc. It is the responsibility of the manufacturer to guarantee the accuracy of their systems but it is the responsibility of the user to quality control the results obtained with these systems. We also refer the users to the EUCAST Warnings page where some of these products listed. 

ISO documents of relevance to antimicrobial susceptibility testing

These documents are available for purchase from ISO or national standards organisations. You are advised to check costs as they may differ substantially between suppliers.

ISO 20776-1 (2019)
Susceptibility testing of infectious agents and evaluation of performance of antimicrobial susceptibility test devices - Part 1: Broth micro-dilution reference method for testing the in vitro activity of antimicrobial agents against rapidly growing aerobic bacteria involved in infectious diseases.

ISO 20776-2 (2021)
Clinical laboratory testing and in vitro diagnostic test systems - Susceptibility testing of infectious agents and evaluation of performance of antimicrobial susceptibility test devices - Part 2: Evaluation of performance of antimicrobial susceptibility test devices against reference broth micro-dilution.