AST of bacteria

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 monocytogenesPasteurella 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), see EUCAST media preparation file. 


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


Broth microdilution - EUCAST reading guide v 5.0 (1 January 2024) 


Guidance on cefiderocol MIC testing - see guidance document.


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.