EUCAST and CLSI: How to Assess in Vitro Susceptibility and Clinical Resistance

There are two different approved reference procedures based on microdilution techniques for antifungal susceptibility testing (AFST) of fungal species, the CLSI and the EUCAST procedures. Although there have always been some methodological differences between them, AFST results are comparable. In addition, current breakpoints values of antifungal compounds to interpret AFST results set by both institutions are very similar with some exceptions. Experts advised AFST should be done with validated commercial techniques for a routine daily practice and discrepant results should be confirmed by reference procedures particularly for isolates with borderline/resistant MIC values. Reference methods by EUCAST and CLSI should be also used in periodical epidemiological studies, to evaluate new antifungal agents, new methods of AFST and to know the susceptibility profile of rare and emerging fungal species.