ISO 16256:2021

This document describes a method for testing the susceptibility to antifungal agents of yeasts, including Candida spp. and Cryptococcus neoformans, that cause infections. The reference method described here has not been used in studies of the yeast forms of dimorphic fungi, such as Blastomyces dermatitidis and/or Histoplasma capsulatum variety capsulatum. Moreover, testing filamentous fungi (moulds) introduces several additional problems in standardization not addressed by the current procedure. Those methods are beyond the scope of this document. This document describes the broth micro-dilution reference method, which can be implemented by either of two pathways. One pathway involves visual determination of MICs (CLSI method)[1][5]; the second pathway involves spectrophotometric determination of MICs (EUCAST method)[2][10]. The MIC reflects the activity of the drug under the described test conditions and can be interpreted for clinical management purposes by taking into account other factors, such as drug pharmacology or antifungal resistance mechanisms. In addition, MIC distributions can be used to define wild type or non-wild type fungal populations. Clinical interpretation of the MIC value is beyond the scope of this document; interpretive category breakpoints specific to the CLSI- and EUCAST-derived methods can be found by consulting the latest interpretive tables provided by the organizations[5][15]. Routine susceptibility testing methods or diagnostic test devices can be compared with this reference method in order to ensure comparable and reliable results for validation or registration purposes.