The current role of the reference procedures by CLSI and EUCAST in the detection of resistance to antifungal agents in vitro.

The role of antifungal susceptibility testing (AFST) reference procedures seems to be restricted to a number of uses and to being performed in reference laboratories, since several automated or semi-automated commercial systems and methods based on the disk diffusion technique were developed. These methods have been shown to have a high correlation with reference procedures and provide simple, flexible and affordable alternative susceptibility testing procedures for use in the clinical laboratory. One of the most important current tasks of the reference procedures is establishing antifungal breakpoints to interpret the AFST results. The procedure by the Clinical Laboratory Standards Institute to develop MIC interpretative breakpoints is based on the analysis of the MIC distribution and the clinical relationship between MIC values and efficacy. The emergence of resistance to licensed antifungal agents and the description of therapeutic failures related to high MIC values underscore the need for continued surveillance. The surveillance should be carried out using the reference procedures and taking into account the breakpoints established by the expert committees of the Clinical Laboratory Standards Institute and European Committee on Antimicrobial Susceptibility Testing. In addition, reference procedures of AFST provide a standard basis from which new AFST methods and techniques can be developed and compared. The evaluation of new antifungal agents and the susceptibility profile of rare and emerging species should also be performed by the reference techniques. Modifications of the reference procedures can even be used to test fastidious microorganisms for which routine techniques are not useful.