Antifungal susceptibility testing for yeasts: how, when and why, according to the new EUCAST guidelines

Antifungal susceptibility testing of yeasts and the development of interpretive breakpoints are nowadays very important topics both for the increasing incidence of invasive mycoses and number of available antifungal drugs and for the appearance of acquired resistance. The Subcommittee on Antifungal Susceptibility Testing (AFST) of the European Committee on Antibiotic Susceptibility Testing (EUCAST) has recently released both the operative standards to evaluate the fermenting yeasts susceptibility against antimycotic drugs and the breakpoints for infections due to some Candida species and for some of the available antifungals. Antifungal susceptibility testing is mandatory on a routine base for: 1. therapeutic failure, 2. breakthrough fungemias, 3. on yeasts isolated from patients who recently received prophylactic antifungal treatments, and 4. when the deep-seated infection is due to less common yeasts, with an unknown susceptibility pattern. The Medical Mycology Committee (CoSM) of the Italian Society of Clinical Microbiologists (AMCLI) adopted the interpretive breakpoints of both CLSI and EUCAST. The operating procedure for antifungal susceptibility testing according to EUCAST is supported by the recommendation to use, when clinically necessary, validated commercial methods (Vitek2, Sensititre, E-test). Finally, the CoSM reports the recommendations for a correct management of antifungal susceptibility testing