Antifungal susceptibility testing ? available methods and interpretative difficulties

The introduction of new antifungal agents and recent reports on resistance emerging during treatment have highlighted the requirement for in vitro accurate susceptibility testing of fungi. Invasive fungal infections constitute an increasing clinical problem in immunocompromised patients. Furthermore, the spectrum of fungal pathogens is growing. The available therapeutic options are relatively limited, particularly when pathogens are resistant to antifungals. The most important role of antifungal susceptibility testing is detection of fungal resistance, both intrinsic and acquired resistance are encountered. Various susceptibility testing procedures have been proposed, including macrodilution and microdilution, agar diffusion and disk diffusion. Clinical breakpoints for Candida spp. and several antifungals are established by EUCAST (European Committee on Antimicrobial Susceptibility Testing) and CLSI (Clinical Laboratory Standards Institute), and are still subjected to reassessment. Early recognition of infections caused by resistant pathogens is highly warranted to optimize treatment and patient outcome.