Antifungal susceptibility testing, reporting and antifungal resistance: current status

Abstract

Appropriate early treatment is crucial for prognosis in invasive fungal infections (IFIs). Antimicrobial susceptibility has generally an important role for treatment options and clinical outcome. “The European Committee on Antimicrobial Susceptibility Testing (EUCAST)” and “The Clinical and Laboratory Standards Institute (CLSI)” defined standard procedures and recommendations on interpretations of minimum inhibitory concentrations (MICs). However, they do not include epidemiological cut-off values (ECOFFs) and/or clinical breakpoints (CBPs) for every fungi and antifungal agent, so only MIC values can be shared to guide clinicians. Microbiological resistance is determined by interpreting the in vitro MICs with comparison of CBPs. There are many mechanisms that lead to antifungal resistance (AFR). There are increasing trends in fluconazole and echinocandin resistance for yeasts and in triazole resistance for molds. Although clinical reflections of these high MICs are sometimes very obvious, there is insufficient data to show in every fungi. Clinical resistance is the event that an infection does not resolve for various reasons despite appropriate treatment, and can be attributed to many reasons. Thus, every infection caused by susceptible organism is not always successfully treated, every infection caused by resistant organism is not always a failure. The aim of this review is to create an overall perspective to antifungal susceptibility testing and notify current condition of AFR worldwide and in our country. As IFIs show epidemiological changes and become more frequently recognized, studies on the use of antifungals have also increased, while AFR has come to the fore as one of the current problems. With Candida auris, it is clear that it is necessary to put an end to the relative “ignorance of fungi”.