Several microbroth dilution methods have been developed by the Clinical and Laboratory Standards Institute (CLSI) and the European Committee on Antimicrobial Susceptibility Testing (EUCAST) to test the susceptibility of fermentative yeasts and moulds to several antifungal drugs and to determine breakpoints. Several parameters differ between the methods including a higher inoculum size with the EUCAST method. They have been shown to generate concordant data. Both methods have allowed determining the spectrum of activity of commercialized and non-commercialized antifungal drugs on a wide variety of yeasts and moulds. Breakpoints have only been defined for fluconazole and voriconazole on fermentative yeasts using the EUCAST method. Probably because the microbroth dilution EUCAST method has been implemented more recently than CLSI one, publications of correlations between in vivo and in vitro results are scare using the former. Based on the antifungal susceptibility testing results generated at the French National Reference Center for Mycoses and Antifungals using the EUCAST methods and thanks to the clinical and epidemiological data associated with each isolate tested, we have been able to show (1) cross-reduced susceptibility between azoles, and between caspofungin and micafungin against yeasts (2) demonstrate that caspofungin MICs >=0.5 Âµg/ml in AM3 medium correlate with FKS mutation for Candida spp. (3) show that prior exposure to fluconazole or caspofungin lead to fungemia caused by isolates with a significantly higher fluconazole or caspofungin MIC, respectively, or to emergence of species with decreased susceptibility to the respective drugs; and (4) demonstrate the in vivo/in vitro correlation for caspofungin after exploring several episodes of treatment failure These results suggests that antifungal susceptibility testing using the EUCAST method together with species identification are useful for the management of invasive fungal infections especially in the case where prior exposure to antifungal drugs is known.
Full conference title:
17th International Society for Human and Animal Mycology
- ISHAM 17th (2009)