Echinocandin Susceptibility Testing of CandidaIsolates Collected during a 1-Year Period in Sweden

ABSTRACTThe susceptibilities of Candidaisolates to the echinocandins anidulafungin, caspofungin, and micafungin were determined by using the recently revised CLSI breakpoints and Etest on 238 clinical bloodstream Candidaisolates collected between September 2005 and August 2006. The isolates represent approximately 95% of all non-albicans Candidabloodstream infections and one-third of Candida albicansbloodstream infections during this 1-year period in Sweden. The collection included 81 C. albicans, 81 C. glabrata, 36 C. parapsilosis, 14 C. dubliniensis, 8 C. tropicalis, 8 C. lusitaniae, 5 C. krusei, 2 C. guilliermondiiand 2 C. inconspicuaisolates as well as 1 C. pelliculosaisolate. The MICs were largely consistent with the global epidemiology of bloodstream Candidaisolates. All C. albicansand C. glabrataisolates were susceptible to all 3 echinocandins (MIC = 0.016 µg/ml in all instances). Resistance (MIC = 8 µg/ml) to anidulafungin alone was observed for 4 (11.1%) C. parapsilosisisolates and for 1/2 C. guilliermondiiisolates. Intermediate susceptibility to caspofungin alone was observed for 2/5 C. kruseiisolates. One of the eight C. tropicalisisolates was classified as being intermediately susceptible to micafungin (MIC, 0.5 µg/ml) and as being resistant to anidulafungin and caspofungin (MIC = 1 µg/ml). This isolate harbored a heterozygous FKS1hot spot mutation (S80P) known to confer echinocandin resistance. This first study to apply the revised CLSI breakpoints for Etest endpoints showed that the breakpoints worked successfully in detecting an isolate with a hot spot mutation. Acquired echinocandin resistance is rare in Sweden. Echinocandin MICs against C. parapsilosisand C. guilliermondiiwere lowest for micafungin.