Echinocandin susceptibility testing of Candida isolates collected during a 1-year period in Sweden

Abstract

The susceptibilities of Candida isolates to the echinocandins anidulafungin, caspofungin, and micafungin were determined by using the recently revised CLSI breakpoints and Etest on 238 clinical bloodstream Candida isolates collected between September 2005 and August 2006. The isolates represent approximately 95% of all non-albicans Candida bloodstream infections and one-third of Candida albicans bloodstream 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. guilliermondii and 2 C. inconspicua isolates as well as 1 C. pelliculosa isolate. The MICs were largely consistent with the global epidemiology of bloodstream Candida isolates. All C. albicans and C. glabrata isolates 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. parapsilosis isolates and for 1/2 C. guilliermondii isolates. Intermediate susceptibility to caspofungin alone was observed for 2/5 C. krusei isolates. One of the eight C. tropicalis isolates 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 FKS1 hot 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. parapsilosis and C. guilliermondii were lowest for micafungin.