In vitro susceptibility of a large collection of Candida Strains against fluconazole and voriconazole by using the CLSI disk diffusion assay

Abstract

We evaluated all Candida spp. isolates obtained from patients admitted to two tertiary care hospitals between 1999 and 2003 in the city of São Paulo, Brazil. The in vitro activities of fluconazole (FCZ) and voriconazole were determined by the agar disk diffusion test using the Clinical and Laboratory Standards Institute M44-A guidelines. The inhibition zone diameters were read and interpreted automatically by the BIOMIC(®) image-analysis plate reader system. We tested a total of 4,625 strains, including 2,393 strains of C. albicans (51.7%), 658 of C. tropicalis (14.2%), 503 of C. glabrata (10.9%), 495 of C. parapsilosis (10.7%), 292 of C. rugosa (6.3%), 195 of C. guilliermondii (4.2%) and 89 of other Candida species (2.0%). Only 2.0% of the strains tested were classified as dose-dependent susceptible (DDS), and 5.8% of them were resistant to FCZ. The resistance or DDS to fluconazole was verified mainly among C. glabrata (7.8%), C. krusei (67.9%) and C. rugosa (65.1%). Voriconazole exhibited better activity in vitro than fluconazole, even in isolates fluconazole resistant. The resistance of fluconazole and voriconazole did not increase in the isolates of Candida spp. during the evaluated period.