Antifungal Susceptibility Testing of Candida Isolates from the Candida Surveillance Study

Abstract

ABSTRACT Candida species are a common cause of nosocomial bloodstream infections. Recent surveillance has shown an increase in the relative proportion of infections caused by Candida glabrata , which has reduced susceptibility to fluconazole. We undertook sentinel surveillance with antifungal susceptibility testing to monitor the trends in the proportions of various Candida species causing invasive disease. Forty-one institutions participated in the Candida Surveillance Study. All isolates were submitted to a central laboratory for identification and susceptibility testing. Susceptibility testing was performed in compliance with CLSI guidelines using a custom, broth dilution, microtiter system. There were 5,900 isolates submitted for identification and antifungal susceptibility testing. The distribution of species was as follows: C. albicans , 2,567 (43.5%) isolates; C. glabrata , 1,464 (24.8%) isolates; C. parapsilosis , 1,048 (17.8%) isolates; C. tropicalis , 527 (8.9%) isolates; C. krusei , 109 (1.9%) isolates; C. lusitaniae , 76 (1.3%) isolates; and other Candida species, 109 (1.9%) isolates. Resistance to fluconazole occurred in 1.2% of C. albicans isolates, 5.9% of C. glabrata isolates, 0.3% of C. parapsilosis isolates, and 0.4% of C. tropicalis isolates. Resistance to fluconazole was highly predictive of resistance to voriconazole. Resistance to echinocandins was rarely found, occurring in only 0.2% of all isolates. The rate of fluconazole susceptibility increased significantly from 87.5% in 2005 to 97.4% in 2007. The proportion of cases of disease caused by various Candida species did not change appreciably between 2004 and 2007, and the rate of antifungal susceptibility was high.