National surveillance of species distribution in blood isolates of Candida species in Japan and their susceptibility to six antifungal agents including voriconazole and micafungin

Abstract

Objectives: The aim of this study was to evaluate species distribution and antifungal susceptibility of Candida blood isolates in Japan. Methods: In a 1 year surveillance programme, 535 Candida blood isolates were collected. Identification of species was followed by examination with the broth microdilution method, as described in NCCLS M27-A2, of antifungal susceptibility to six agents, including voriconazole and micafungin, with readings after 24 and 48 h of incubation. Results: The overall species distribution was: 41% Candida albicans, 23% Candida parapsilosis, 18% Candida glabrata, 12% Candida tropicalis and 2% Candida krusei. The concentrations of fluconazole necessary to inhibit 90% of the isolates (MIC₉₀) at 24/48 h were 0.25/1 mg/L for C. albicans, 0.5/2 mg/L for C. parapsilosis, 4/32 mg/L for C. glabrata and 4/>128 mg/L for C. tropicalis. Percentages of fluconazole resistance were 1.8% for C. albicans, 0.8% for C. parapsilosis, 5.2% for C. glabrata and 3.2% for C. tropicalis, taking the tendency of trailing growth of C. tropicalis into account. MIC₉₀ of voriconazole was 0.5 mg/L, although 35% of isolates less susceptible (≥16 mg/L) to fluconazole showed resistance (≥2 mg/L). Micafungin was very active against all species (MIC₉₀, 0.03 mg/L) except for C. parapsilosis (MIC₉₀, 2 mg/L). Conclusions: These data suggest that, in Japan, the species distribution of Candida bloodstream infections and the fluconazole resistance rate are similar to those reported previously in North America and Europe. Voriconazole and micafungin appear to have strong in vitro activity against Candida blood isolates, although continuing surveillance and further clinical research are needed.