[Antifungal susceptibility among the isolates of yeast from the University Hospital of the Ryukyus].

During the period from 1999 to 2003, A total of 2,255 isolates of yeast from the patients of the University Hospital of the Ryukyus were determined for their antifungal susceptibilities by the ASTY (Kyokuto Pharmaceutical Industrial Co., Ltd., Tokyo) colorimetric microdilution testing. The isolates included 1,576 strains of Candida albicans, 409 of C. glabrata, 69 of C. tropicalis, 60 of C. parapsilosis and 141 of other Candida species. A high and uniform antifungal activity of amphotericin B against all the members of Candida was demonstrated with the most minimum inhibitory concentrations (MICs) ranging between 0.25 to 2.0 microg/ml. The MICs obtained from a nearly half of the isolates included against flucytosine distributed < or = 0.125 microg/ml, but 65 (2.9%) and 43 (1.9%) isolates were interpreted as being resistant and intermediate, respectively. The activity of fluconazole markedly varied by species. The resistant ratios of C. albicans and C. parapsilosis were 0.9% and 1.7%, whereas those of C. tropicalis and C. glabrata were estimated as being 40.6% and 13.7%, respectively. The activities of miconazole and micafungin were the most potent with MICs50, 0.125 and 0.06 microg/ml. However, the MICs of C. parapsilosis against miconazole and those of C. glabrata against micafungin were significantly higher when compared to those of C. albicans. By this study, it became apparent that the activities of the presently available antifungal agents were mostly similar for the time and place, but the susceptibilities of the agents among Candida species were markedly different, particularly against azole derivatives. With this, it is necessary for clinical microbiology laboratories to determine antifungal susceptibility for the isolates of yeast and to continuously monitor the effectiveness of each antifungal agent.