SUSCEPTIBILITIES OF NORWEGIAN CANDIDA-ALBICANS STRAINS TO FLUCONAZOLE- EMERGENCE OF RESISTANCE

All Candida albicans isolates in Norwegian microbiological laboratorie s in 1991 judged clinically important (except vaginal isolates) were c ollected. The isolates were tested for susceptibility to fluconazole w ith an agar dilution test and a commercially available agar diffusion test. A total of 212 strains (95%) were susceptible to fluconazole, an d MICs for most of the strains (92%) were less-than-or-equal-to 1.56 m ug/ml. The agar diffusion test using a 15-mug tablet and a 48-h incuba tion period separated resistant from susceptible strains with a wide m argin. The only exception was a strain for which the MIC was 6.25 mug/ ml. The difference in zone size between the resistant and the suscepti ble populations of strains was 11 mm. Accordingly, it appears that the agar diffusion test is an appropriate method for detecting fluconazol e resistance. The 12 fluconazole-resistant isolates originated from ei ght AIDS patients with oral or esophageal Candida infections. Seven of the patients had been given fluconazole for 1 month or more, often as self medication. Four had infections that were clinically resistant t o fluconazole; one additional patient responded only when the dose was increased. All isolates recovered from these patients were analyzed b y multilocus enzyme electrophoresis. The 12 C. albicans isolates belon ged to five electrophoretic types, but three of four patients attendin g one hospital had isolates belonging to one electrophoretic type. One possible explanation for this finding could be that a nosocomial spre ad of resistant strains has occurred.