ITRACONAZOLE SUSCEPTIBILITIES OF FLUCONAZOLE SUSCEPTIBLE AND RESISTANT ISOLATES OF 5 CANDIDA SPECIES

The in-vitro susceptibilities of 1380 isolates of five Candida species were determined in order to establish whether isolates resistant to fluconazole were cross-resistant to itraconazole. IC50 values were determined by a broth microdilution method. 690 Candida albicans isolates, seven Candida glabrata isolates, seven Candida krusei isolates, 120 Candida parapsilosis isolates and 37 Candida tropicalis isolates were susceptible to both fluconazole (IC50 less than or equal to 32 mg/L) and itraconazole (IC50 less than or equal to 4 mg/L). Twenty eight of 160 C. albicans isolates (17.5%), 180 of 293 C. glabrata isolates (61.4%), six of 48 C. krusei isolates (12.5%), and 10 of 18 C. tropicalis isolates (55.5%) resistant to fluconazole (IC(50)greater than or equal to 64mg/L) were also resistant to itraconazole (IC50 greater than or equal to 8 mg/L). In contrast, drug-specific resistance to itraconazole was not observed in any of the isolates tested. However, the itraconazole IC(50)s for fluconazole susceptible isolates were lower than those for fluconazole resistant isolates, which suggests that patients who fail fluconazole treatment might require itraconazole at higher dosages than usual.