ANTIFUNGAL DRUG SUSCEPTIBILITIES OF ORAL CANDIDA-DUBLINIENSIS ISOLATES FROM HUMAN-IMMUNODEFICIENCY-VIRUS (HIV)-INFECTED AND NON-HIV-INFECTED SUBJECTS AND GENERATION OF STABLE FLUCONAZOLE-RESISTANT DERIVATIVES IN-VITRO

Candida dubliniensis is a recently described species of Candida associ ated,vith oral candidiasis in human immunodeficiency virus (HIV)-infec ted individuals. Nineteen oral isolates of C. dubliniensis recovered f rom 10 HIV-positive and 4 HIV-negative individuals and one vaginal iso late from an additional HIV-negative subject were assessed for flucona zole susceptibility by broth microdilution (BMD), hyphal elongation as sessment, and Etest, The susceptibilities of these 20 isolates to itra conazole and amphotericin B and of 10 isolates to ketoconazole were al so determined by BMD only, Sixteen of the C. dubliniensis isolates wer e susceptible to fluconazole (MIC range, 0.125 to 1.0 mu g ml(-1)), an d four (recovered from two AIDS patients) were fluconazole resistant ( MIC range, 8 to 32 mu g ml(-1)). Fluconazole susceptibility data obtai ned by hyphal elongation assessment correlated well with results obtai ned by BMD, but the corresponding Etest MIC results were one to four t imes higher, All of the isolates tested were found to be sensitive to itraconazole, ketoconazole, and amphotericin B, Sequential exposure of two fluconazole-sensitive (MIC, 0.5 mu g ml(-1)) C. dubliniensis isol ates to increasing concentrations of fluconazole in agar medium result ed in the recovery of derivatives which expressed a stable fluconazole -resistant phenotype (BMD-determined MIC range, 16 to 64 mu g ml(-1)), even after a minimum of 10 consecutive subcultures on drug-free mediu m and following prolonged storage at -70 degrees C, The clonal relatio nship between the parental isolates and their respective fluconazole-r esistant derivatives was confirmed by genomic DNA fingerprinting and k aryotype analysis. The results of this study demonstrate that C. dubli niensis is inherently susceptible to commonly used antifungal drugs, t hat fluconazole resistance does occur in clinical isolates, and that s table fluconazole resistance can be readily induced in vitro following exposure to the drug.