DNA subtypes and fluconazole susceptibilities of candida albicans isolates from the oral cavities of patients with AIDS

Sixty-two Candida albicans isolates from the oral cavities of 28 patients with AIDS who were receiving fluconazole therapy were typed by restriction endonuclease analysis followed by pulsed-field gel electrophoresis; these isolates were then tested for fluconazole susceptibility by a standard broth dilution method. Sequential isolates (range, 2–4) were evaluated for 22 patients; only one isolate was evaluated for six patients. DNA subtyping revealed a total of 37 different DNA subtypes. Twelve (54.5%) of 22 patients with multiple episodes of oropharyngeal candidiasis were infected with a single DNA subtype throughout the observation period. Ten (45.5%) of 22 patients with multiple episodes of oropharyngeal candidiasis were infected with two or three DNA subtypes during the observation period. In vitro susceptibility tests revealed that MICs of fluconazole ranged from ≤0.125 μg/mL to 64 μg/mL, with an MIC₅₀ of 0.5 μg/mL and an MIC₉₀ of 4 μg/mL. A significant increase in the MICs (fourfold or greater) of fluconazole for sequential C. albicans isolates was found for 66.6% of the patients infected with a single DNA inftype and for 50% of the patients infected with multiple DNA inftypes. Despite a limited number of patients and isolates, our data suggest that C. albicans isolates that are susceptible to fluconazole at MICs of ≥8 μg/mL in vitro will be less susceptible in vivo to standard doses (100–200 mg/d) of this drug.