Development of resistance in candida isolates from patients receiving prolonged antifungal therapy

The impact of prolonged antifungal therapy on the development of resistance was examined in 61 patients with oropharyngeal thrush. Fifty-nine patients had symptomatic human immunodeficiency virus infection, one had lung cancer, and one had metastatic prostate cancer. Cultures of pharyngeal samples from all patients were positive for yeasts and included 57 (93.4%) Candida albicans, 3 (4.9%) Candida glabrata, and 1 (1.6%) Candida krusii. Of 61 patients, 32 (52.5%) were receiving or had recently received antifungal therapy. Clotrimazole was the most commonly prescribed azole, followed by ketoconazole and fluconazole. Two patients had received amphotericin B therapy and one had received flucytosine. The duration of therapy with clotrimazole, ketoconazole, and fluconazole ranged from 3 to 240, 14 to 44, and 7 to 138 days, respectively. There was no overall difference in the susceptibilities of the clinical isolates from treated and untreated patients to amphotericin B, nystatin, flucytosine, clotrimazole, ketoconazole, and fluconazole. A.C. albicans isolate from one patient who had clinically failed on ketoconazole, fluconazole, and amphotericin B was resistant to these drugs. The lack of difference in the susceptibility pattern indicates that clinically significant emergence of resistance does not occur in those patients who receive prolonged antifungal therapy.