Heterogeneity in antifungal susceptibility of clones of Candida albicans isolated on single and sequential visits from a HIV-infected southern Chinese cohort

The increased frequency and severity of candidal infections in human immuno deficiency virus (HIV)-infected individuals has prompted the wide use of an tifungals, such as amphotericin B, ketoconazole, and fluconazole, resulting in the emergence of drug-resistant strains of Candida albicans. To study t his phenomenon in an ethnic Chinese cohort, we isolated multiple colonies o f Candida from the oral cavities of 16 HIV-infected patients on single and subsequent sequential visits over a period of 12 months. Ten of the 16 pati ents had sporadic episodes of oropharyngeal candidiasis (Group A), while th e remainder were asymptomatic with respect to this condition (Group B). Ora l rinses were collected and immediately processed in the laboratory for the isolation of C. albicans in a standard manner. A total of 433 C. albicans isolates were tested for their susceptibility to amphotericin B, ketoconazo le and fluconazole by an agar diffusion method using the commercially avail able E-test. All tested isolates demonstrated variable susceptibility to am photericin B, ketoconazole and fluconazole. The minimum inhibitory concentr ation (MLC) of the isolates for amphotericin B, ketoconazole and fluconazol e ranged from <0.002-1.5 <mu>g/ml, <0.002-4.0 <mu>g/ml and <0.016-32 <mu>g/ ml, respectively. Sequential isolates of a few patients demonstrated variab le susceptibility to all the antifungals, and no discernible MIC pattern em erged either in group A or B over time. Interestingly, significant variatio n in antifungal susceptibility was also noted in isolates obtained from the same patient on a single visit. Sequential yeast isolates in 9 of 16 patie nts (56%) demonstrated significant differences in MIC within and between vi sits for both amphotericin B and ketoconazole, while a lower percentage - 4 4% (7/16) - exhibited this trait for fluconazole. Our study demonstrates th e diversity in antifungal susceptibility in either commensal or "infective" oral strains of C. albicans in HIV disease, and shows the need for vigilan ce for the emergence of resistant strains, and for frequent antifungal susc eptibility studies.