A longitudinal study of the change in resistance patterns and genetic relationship of oral Candida albicans from HIV-infected patients.

Candida albicans is an important opportunistic pathogen in the oral cavity of HIV-infected patients. C. albicans was isolated repeatedly over a period of 30 months from the mouth-swills of five males with category IV HIV infection who suffered from recurrent pseudomembranous oral candidosis and were being treated with fluconazole. C. albicans was identified by the germ tube test, carbon assimilation by the API 20C test (bioMerieux sa, Marcy, l'Etoile, France) and morphology on cornmeal Tween 20 agar. Sensitivity testing was performed with a disk diffusion method using neosensitabs (Rosco Diagnostica, Taasrup, Denmark) and the broth microdilution assay using RPMI 1640 medium. Isolates from the five patients taken between 14 and 30 months apart (mean = 23 months) showed the development of resistance to several antifungal agents, notably fluconazole, miconazole and itraconazole by the disc diffusion method and markedly higher minimum inhibitory concentrations (MICs) for fluconazole by the broth microdilution assay. Genetic relatedness of the C. albicans strains was assessed using the mixed-linker polymerase chain reaction method. Four patients had isolates which were genetically identical, while one patient had isolates of varying genetic type. This study has shown that in HIV-infected patients with recurrent oral pseudomembraneous candidosis, the development of drug resistance to antifungal agents may either be due to increased resistance of a single strain or replacement with a more resistant strain.