A wide variety of diseases, previously unrecognized or self-limiting in healthy individuals, have become life-threatening, recurring and chronic manifestations in HIV-infected patients. Control of many of these infections is crucial not only in prolonging the lives of these individuals, but also in ensuring the quality of life during HIV-disease progression. Current treatments for AIDS-associated infections, including oral candidiasis, are becoming less effective in part because many opportunistic pathogens are developing resistance to the currently used drugs. In the treatment of recurrent candidiasis, the use of azole antifungals for prophylaxis, including fluconazole, may have contributed to the recent, dramatic increase in Candida strains that are resistant to several antifungal drugs. At this time, we know little about the extent of antifungal drug resistance in Candida albicans, its predisposing factors or the most frequent mechanisms that result in resistance. The goal of this proposal is (1) to determine the frequency and the levels of emerging antifungal resistance in HIV-infected populations from the San Francisco area and (2) to use molecular techniques to discern possible mechanisms by which antifungal resistance occurs. Together, these findings should help In the development of strategies to minimize and treat the emergence of antifungal resistance. Candida samples from a large number of HIV-infected and high risk individuals are available through the AIDS Specimen Bank at the University of California at San Francisco (UCSF) as part of two cohort groups: patients (mostly male) at the Oral AIDS Center Clinic at UCSF, and women in the Bay Area Research Consortium on Women with AIDS (BARCWA) cohort. These groups include not only homosexual and bisexual males, but a large and representative group of HIV-infected women. Candida samples will be characterized with respect to species and strain, levels of antifungal resistance and possible cofactors associated with resistance. Highly- resistant strains of Candida will be selected for molecular analyses to identify genetic alterations (amplifications, rearrangements, point mutations) in the azole target enzyme, lanosterol demethylase (and in other genes associated with drug resistance). Gene-specific alterations correlated with resistance will be tested in vitro with DNA transformations to demonstrate their effect on antifungal drug resistance. Simple tests for these mutations will then be used to screen Candida isolates from the cohorts to determine the frequency of each alteration in clinically resistant samples. The identification of the predominant mechanisms of antifungal resistance in Candida will focus research efforts on ways to avoid or overcome these genomic alterations. The results of this study will allow us to identify drug resistance early in treatment and to avoid, reduce, or eliminate Candida drug resistance during extended prophylactic treatment in the HIV-infected population.