Biology and Drug Resistance of Candida Biofilms

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DESCRIPTION (provided by the applicant): Candida-associated denture stomatitis (chronic atrophic candidiasis) is the most prevalent superficial oral infection and the most common form of Candida-associated disease. The etiology of denture stomatitis involves dental plaque. Dental plaque consists of a complex biofilm of bacteria and yeasts, predominantly Candida albicans. C. albicans biofilms have received much less attention than bacterial biofilms, and our present knowledge of their biology and drug resistance is at a rudimentary stage. Frequent denture stomatitis treatment failures combined with a steadily increasing population of elderly people, many of whom will be endentulous, make this area of study particularly important. The long-range goal of our work is to understand the biology and drug resistance of C. albicans biofilms. Our preliminary work in this new area resulted in the successful development of a reproducible model of C. albicans-associated biofilms (Publication #1). Since the last submission, we used this model to: 1) define the three stages of C. albicans associated biofilm development, 2) demonstrate that C. albicans biofilm is a highly heterogeneous structure, 3) show that the antifungal resistance of C. albicans biofilm increases in conjunction with biofilm development, 4) show that C. albicans has greater ability than the less pathogenic C. parapsilosis and Saccharomyces cerevisiae to form denture biofilm, and 5) show that C. albicans genes are differentially expressed under biofilm and planktonic conditions. Additionally, we initiated efforts to construct a C. albicans DNA array, and developed a bioprosthetic associated candidal biofilm model. Importantly, our studies showed that biofilm grown in our in vitro model has similar morphology as that growing in vivo on a catheter obtained from a patient with catheter-associated infection. Specific aims of the current proposal are: Specific Aim 1: Use our established biofilm model to determine the antifungal susceptibility profiles of C. albicans isolates obtained from denture stomatitis patients, and to study the effect of antifungal agents on the growth kinetics of C. albicans bioflims. Specific Aim 2: Investigate the mechanism(s) responsible for increased antifungal resistance of biofilm-associated C. albicans. Specific Aim 3: Identify genes that are involved in the formation and contribute to the development of antifungal resistance of C. albicans biofilms. By studying biofilm model systems and applying this knowledge to the patient population, we will gain a wealth of data about the biology and drug resistance of C. albicans in biofilms.