Dynamics of mixed candida species biofilms in response to antifungal treatment

描述（由申请人提供）：念珠菌具有40-50%的高死亡率，是美国医院获得性血液感染的第四大原因。这些真菌病原体通常是在哺乳动物的粘膜壁龛中发现的共生体，尤其是口腔。在免疫功能低下的患者中，念珠菌过度生长导致生物膜的形成，这在感染的发展中起着重要作用。生物膜是附着在表面并被包裹在细胞外基质中的复杂微生物群落。许多研究表明，生物膜通常比单个浮游细胞对抗菌剂更有抵抗力。这些生物膜与

DESCRIPTION (provided by applicant): With a high attributable mortality rate of 40-50%, Candida species represent the fourth leading cause of hospital-acquired bloodstream infections in the United States. These fungal pathogens are normally found as commensals in mammalian mucosal niches, especially the oral cavity. In immunocompromised patients, Candida overgrowth leads to the formation of biofilms, which play an important role in the development of infection. Biofilms are complex microbial communities that adhere to a surface and are enclosed within an extracellular matrix. Many studies have shown that biofilms are generally more resistant to antimicrobial agents than single, planktonic cells. These biofilms are associated with the opportunistic yeast infection, oral candidiasis (oral thrush), found in newborns and many patients with AIDS, diabetes and cancer. Even though C. albicans is the predominant organism found in oral thrush, there is an increasing incidence of oral thrush isolates consisting of non-albicans Candida species (especially C. glabrata, C. dubliniensis and C. tropicalis). This finding is clinically relevant since conventional doses of antifungals are sometimes ineffective at clearing these oral infections. While single-species Candida biofilms have been well-studied, considerably less is known about the composition and interaction of Candida species in mixed biofilms in response to antifungal treatment. I have recently developed a highly accurate quantitative-PCR-based approach to determine the precise species composition of mixed Candida biofilms. Preliminary data shows that the proportion of C. glabrata in the mixed biofilm increases significantly upon treatment with fluconazole. My preliminary data also indicates that the metabolic activity of biofilms is altered when these four Candida species are mixed under different nutritional environments, suggesting that biofilm composition and dynamics have changed as well. Based on this data, my hypothesis is that the shift in mixed Candida species biofilm composition and spatial architecture following antifungal treatment favors non-albicans Candida species that are intrinsically resistant or rapidly develop drug resistance. In order to test this hypothesis, I will perform experiments to address the following specific aims: (1) To determine the precise composition of mixed Candida species biofilms generated from susceptible and drug-resistant strains in the presence vs. absence of antifungal treatment and (2) To determine the spatial architecture of Candida species in mixed biofilms generated in the presence and absence of antifungal treatment. Collectively, these innovative studies will have significant impact since they will provide new information about how mixed Candida species biofilms are associated with antifungal resistance. These studies will also test the efficacy of my quantitative-PCR assay to serve as a diagnostic tool for rapid composition determination of mixed Candida biofilms (i.e. oral thrush). Since mixed Candida species biofilms are encountered more frequently, these studies will pave the way for the development of more effective antifungals to improve patient outcomes. Moreover, successful completion of this project will provide exceptional training, advance my career development and prepare me to become a pediatric dental clinician scientist.