The aims of this study will be to isolate and identify opportunistic microorganisms in lesions of denture stomatitis (DS) and verify the production of virulence factors by Candida albicans, Candida dubliniensis, Candida glabrata and Candida tropicalis; evaluate the effects of photodynamic therapy (PDT) on planktonic cultures and biofilms formed by these yeasts. In addition, the effect of PDT will be assessed on the virulence factors of these yeasts. 50 patients with DS and 50 individuals without DS will be examined. The samples from oral cavity will be collected with sterile swabs and through rinse mouth. Samples will be seeded onto selective agar and the organisms will be identified biochemically by the API® system. For C. dubliniensis, this identification will also be performed using the technique of Polymerase Chain Reaction (PCR). Isolates identified as C. albicans, C. dubliniensis, C. glabrata and C. tropicalis will be assessed for the production of the following virulence factors: secretion of the enzyme phospholipase, proteinase, chondroitinase, lipase, hemolysin; cell surface hydrophobicity; germ tube production; and biofilm formation. The assays of PDT will be performed in planktonic cultures, and in biofilms formed by the Calgary Biofilm Device (CBD), with strains of C. albicans, C. glabrata, C. tropicalis and the isolates of C. dubliniensis that have higher and lower expression of virulence factors. A green light emitting diode (532 ± 10 nm) with the output power of 80 mW will be used as a light source and erythrosine as photosensitizer. The number of colony-forming units per milliliter (CFU/mL) in Log10 will be analyzed statistically (p <0.05). Scanning electron microscopy and confocal laser scanning microscopy on discs treated with PDT and control biofilms groups will be performed. After testing of PDT in planktonic and biofilm cultures of C. albicans, C. dubliniensis, C. glabrata and C. tropicalis, the phenotypic expression of the virulence factors will be evaluated in yeast remaining again.
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