Resumo

The Candida albicans commensal yeast can cause superficial infections, such as oral candidiasis, which begins with the adherence of yeast to buccal epithelial cells and the subsequent colonization, biofilm formation and damage to host tissues. Biofilms formed by C. albicans are composed of blastoconidia, pseudohyphae and hyphae embedded in extracellular polymeric substances that form channels and pores. This structure constitutes an important virulence factor that confers protection from the immune system and resistance to chemical and antifungal agents. Thus, this study assessed the action of photodynamic inactivation (PDI) on biofilm of C. albicans formed in vivo and adherence of the yeasts to buccal epithelial cells (BECs) in vitro. The biofilm was formed on the tongue dorsum of immunosuppressed mice (56 animals) that were subjected to PDI mediated by erythrosine (400 µM) and green light emitting diode (LED) (14.34 J.cm^-2). After treatment, the yeasts recovered from the mice were quantified (CFU/mL) and analyzed for the effects of PDI on their adherence to BECs. The tongues were removed for macroscopic and microscopic analysis. The data were analyzed by ANOVA, Tukey’s test, Kruskal-Wallis test and Student’s t test. PDI reduced significantly the amount of yeasts present in the biofilm by 0.73 log₁₀ and reduced C. albicans adherence to BECs by 35% without damaging adjacent tissues, but there was not significant reduction of macroscopic and microscopic lesions among the groups. Scanning electron microscopy (SEM) showed numerous hyphae and alterations on the tongue. Blastoconidia budding and germ tubes were seen adhered on BECs analyzed by light microscopy and SEM. PDI presented antifungal effects against C. albicans biofilm formed in vivo and reduced the ability of C. albicans to adhere to BECs in vitro. We acknowledge the FAPESP for financial support (Grants 2009/52048-1 and 2010/18753-7) and scholarships (Processes 2009/12005-1, 2010/01988-1 and 2010/00879-4).