Expressão gênica de Streptococcus mutans em biofilmes produzidos in vitro submetidos à terapia fotodinâmica antimicrobiana

Abstract

The early stages of the formation of caries lesions in humans are directly related to the presence of Streptococcus mutans in biofilm. The treatment of diseases caused by oral biofilms basically involves mechanical removal and use of antibiotics and antiseptic agents which may lead to strains resistant to traditional antimicrobials. Antimicrobial Photodynamic Therapy (PACT) presents itself as an alternative option to conventional treatment, promoting bacterial killing by photosensitizing of microbial components. The objective of this study was to evaluate the antimicrobial potential of PACT and its ability to alter the pattern of gene expression of S. mutans in oral biofilms produced in vitro using both a LED light (LED) associated with the photosensitizer ortho-toluidine blue ( TBO). To this end, S. mutans UA159 biofilms were formed on hydroxyapatite discs using a model of bathing culture and were subjected to PACT after 5 days. The collected material has gone through sonication for dispersion and dilution of cells in decimal series. After that, material was plated in rich medium and incubated under optimum growth conditions. Additionally, expression of virulence gtfB, and gtfC gbpB genes of S. mutans were evaluated after extraction of total RNA, cDNA synthesis and realization of the technique of polymerase chain reaction in real time using specific primers. The 16S ribosomal gene was used as the reference gene. Significant reductions (p <0.05) were observed in the viability of colonies of S. mutans when exposed to TBO and LED at the same time. Gene expression of gtfC in S. mutans biofilm was significantly reduced after the completion of antimicrobial photodynamic therapy, whereas expression of gtfB seems to have been less influenced by therapy. No change in the expression of gbpB a function of antimicrobial photodynamic therapy was observed. Therefore, further studies are needed to evaluate the action of antimicrobial photodynamic therapy in conditions more like those found in the clinical environment and to encourage understanding of their effects on the expression of important virulence of S. mutans genes.