Avaliação do efeito antibacteriano da terapia fotodinâmica a laser: estudo in vitro

Abstract

The increased resistance of bacteria to antibiotic drugs creats the need to develop new bacteriostatics ways and bactericidals to cooperate with the treatment of infected individuals. Among those tools are the complementary and alternative therapies involving laser therapy and photodynamic therapy. Lasers are being used isolated or associated with photosensitizing substances to work as helpers in the inactivation of bacterias, fungis and viruses. Photodynamic therapy (PDT) based on the activation of photosensitizers for visible light in low doses, with appropriate wavelength, has become an alternative to conventional treatments in the fight against oral micro-organisms, leading to death the organism by disorders in cell wall and DNA. IN VITRO study two therapies were used, Photodynamic therapy (PDT) and Low-Level Laser (LBP). For PDT we used the dye (methylene blue) to the bacteria in various concentrations, using the disk diffusion technique stimulated by laser light, wavelength 660nm, red light, InGaAlP active medium (Aluminum Indium Gallium Phosphorus). For use in the LBP isolated in micro-organisms several dosages were used with two parameters: medium active InGaAlP (Aluminum Indium Gallium Phosphorus), wavelength 660 nm, red laser and continuous emission and the active medium AsGaAl (Gallium Arsenide and Aluminum), 808 nm infrared laser and continuous emission. The bacteria used in this experiment were the standard strains American Type Culture Coletion - ATCC: Staphylococcus aureus ATCC 25922, Escherichia coli ATCC 25923 and Pseudomonas aeruginosa ATCC 27853 covering the spectrum Gram-negative bacteria, Gram-positive, aerobic and facultative anaerobic. The antibacterial effect IN VITRO of PDT in different bacteria was quantified in millimeters by observing the diameter of inhibition halos measured with the aid of a halometer. Were considered present antibacterial activities of therapy with diameter of inhibition halos greater than or equal to 8mm. Observed antibacterial effects of PDT for Staphylococcus aureus and Escherichia coli with the presence of inhibition halos with an average of 12mm, as well as for the individual use of methylene blue dye. For Pseudomonas aeruginosa was not observed anyantibacterial effect as well as for the individual use of low power laser.