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Photodynamic inactivation of Staphylococcus aureus and Escherichia coli biofilms by malachite green and phenothiazine dyes: An in vitro study
Scritto da Archives of Oral Biology   
Chirurgia oraleAbstract: Objectives: The organization of biofilms in the oral cavity gives them added resistance to antimicrobial agents. The action of phenothiazinic photosensitizers on oral biofilms has already been reported. However, the action of the malachite green photosensitizer upon biofilm-organized microorganisms has not been described. The objective of the present work was to compare the action of malachite green with the phenothiazinic photosensitizers (methylene blue and toluidine blue) on Staphylococcus aureus and Escherichia coli biofilms.Methods: The biofilms were grown on sample pieces of acrylic resin and subjected to photodynamic therapy using a 660-nm diode laser and photosensitizer concentrations ranging from 37.5 to 3000?M. After photodynamic therapy, cells from the biofilms were dispersed in a homogenizer and cultured in Brain Heart Infusion broth for quantification of colony-forming units per experimental protocol. For each tested microorganism, two control groups were maintained: one exposed to the laser radiation without the photosensitizer (L+PS?) and other treated with the photosensitizer without exposure to the red laser light (L?PS+). The results were subjected to descriptive statistical analysis.Results: The best results for S. aureus and E. coli biofilms were obtained with photosensitizer concentrations of approximately 300?M methylene blue, with microbial reductions of 0.8?1.0log10; 150?M toluidine blue, with microbial reductions of 0.9?1.0log10; and 3000?M malachite green, with microbial reductions of 1.6?4.0log10.Conclusion: Greater microbial reduction was achieved with the malachite green photosensitizer when used at higher concentrations than those employed for the phenothiazinic dyes.
Fonte: Archives of Oral Biology

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