In Vitro Evaluation of the Antibacterial Effect of Photodynamic Therapy with Methylene Blue

Maria Helena Chaves De Vasconcelos Catão,Ana Luzia Araújo Batista

doi:10.1590/pboci.2020.073

Maria Helena Chaves De Vasconcelos Catão, Ana Luzia Araújo Batista

Open Access

https://doi.org/10.1590/pboci.2020.073

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Abstract

Objective: To evaluate, in vitro , the effect of photodynamic therapy (PDT) compared to laser therapy and the use of a photosensitizer alone. Material and Methods: The following therapies were used: PDT, laser therapy and photosensitizer alone. For PDT, methylene blue (MB) at different concentrations and red laser InGaAlP 660nm were used. For the use of low-power laser (LPL) alone, red laser InGaAlP 660 nm and infrared laser AsGaAl, 830 nm, both in continuous emission were used. Standard ATCC strains of Staphylococcus aureus ( S. aureus ), Escherichia coli ( E. coli ) and Pseudomonas aeruginosa ( P. aeruginosa ) species were used. The antibacterial effect of PDT was quantified by the diameter of the inhibition halos . Results: PDT (LPL 660 nm, 320 J/cm2) with MB at concentration of 50 μ g/mL showed antibacterial efficacy only when tested against S. aureus and E. coli strains, as well as with the isolated use of MB at the same concentration. Using LPL alone, whether red or infrared, with different dosimetry, no antibacterial effect was observed. In none of the therapeutic modalities used, P. aeruginosa inactivation was observed . Conclusion: Antibacterial effects of PDT (LPL 660 nm + MB 50 μ g/mL) were observed for S. aureus and E. coli , as well as with the isolated use of MB (50 μ g/mL). For P. aeruginosa , no antibacterial effect with any of the protocols recommended in the study was observed.

Highlights

The oral cavity is colonized by approximately one thousand species of microorganisms and most are organized as biofilms [1]
Standard American Type Culture Collection (ATCC) strains of Staphylococcus aureus (S. aureus), Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa) species were used
In view of the diversity of microorganisms present in the oral cavity and the need to balance the endogenous flora to maintain the health of the individual as a whole, this study evaluated the in vitro antibacterial effect of photodynamic therapy (PDT) with methylene blue (MB) at in different concentrations on three bacterial strains P. aeruginosa, E. coli and S. aureus compared to the use of low-power laser (LPL) and MB alone

Summary

Introduction

The oral cavity is colonized by approximately one thousand species of microorganisms and most are organized as biofilms [1]. The dental biofilm is formed through an orderly and dynamic process where there is need for fixation and proliferation of bacteria on tooth surfaces, which may lead to the growth of the adhered species and appearance of additional species [2]. The accumulation of the bacterial biofilm complex results in diseases induced by the most prevalent bacteria: caries and periodontal disease. Current treatment of subjects with plaque related diseases involves mechanical removal of the biofilm and the use of antiseptics and antibiotics [3,4]. Mutations can occur with the use of a single antibiotic [5]

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Conclusion