Synergistic in vitro photodynamic antimicrobial activity of methylene blue and chitosan against Helicobacter pylori 26695

Photodynamic therapy (PDT) is a method for killing cells (bacterial, fungal and cancer cells) or virus using photosensitizers (PS) and light of various wavelengths. In vitro PDT using endoscopic light against H. pylori was effective at a concentration of 0.2. mg/mL of MB. The purpose of this study was to increase the effect of photodynamic modality against H. pylori by addition of chitosan to MB. Methods: The bactericidal effect was measured by counting viable cells after PDT. The degree of damage to DNA was confirmed using alkaline gel electrophoresis. Cellular DNA damage was demonstrated by ethidium bromide monoazide-quantitative polymerase chain reaction (EMA-qPCR). Results: In the groups treated with either 0.04mg/mL MB alone or 0.02mg/mL MB with endoscopic light for 15min, viable cells were decreased approximately tenfold. The group treated with 0.04mg/mL of MB with light, showed more effective bactericidal activity than 0.02mg/mL of MB treatment. By 0.05% chitosan pre-treatment followed with 0.04mg/mL of MB and light irradiation, viable cells were decreased 10⁷-fold. The DNA damage caused by PDT as demonstrated by alkaline gel electrophoresis was greater in the MB plus chitosan-treated group than in control and MB-treated groups. Cellular DNA damage demonstrated by EMA-qPCR was also greater in the group treated with MB plus chitosan than in the MB-treated group. Conclusion: The bactericidal effects with PDT using MB were increased with the concentration of photosensitizer and chitosan treatment, peculiarly before endoscopic light irradiation.