Bactericidal Effect of 405-nm LED Light against <i>Aggregatibacter Actinomycetemcomitans</i> Is Due Primarily to Disruption of Respiratory Chain Terminal Members Cytochrome <i>bd</i> Oxidase and Quinol Peroxidase

Irradiation with 405-nm visible violet LED light without additional photosensitizers decreased the viability of aggressive periodontopathic bacterium Aggregatibacter actinomycetemcomitans. The number CFU/mL linearly on a logarithm chart versus irradiation time, 1-log reduction time 1.32 min. antimicrobial photodynamic effect involved inhibition activity membrane-bound cytochrome bd, terminal quinone: oxygen oxidoreductase, and quinol peroxidase, quinone:H2O2 oxidoreductase. reduced minus oxidized difference spectrum showed that 640-nm peak (α-peak heme d) completely disappeared, height 556-nm hemes b c) Soret band (425 nm; γ-peak b, c, was to approximately half heights non-irradiated controls. Survival bacteria-injected silkworm larvae also examined. Fifth-instar were almost killed by 40 h after bacterial injection, but all irradiated (20 mW/cm2 for 5 min, energy density: 6 J/cm2) survived, similar controls not injected bacteria, indicating bacteria. bactericidal blue-light A. actinomycetemcomitans is primarily due disruption bd oxidase peroxidase respiratory chain.