Effect of antimicrobial photodynamic therapy with Radachlorin and a 660 nm diode laser on Pseudomonas aeruginosa: An in vitro study

Background: Pseudomonas aeruginosa is one of the most life-threatening pathogens in nosocomial environments. This study aimed to explore whether photodynamic therapy using a 660 nm diode laser and Radachlorin is an effective in vitro inhibitor of P. aeruginosa and determine what energy density and rate of delivery are the most impactful. Methods: Suspensions ofP. aeruginosa were obtained, inoculated in petri dishes with Radachlorin, and incubated for 30 min. Then, the laser light of a 660 nm diode laser was irradiated at varying energy densities and rates of delivery. Cell viability was evaluated after culturing. Results: The combination of Radachlorin and the laser was more effective than Radachlorin or the laser alone (P < 0.05) in reducingP. aeruginosa and showed a killing rate of 95.8 % at an energy density of 5 J/cm(2). In addition, the low rate of photodynamic therapy delivery group was more effective in inhibiting P. aeruginosa compared to the high rate of photodynamic therapy delivery group (P < 0.05). Conclusions: Within the limitations of thisin vitro study, we found that photodynamic therapy using a 660 nm diode laser and Radachlorin was effective for the inhibition of P. aeruginosa. In addition, energy density and rate of delivery are important factors to consider when using a 660 nm diode laser and Radachlorin to inhibit the growth of this organism.