Effect of rutin as flavonoid compound on photodynamic inactivation against P. aeruginosa and S. aureus

Abstract Antimicrobial photodynamic therapy (aPDT) has drawn increasing attention for its potential to effectively kill multidrug-resistant pathogenic bacteria and also for its low tendency to induce drug resistance. Antimicrobial photodynamic therapy (aPDT) is the application of photoactive dye followed by light irradiation that leads to the death of microbial cells mainly by reactive oxygen species (ROS) production in the presence of oxygen molecules. Methylene Blue (MB) as a photosensitizer is a hydrophobic drug molecule and prone to aggregation and dimer formation which lead to its low phototoxicity. Rutin, a flavonoid compound which is derived from plants such as wheat, apple, and tea has many properties such as antibacterial activity. In this study, we investigated the effect of rutin as a flavonoid compound on photodynamic inactivation by MB on Pseudomonas aeruginosa and Staphylococcus aureus. After performing the Minimum Inhibitory Concentration (MIC) assay (to measure minimum inhibitory concentration) and the MTT assay (to evaluate methylene blue toxicity), the effect of aPDT at 660 nm and pretreatment or post treatment with rutin on bacteria in the forms of planktonic and biofilm were investigated. The results showed that by a combination of rutin (800 μg/mL) with methylene blue (MB 8 μg/mL) as a photosensitizer and aPDT (660 nm, 5 min), there is a more reduction in the number of bacteria in the planktonic condition and bacterial biofilm production in comparison to MB alone. MB-aPDT showed no toxic effect against human dermal fibroblast with the proposed strategy which could suggest its application with rutin as a novel approach in the treatment of bacteria in wound infection.