Blue Light Improves Antimicrobial Efficiency of Silver Sulfadiazine Via Catalase Inactivation.

Background: Blue light exhibits the ability to deactivate catalase present in pathogens, significantly improving the antimicrobial performance of compounds such as hydrogen peroxide (H₂O₂). However, H₂O₂ is not used within clinical settings due to its short half-life, limiting its potential applications. In this study, we explore the usage of Food and Drug Administration-approved and clinically used silver sulfadiazine (SSD) as a potential alternative to H₂O₂, acting as a reactive oxygen species (ROS)-producing agent capable of synergizing with blue light exposure. Materials and methods: For in vitro studies, bacterial strains were exposed to a continuous wave 405 nm light-emitting diode (LED) followed by treatment with SSD for varying incubation times. For in vivo studies, bacteria-infected murine abrasion wounds were treated with daily treatments of 405 nm LED light and 1% SSD cream for up to 4 days. The surviving bacterial population was quantified through agar plating and colony-forming unit quantification. Results: Through a checkerboard assay, blue light and SSD demonstrated synergistic interactions. Against both gram-negative and gram-positive pathogens, blue light significantly improved the antimicrobial response of SSD within both phosphate-buffered saline and nutrient-rich conditions. Examination into the mechanisms reveals that the neutralization of catalase significantly improves the ROS-producing capabilities of SSD at the exterior of the bacterial cell, producing greater amounts of toxic ROS capable of exerting antimicrobial activity against the pathogen. Additional experiments reveal that the incorporation of light improves the antimicrobial performance of SSD within methicillin-resistant Staphylococcus aureus (MRSA)- and Pseudomonas aeruginosa strain 1 (PAO-1)-infected murine abrasion wounds. Conclusions: As an established, clinically used antibiotic, SSD can act as a suitable alternative to H₂O₂ in synergizing with catalase-deactivating blue light, allowing for better translation of this technology to more clinical settings and further implementation of this treatment to more complex animal models.