Beyond traditional therapies: a narrative overview of antimicrobial photodynamic therapy in combating bacterial and viral infections.

The increasing prevalence of multidrug-resistant bacteria and emerging viruses urgently requires new antimicrobial approaches. Photodynamic therapy (PDT) combining light, photosensitizers, and molecular oxygen generates reactive oxygen species (ROS) that disrupt microbial cells, including in biofilms. In this review, we present recent clinical and preclinical evidence for PDT's effectiveness against both Gram-positive and Gram-negative bacteria, oral/dental pathogens, and viral structures. We highlight applications such as periodontal therapy, root canal disinfection, denture stomatitis, and skin/surface fungal infections. Findings show that PDT produces large log reductions in bacterial counts, dismantles biofilm architecture, and yields improvements in clinical measures (e.g., reduced probing depth and bleeding). Although safety appears favorable, the main limitations are inconsistent photosensitizer types, variable light doses and treatment durations, and a shortage of large-scale clinical trials. PDT holds strong potential not only as an adjunct but possibly as a primary therapy against infections by multidrug-resistant pathogens. Future work should focus on standardizing protocols, optimizing delivery systems (e.g., via nanotechnology or nano-drug delivery systems), and conducting larger, rigorous clinical trials to establish PDT's routine use in infectious disease management.