Curcumin-mediated photodynamic inactivation of Escherichia coli , Pseudomonas fluorescens , and Candida auris

Photodynamic therapy (PDT) is an emerging antimicrobial strategy that uses light to activate photosensitizers, generating reactive oxygen species (ROS) that induce microbial cell death. This study investigates the antimicrobial efficacy of curcumin-mediated PDT against the microbial pathogens Escherichia coli, Pseudomonas fluorescens , and Candida auris . The minimum inhibitory concentration (MIC) for each microorganism is determined at different light fluence rates within a clinically relevant range. Our results demonstrate that curcumin-mediated PDT effectively inactivates E. coli and C. auris , while exhibiting only partial inhibition against P. fluorescens at curcumin concentrations up to 60 µM. Notably, within the tested fluence rate range, the total light dose appears to be a more critical determinant of antimicrobial efficacy than the specific fluence rate itself. The observed variations in microbial susceptibility highlight the importance of species-specific factors, such as cell wall/membrane structure. These findings provide guidelines for the application of curcumin-mediated PDT in combatting antimicrobial resistance.