Photoxidative effects on S. aureus after photodynamic inactivation cycles

Fighting antibiotic resistance is one of the greatest challenges of the 21st century. Photodynamic inactivation (PDI) cycles at subtherapeutic doses, in addition to eliminating both antibiotic-sensitive and -resistant bacterial cells, can enhance the action of antibiotics. In this study, curcumin at 10 µM and 450 nm irradiation with a fluence of 10 J/cm² are applied to methicillin-resistant Staphylococcus aureus (MRSA) cultures at 8-hour intervals. After each cycle, the minimum inhibitory concentration (MIC) of the antibiotic is determined. Over the course of the PDI treatments, the MIC of MRSA decreases significantly, altering its phenotypic classification from resistant to sensitive. Thus, photo-oxidative action may represent a promising strategy for combined treatment with antibiotic therapy in bacterial infections