The Dual Synergy of Photodynamic and Sonodynamic Therapy in the Eradication of Methicillin-Resistant Staphylococcus aureus

Recently, the combined application of synergistic therapies for photodynamic antimicrobial chemotherapy has become important to obtain more efficient results. The synergism between two sensitizers, rose bengal (RB) and chlorin e6 (Ce6), excited by two different methods, was evaluated as a novel approach to both photodynamic and sonodynamic therapy against methicillin-resistant Staphylococcus aureus. The sonostability and singlet oxygen generation (with 1,3-diphenylisobenzofuran for RB and tetrathiafulvalene for Ce6) were measured under sonication (1 MHz, 3 W) using a spectrophotometer. RB and Ce6 remained stable during sonication. RB was a more efficient sonosensitizer than Ce6. The dual synergism between RB and Ce6 was noticed, achieving a >3 log reduction for molar ratios RB:Ce6 of 1:1 and 1:3, while, alone, the sensitizers excited with ultrasound and light, respectively, achieved only ca. a 1 log reduction.