The association of light and ultrasound for the disruption of Staphylococcus aureus biofilms

Due to the progression of antimicrobial resistance, Photodynamic (PDI) and Sonodynamic (SDI) Inactivation therapies arose as promising approaches for microbial control. Recently, the combination of both therapies, called Sonophotodynamic Inactivation (SPDI), have shown greater effects than the single treatments. This study evaluated the effectiveness of PDI, SDI and SPDI mediated by curcumin (Cur) against Staphylococcus aureus biofilm and the structural impact of these treatments on the biofilm community. For, this S. aureus biofilms received PDI, SDI and SPDI, mediated by Cur (80 mu M), LED light (450 nm), and 1 MHz ultrasound (20% of duty cycle, 1.5 W/cm(2) of intensity). The effectiveness of the treatments was measured by cell viability assay (quantification of colonies - CFU/mL), metabolic activity (XTT assay) and total biomass of the biofilms was quantified by crystal violet. Additionally, the biofilm architecture after treatments was evaluated under confocal fluorescence microscopy. SPDI was more effective than PDI and SDI. The SDI, PDI and SPDI groups demonstrated reductions of 1 +/- 1, 1 +/- 1, and 3 +/- 1 log, respectively, compared to the control group. The PDI group exhibited a metabolic activity 89 +/- 1% lower than the control, while SDI and SPDI showed 82 +/- 2% and 90 +/- 1%, respectively. All treatments reduced the total biomass of the biofilms. The PDI samples exhibited a 43 +/- 9% reduction in total biomass, the SDI group showed a 25 +/- 11% reduction, and the SPDI group demonstrated a 49 +/- 11% reduction in comparison with the control group. Finally, all treatments impacted the biofilm components and structure, reducing the cells and matrix. In conclusion, SPDI was more effective in the inactivation and had greater impact on the S. aureus biofilm.