Femtosecond laser irradiation has an anti-virulence effect by reducing the adhesion and invasion of MRSA bacteria to human cells: an in vitro study

Purpose: Multidrug-resistant bacterial infections are a substantial global health challenge. Targeting bacterial virulence factors that control the progression, severity, and pathogenicity of bacterial infections could prevent and combat infection by intractable, potentially life-threatening pathogens such as methicillin-resistant Staphylococcus aureus (MRSA). Laser-based antibacterial photodynamic therapy (aPDT) has emerged as a promising alternative for infection management. Methods: This study assessed the attenuation of adhesion and invasion of MRSA bacteria in two human epithelial cell lines, melanoma cells (A375) and breast ductal carcinoma (T47D), after exposure to different sublethal femtosecond laser doses. The INSPIRE HF100 laser system (Spectra Physics), pumped by a mode-locked femtosecond Ti: sapphire laser MAI TAI HP (Spectra Physics), was used to provide the femtosecond laser pulses at a wavelength of 400 nm for different durations; 15, 30, and 45 min., as well as different average powers; 50, 100, and 150 mW. Results: Our results showed that, an average power of 50 mW for 15 min. significantly reduced MRSA adhesion (by ~ 84–96%) and invasion (by ~ 84–98%), even though exposure durations of 30 and 45-min. resulted in reduced viability (p < 0.0001 by ANOVA and Tukey test). Conclusion: All proposed femtosecond laser doses effectively impaired MRSA’s ability to adhere to and invade epithelial cells.