Daily Administered Dual-Light Photodynamic Therapy Provides a Sustained Antibacterial Effect on Staphylococcus aureus

Area of Science:

• Photomedicine
• Microbiology
• Biotechnology

Background:

• Excessive antibiotic use drives the urgent need for novel antimicrobial strategies.
• Staphylococcus aureus biofilms present a significant challenge due to their resistance to conventional treatments.

Purpose of the Study:

• To evaluate the efficacy of dual-light antimicrobial photodynamic therapy (aPDT) against Staphylococcus aureus biofilms.
• To investigate the impact of varying light energy ratios and indocyanine green (ICG) on aPDT effectiveness.
• To assess the sustained bactericidal effects of dual-light aPDT.

Main Methods:

• Testing single-light aPDT (810 nm) and blue light (aBL, 405 nm) versus dual-light aPDT (simultaneous 810 nm aPDT and 405 nm aBL) with ICG.
• Applying constant light energy doses (100 or 200 J/cm²).
• Exposing biofilms after one, three, or six days of incubation, with single or repeated daily light doses.

Main Results:

• Dual-light aPDT with a higher proportion of aBL (405 nm) was most effective against one-day biofilms at 100 J/cm².
• For three-day biofilms, single-dose aPDT or dual-light aPDT outperformed aBL alone.
• All dual-light treatments at 200 J/cm² demonstrated effectiveness, with repeated application enhancing the bactericidal effect.

Conclusions:

• Dual-light aPDT significantly enhances bactericidal effects against Staphylococcus aureus biofilms compared to single-light aPDT or aBL alone.
• The ratio of light components, particularly an increased proportion of aBL, is crucial for optimizing antibacterial efficacy, especially with repeated treatments.
• Dual-light aPDT offers a promising alternative for managing antibiotic-resistant bacterial infections.