Antimicrobial photodynamic therapy against Escherichia coli by exploiting endogenously produced Protoporphyrin IX- In...

Area of Science:

• Photomedicine
• Antimicrobial Therapies
• Bacteriology

Background:

• Antimicrobial drug resistance necessitates novel antibacterial strategies.
• Light-based therapies, particularly photodynamic inactivation, offer an alternative.
• Protoporphyrin IX (PpIX) is an endogenous photosensitizer in bacteria.

Purpose of the Study:

• To investigate the inactivation of Escherichia coli (E. coli) using light excitation of its Protoporphyrin IX (PpIX).
• To compare the efficacy of Light Emitting Diodes (LEDs) and laser diodes with different emission bands.
• To explore the potential of fluorescence spectroscopy as a tool for monitoring bacterial inactivation.

Main Methods:

• E. coli suspensions were exposed to LEDs (418, 522, 630 nm) and laser diodes (405, 635 nm).
• Bacterial inactivation rates were assessed using the plate count method.
• Fluorescence spectroscopy was employed to study PpIX excitation and correlate with inactivation.

Main Results:

• LEDs demonstrated a more pronounced antimicrobial photodynamic effect than laser diodes.
• The LED at 522 nm showed particular efficacy due to overlapping multiple PpIX absorption bands (505, 542, 580 nm).
• Fluorescence spectroscopy results strongly correlated with the gold standard plate count method.

Conclusions:

• Broad-band LEDs overlapping PpIX absorption bands are effective for E. coli inactivation.
• Fluorescence spectroscopy is a viable tool for monitoring photodynamic inactivation.
• This approach holds potential for in vivo disinfection of antibiotic-resistant microbes in wounds and lesions.