Antimicrobial blue light inactivation of microbial pathogens: State of the art

Although microbiologists have been ringing the alarm bell for years, the threat of antibiotic resistance has reached new prominence in the popular press that the issue should be added to the list of global emergencies. It is now indisputable that antibiotic resistance is life-threatening in the same sense as cancer, both in the number of cases and the likely outcome. New therapeutic approaches are urgently needed to combat antibiotic-resistant microbial pathogens. In response, the United States Government has recently accelerated efforts to advance innovative research on antibiotic resistance, with special attention to the treatment of multidrug-resistant Gram-negative bacteria, which are of particular concern because of their diverse and rapidly evolving mechanisms of resistance (White House. National Action Plan for Combating Antibiotic-Resistant Bacteria
2020-2025).

Antimicrobial blue light (aBL) in the spectrum of 400-470 nm, as an innovative non-antibiotic approach, has demonstrated its intrinsic antimicrobial activity resulting from the photoexcitation of naturally occurring endogenous photosensitizing chromophores in microbial pathogens and the subsequent production of cytotoxic reactive oxygen species. In this tutorial, I will present an overview of our laboratory's recent efforts in
exploring the utility of aBL for treating antibiotic-resistant localized infections. Topics will include the susceptibilities of Gram-negative bacteria and other pathogens to killing by aBL, mechanism of action of aBL, synergism of aBL with traditional antibiotics for enhanced antimicrobial activity, potential side effects of aBL on the host cells and tissues, the development of novel optical devices for infection treatment, preclinical studies of aBL therapy for localized infections (e.g., skin wound infections, keratitis, implant-related infections, etc ), and future directions in the field of aBL therapy.