Antimicrobial blue light: bacterial targets and mechanism of action

Author(s)

Carolina dos Anjos

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD)
• Defense date: 2021-10-01

Examining board members

Fabio Celidonio Pogliani; Milena Dropa; Alessandra Nara de Souza Rastelli; Martha Simões Ribeiro; Fernando Nogueira de Souza

• Advisor: Fabio Celidonio Pogliani; Fabio Parra Sellera

Abstract

There is growing concerned about the future of antimicrobial therapies amid the global antibiotic crisis. Fearful, international authorities warn of the urgency of developing alternative antimicrobial therapies or preserving currently available antimicrobials. In this context, antimicrobial blue light stands out as a promising therapeutic alternative due to its intrinsic antimicrobial activity, providing efficacy and safety in treating infections. However, the cellular targets are not yet well understood. Thus, this study aimed to test common hypotheses related to biological targets of bacterial death induced by exposure to antimicrobial blue light (λ = 410 nm). This study investigated three bacterial species: Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. Endogenous porphyrins were quantified, and structural damage such as DNA and bacterial membrane were evaluated. Changes in biomolecules such as proteins and lipids and the production of EROS after exposure to blue light were also measured. The results show that sublethal doses of blue light may promote damage to the bacterial membrane, suggesting that this is the primary target of antimicrobial action. DNA degradation was evidenced in S. aureus and E. coli, but no damage was observed in P. aeruginosa, suggesting particularities between different species. Evidence showed that the concentration of endogenous porphyrins might not directly reflect bacterial susceptibility to blue light. Additionally, it found oxidative damage to bacterial proteins and lipids occurs only after high radiant exposure doses. These results confirm some crucial aspects regarding the antimicrobial mechanisms of blue light and provide essential information that will empower optimizations and future combined therapies. (AU)

• FAPESP's process: 16/25095-2 - BACTERIAL PHOTOINACTIVATION OF MASTITIS PATHOGENS BY BLUE LIGHT: MECHANISMS OF ACTION AND CELL SECURITY - PRE-CLINICAL STUDY
• Grantee: Carolina dos Anjos
• Support Opportunities: Scholarships in Brazil - Doctorate