Porphyrins and flavins as endogenous acceptors of optical radiation of blue spectral region determining photoinactivation of microbial cells

Antimicrobial Blue Light Inactivation of Neisseria gonorrhoeae: Roles of Wavelength, Endogenous Photosensitizer, Oxygen, and Reactive Oxygen Species

“…In this study, the culture conditions of N. gonorrhoeae were kept consistent before testing the inactivation effects of aBL and the quantity of endogenous photosensitizers. The presence of endogenous photosensitizing chromophores in some aBL‐sensitive microbial strains were verified in several recent studies . However, quantitative analysis were only carried in some of these studies.…”

Visible Light as an Antimicrobial Strategy for Inactivation of Pseudomonas fluorescens and Staphylococcus epidermidis Biofilms

“…Inactivation was claimed by Halstead et al as well, who investigated 400 nm light against 34 isolates and found violet light effective against P. aeruginosa and S. aureus [53]. Based on these findings and the literature, there is no doubt about the antibacterial activity of the violet light [32,40,41,43,49,51,54,56,[63][64][65][66][67]. However, the evaluation of its effectiveness and a direct comparison of the results, obtained by different studies, are more complicated.…”

“…The findings of Section 2.5 also demonstrated that inactivation (light-killed population) of P. fluorescens biofilms was stronger than S. epidermidis biofilms when the total dose irradiating the samples was lower (2.5% and 25% I max , Figure 3 in Section 2.5). It can be conceivably hypothesized that the difference between P. fluorescens and S. epidermidis inactivation may be due to the presence of different endogenous PSs within each bacterial species having different absorption spectra [38][39][40][41]47]. Another reason may be the different quantity of PSs absorbing light per bacterial cell: a higher concentration leads to increased reactive oxygen species production and, therefore, a stronger killing effect under lower irradiation conditions.…”

“…In some works, blue light (420-470 nm) has been tested as well, showing a strong effect against both Gram-positive (Bacillus cereus, Listeria monocytogenes and methicillin-resistant S. aureus) and Gram-negative pathogens (P. aeruginosa, Salmonella Typhimurium and E. coli) in their planktonic form [39][40][41]49,50,54,56,[65][66][67][68]. However, Abana et al claimed that the effect of 455 nm is not completely bactericidal on E. coli but depends on the microorganism (pathogenic or non-pathogenic) and growth phase.…”

“…Then, based on the literature that focused on the investigation of the endogenous PSs responsible for the photoinactivation and considering the absorption spectra of the porphyrins and flavins, it is possible to claim that the wavelengths with the strongest antibacterial effect are the ones belonging to the main absorption peak: violet-blue range [38][39][40][41]47]. Although the other wavelengths of the visible spectra followed in correspondence with the secondary absorption peaks of the same chromophores, they were harmless [38][39][40][41]47].…”