Blue and red light photoemitters as approach to inhibit Staphylococcus aureus and Pseudomonas aeruginosa growth

Abstract

The ability of pathogenic bacteria acquire resistance to the existing antibiotics has long been considered a dangerous health risk threat. Currently, the use of visible light has been considered a new approach to treat bacterial infections as an alternative to antibiotics. Herein, we investigated the antimicrobial effect of two range of visible light, blue and red, on Staphylococcus aureus and Pseudomonas aeruginosa, two pathogenic bacterial commonly found in healthcare settings-acquired infections and responsible for high rate of morbidity and mortality. Bacterial cultures were exposed to blue or red light (470 nm and 660 nm) provided by light-emitting diodes - LED. The fluencies and irradiance used for blue and red light were 284.90 J/cm2, 13.19 mW/cm2 and 603.44 J/cm2, 27.93 mW/cm2 respectively. Different experimental approaches were used to determine the optimal conditions of light application. Only exposure to blue light for 6 hours was able to inhibit about 75% in vitro growth of both bacterial species after 24 hours. The surviving exposed bacteria formed colonies significantly smaller than controls, however, these bacteria were able to resume growth after 48 hours. Blue light was able to inhibit bacterial growth upon inoculation in both saline solution and BHI culture medium. We can conclude that blue light, but not red light, is capable of temporarily retarding the growth of gram negative and gram positive bacteria.

Learning from Nature: Fighting Pathogenic Escherichia coli Bacteria Using Nanoplasmonic Metasurfaces

“…[47] At proper power and wavelength, exposure to blue LED light results in the generation of toxic reactive oxygen species (ROS) that can damage components of bacteria, including the cell wall, and even the nucleus; [25] whereas red LED light has been found to have bactericidal effects mostly on gram-negative bacteria such as E. coli through thermal mechanisms, which is less effective compared to ROS. [48,49] For instance, Galo et al [48] showed that exposure of pathogenic Staphylococcus aureus and Pseudomonas aeruginosa to blue light for 6 h inhibited their growth up to 75% after 24 h while red light was ineffective. Interestingly, in terms of the emitted SPR-enhanced wavelengths at the interface, it can be similarly observed that blue SPR light at 475 nm reduced the viable E. coli population more than the red SPR light at 630 nm (Table 1).…”

“…[ 48,49 ] For instance, Galo et al. [ 48 ] showed that exposure of pathogenic Staphylococcus aureus and Pseudomonas aeruginosa to blue light for 6 h inhibited their growth up to 75% after 24 h while red light was ineffective. Interestingly, in terms of the emitted SPR‐enhanced wavelengths at the interface, it can be similarly observed that blue SPR light at 475 nm reduced the viable E. coli population more than the red SPR light at 630 nm (Table 1).…”

The effect of indoor daylight spectrum and intensity on viability of indoor pathogens on different surface materials

“…However, it should keep in mind that blue light may not be the only factor that leads to these results, as several studies have shown that other visible light spectrum outside the 400-500 nm range can also affect bacterial 36,57,58 and fungal 41,42,49 growth. Therefore, we cannot conclusively state which range within the daylight spectrum is sorely responsible for the change in the viability we observed, albeit extensive literatures have showed that visible light at 415 nm is most effective at inactivating bacteria and fungi.…”

Blue-Light-Activated Water-Soluble Sn(IV)-Porphyrins for Antibacterial Photodynamic Therapy (aPDT) against Drug-Resistant Bacterial Pathogens

“…aureus (MRSA), which is challenging to eliminate. aPDT is an alternate mode of treatment for bacterial infections. − aPDT offers several advantages over traditional antimicrobial therapies, including broad-spectrum antimicrobial activity, reduced resistance formation, and effectiveness against biofilms and drug-resistant bacteria. , Blue light (400–450 nm) activated photosensitizers are more effective against cutaneous bacterial infections than other wavelength regions of the visible spectrum. − There is less tissue penetration compared to longer wavelength light, and this prevents deeper tissue damage. , …”