Antimicrobial Blue Light versus Pathogenic Bacteria: Mechanism, Application in the Food Industry, Hurdle Technologies and Potential Resistance

Abstract

Blue light primarily exhibits antimicrobial activity through the activation of endogenous photosensitizers, which leads to the formation of reactive oxygen species that attack components of bacterial cells. Current data show that blue light is innocuous on the skin, but may inflict photo-damage to the eyes. Laboratory measurements indicate that antimicrobial blue light has minimal effects on the sensorial and nutritional properties of foods, although future research using human panels is required to ascertain these findings. Food properties also affect the efficacy of antimicrobial blue light, with attenuation or enhancement of the bactericidal activity observed in the presence of absorptive materials (for example, proteins on meats) or photosensitizers (for example, riboflavin in milk), respectively. Blue light can also be coupled with other treatments, such as polyphenols, essential oils and organic acids. While complete resistance to blue light has not been reported, isolated evidence suggests that bacterial tolerance to blue light may occur over time, especially through gene mutations, although at a slower rate than antibiotic resistance. Future studies can aim at characterizing the amount and type of intracellular photosensitizers across bacterial species and at assessing the oxygen-independent mechanism of blue light—for example, the inactivation of spoilage bacteria in vacuum-packed meats.

A New Insight into the Bactericidal Mechanism of 405 nm Blue Light-Emitting-Diode against Dairy Sourced Cronobacter sakazakii

“…The XTT activity of strain ES191 and AGRFS2961 showed that the whole population could sustain comparable metabolic rates as the control cells during the light treatment ( p > 0.05) ( Figure 1 e,f), suggesting that the light treated populations were still metabolically active ( p < 0.05). The DCFH–DA assay demonstrated that ROS production increased after 1 h of light treatment (where the cell loss became significant) ( Figure 1 and Figure 3 ), supporting the finding that light induced ROS against many different bacteria was time-dependent [ 9 , 10 ]. After 2 h, blue-LED treated samples had a reduced number of viable cells, which led to the decrease of overall ROS levels in the whole population.…”

“…However, it is still a UV-containing application. Visible light (especially blue light wavelengths from 405 to 465 nm) has been shown to have antimicrobial properties and inactivates microbes via photodynamic inactivation, where cellular molecules known as photosensitizers produce reactive oxygen species which react with cellular constituents such as lipids, proteins, and DNA to bring about a cytotoxic effect [ 9 ]. Our previous study showed that blue-LED at 405 nm caused a significant reduction (to extinction) in the levels of Escherichia coli (Shiga-toxin producing E. coli ) in vitro [ 10 ].…”

Preliminary Study on Light-Activated Antimicrobial Agents as Photocatalytic Method for Protection of Surfaces with Increased Risk of Infections

“…Guffey and Wilborn (2006) [62] studied the effect of radiation with a wavelength of 405 nm and 470 nm on the species Staphylococcus aureus, Pseudomonas aeruginosa, and Propionibacterium acnes; they noted that both types of lighting showed bactericidal effect on P. aeruginosa and S. aureus, but not on Propionibacterium acnes. Different scientists studied the effect of blue light (470 nm) on several strains of methicillin-resistant Staphylococcus aureus and the results showed that the number of colony-forming units (CFUs) of the samples exposed to light radiation of 470 nm was smaller than in the case of non-irradiated ones [63,64]. Maclean et al (2009) [52] studied the effect of light with a wavelength of 405 nm on several microbial strains responsible for nosocomial infections and observed that both Gram-positive and Gram-negative strains were inactivated after exposure.…”

Curcumin-Based Photosensitization, a Green Treatment in Inactivating Aspergillus flavus Spores in Peanuts

“…Photosensitization treatment can be used as an alternative to curb fungal growth on peanuts. The treatment combines a photosensitizer and light at the appropriate wavelength, in the presence of oxygen, to produce a cytotoxic effect towards microorganisms [15,16]. The increasing popularity of the photosensitization treatment is due to its cytotoxic effect towards a wide range of microorganisms, including Gram-negative and Gram-positive bacteria, fungi, parasites and viruses, as well as ensuring the non-emergence of resistant strains [17].…”