Antibacterial Activity of Blue Light against Nosocomial Wound Pathogens Growing Planktonically and as Mature Biofilms

Abstract

The blue wavelengths within the visible light spectrum are intrinisically antimicrobial and can photodynamically inactivate the cells of a wide spectrum of bacteria (Gram positive and negative) and fungi. Furthermore, blue light is equally effective against both drug-sensitive and -resistant members of target species and is less detrimental to mammalian cells than is UV radiation. Blue light is currently used for treating acnes vulgaris and Helicobacter pylori infections; the utility for decontamination and treatment of wound infections is in its infancy. Furthermore, limited studies have been performed on bacterial biofilms, the key growth mode of bacteria involved in clinical infections. Here we report the findings of a multicenter in vitro study performed to assess the antimicrobial activity of 400-nm blue light against bacteria in both planktonic and biofilm growth modes. Blue light was tested against a panel of 34 bacterial isolates (clinical and type strains) comprising Acinetobacter baumannii, Enterobacter cloacae, Stenotrophomonas maltophilia, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Enterococcus faecium, Klebsiella pneumoniae, and Elizabethkingia meningoseptica. All planktonic-phase bacteria were susceptible to blue light treatment, with the majority (71%) demonstrating a ≥5-log10 decrease in viability after 15 to 30 min of exposure (54 J/cm2 to 108 J/cm2). Bacterial biofilms were also highly susceptible to blue light, with significant reduction in seeding observed for all isolates at all levels of exposure. These results warrant further investigation of blue light as a novel decontamination strategy for the nosocomial environment, as well as additional wider decontamination applications.IMPORTANCE Blue light shows great promise as a novel decontamination strategy for the nosocomial environment, as well as additional wider decontamination applications (e.g., wound closure during surgery). This warrants further investigation.

Review of the Comparative Susceptibility of Microbial Species to Photoinactivation Using 380–480 nm Violet‐Blue Light

“…This was demonstrated by Halstead et al . who showed variations in the inactivation of isolates from an English hospital exposed to 400 nm light. Variation in dose requirements was particularly notable in clinical isolates of Stenotrophomonas maltophilia , with between 2.97 and 7.33 log 10 reduction achieved following a dose of 108 J cm −2 .…”

“… who showed variations in the inactivation of isolates from an English hospital exposed to 400 nm light. Variation in dose requirements was particularly notable in clinical isolates of Stenotrophomonas maltophilia , with between 2.97 and 7.33 log 10 reduction achieved following a dose of 108 J cm −2 . Very few of the organisms tested in the 79 studies reviewed have also been multidrug‐resistant (MDR) strains; however, dose requirements do seem to be similar between antibiotic sensitive and antibiotic‐resistant organisms.…”

Vaccination with a live attenuated Acinetobacter baumannii deficient in thioredoxin provides protection against systemic Acinetobacter infection

“…Furthermore, with the continued use of antibiotics, multi-, extensively-, and pan-drug resistant strains have begun to emerge [30] making therapy difficult and necessitating the need for alternative treatment options. Numerous antibiotic alternatives have been described including blue-light therapy [31, 32], nanoparticle [33, 34] and vaccine [13–17] therapies. While all of these proposed therapies have shown promise in animal models, vaccination offers long term prevention and can be administered to individuals living in or visiting endemic areas.…”

Antimicrobial blue light inactivation of pathogenic microbes: State of the art

“…Halstead et al (Halstead et al, 2016) recently assessed the effect of aBL at 400 nm from a light-emitting diode (LED) array on 34 bacterial strains commonly causing HAI, including Acinetobacter baumannii, Enterobacter cloacae, Stenotrophomonas maltophilia, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Enterococcus faecium, Klebsiella pneumoniae , and Elizabethkingia meningoseptica . All the bacteria in phosphate-buffered saline (PBS) suspensions were found to be susceptible to aBL inactivation, with the majority (71%) demonstrating a >5-log 10 decrease in colony-forming units (CFU) after exposures of 54 to 108 J/cm 2 aBL.…”

“…cloacae , S. maltophilia, P. aeruginosa, E. coli, S. aureus, E. faecium, K. pneumoniae, and E. meningoseptica (Halstead et al, 2016). Biofilms were formed by seeding bacterial suspensions in 96-well microtiter plates and incubating at 33 °C for 72 h. After an exposure of 216 J/cm 2 aBL at 400 nm, 34.6–96.4% reduction in the viability of bacteria in biofilms was observed depending on the bacterial strains.…”