Antimicrobial Blue Light Inactivation of Microbial Isolates in Biofilms

Abstract

Background and Objectives Biofilms cause more than 80% of infections in humans, including more than 90% of all chronic wound infections and are extremely resistant to antimicrobials and the immune system. The situation is exacerbated by the fast spreading of antimicrobial resistance, which has become one of the biggest threats to current public health. There is consequently a critical need for the development of alternative therapeutics. Antimicrobial blue light (aBL) is a light‐based approach that exhibits intrinsic antimicrobial effect without the involvement of exogenous photosensitizers. In this study, we investigated the antimicrobial effect of this non‐antibiotic approach against biofilms formed by microbial isolates of multidrug‐resistant bacteria. Study Design/Materials and Methods Microbial isolates of Acinetobacter baumannii, Candida albicans, Escherichia coli, Enterococcus faecalis, MRSA, Neisseria gonorrhoeae, Pseudomonas aeruginosa, and Proteus mirabilis were studied. Biofilms were grown in microtiter plates for 24 or 48 hours or in the CDC biofilm reactor for 48 hours and exposed to aBL at 405 nm (60 mW/cm2, 60 or 30 minutes). The anti‐biofilm activity of aBL was measured by viable counts. Results The biofilms of A. baumannii, N. gonorrhoeae, and P. aeruginosa were the most susceptible to aBL with between 4 and 8 log10 inactivation after 108 J/cm2 (60 mW/cm2, 30 minutes) or 216 J/cm2 (60 mW/cm2, 60 minutes) aBL were delivered in the microplates. On the contrary, the biofilms of C. albicans, E. coli, E. faecalis, and P. mirabilis were the least susceptible to aBL inactivation (−0.30, −0.24, −0.84, and −0.68 log10 inactivation, respectively). The same aBL treatment in biofilms developed in the CDC biofilm reactor, caused −1.68 log10 inactivation in A. baumannii and −1.74 and −1.65 log10 inactivation in two different strains of P. aeruginosa. Conclusions aBL exhibits potential against pathogenic microorganisms and could help with the significant need for new antimicrobials in clinical practice to manage multidrug‐resistant infections. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Biofilms as Promoters of Bacterial Antibiotic Resistance and Tolerance

“…Good examples of these methods include nanoparticles, sonication, irradiation (ultraviolet, visible, or infrared light), or biomaterials. Indeed, blue light, for example, was effective against biofilms formed by A. baumannii , P. aeruginosa , and N. gonorrhoeae although less so against biofilms of E. coli and E. faecalis [ 311 ]. In vivo studies in mouse burns showed that blue-light exposure could drastically reduce bacterial load and effectively protect mice from lethal infection with P. aeruginosa [ 312 ].…”

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

“…For example, blue light (405 nm; 108–206 J/cm 2 ) significantly inactivated monomicrobial biofilms of drug-resistant A. baumannii , P. aeruginosa and Neisseria gonorrhoeae (4–8 log CFU/mL; p < 0.01 or p < 0.0001), whereas the same blue light treatment did not significantly affect the biofilms of E. coli , E. faecalis and Proteus mirabilis . Further, blue light (405 nm; 216 J/cm 2 ) significantly reduced ( p < 0.01) the number of MRSA in biofilms grown for 24 h, but not in biofilms grown for 48 h [ 250 ].…”

Staphylococcus aureus growth delay after exposure to low fluencies of blue light (470 nm)

“…Photobiomodulation using blue light has been largely discussed as an alternative antimicrobial therapy. It shows positive results on in vitro experiments and demonstrates advantages as a treatment when compared with photodynamic therapy and ultraviolet light (Guffey and Wilborn, 2006;Enwemeka et al, 2008Enwemeka et al, , 2009Chui et al, 2012;De Lucca et al, 2012;Bumah et al, 2013Bumah et al, , 2015Dai et al, 2013;Kim et al, 2013;Pileggi et al, 2013;Sousa et al, 2015;Masson-Meyers et al, 2015;Rosa et al, 2016;Ferrer-Espada et al, 2019;Meurer et al, 2019;Rupel et al, 2019;Schmid et al, 2019). Nevertheless, the great variety of experimental protocols using blue light on bacterial inhibition creates difficulty to identify ideal light emission parameters to be adopted with confidence.…”

“…Staphylococcus aureus (S. aureus) is a Gram-positive aerobic bacterium, which presents a highly evolved capacity of developing resistance to antimicrobial drugs. Additionally, it is an important etiological agent in skin wound contaminations, often evolving to generalized infections (Enwemeka et al, 2009;Bumah et al, 2013Bumah et al, , 2015Sousa et al, 2015;Freitas et al, 2018;Ferrer-Espada et al, 2019;Rupel et al, 2019).…”

“…Photobiomodulation using wavelength between violet and blue spectrum (405-470 nm) has been receiving great attention in the last decade and is considered an example of antibacterial therapy. Thus, the effect of blue light on different species of bacteria has been the subject of several studies (Feuerstein, 2012;Bumah et al, 2013;Dai et al, 2013;Guffey et al, 2013;Sousa et al, 2015;Wang et al, 2017, Ferrer-Espada et al, 2019Meurer et al, 2019;Rupel et al, 2019;Schmid et al, 2019). The blue light antimicrobial effect has been observed using different experiment protocols, however, the true mechanism of action is still not fully understood (Chui et al, 2012;Dai et al, 2013;Bumah et al, 2015;Wang et al, 2017;Rupel et al, 2019;Schmid et al, 2019).…”