Antimicrobial Blue Light for Prevention and Treatment of Highly Invasive Vibrio vulnificus Burn Infection in Mice

Abstract

Vibrio vulnificus is an invasive marine bacterium that causes a variety of serious infectious diseases. With the increasing multidrug-resistant variants, treatment of V. vulnificus infections is becoming more difficult. In this study, we explored antimicrobial blue light (aBL; 405 nm wavelength) for the treatment of V. vulnificus infections. We first assessed the efficacy of aBL against five strains of V. vulnificus in vitro. Next, we identified and quantified intracellular porphyrins in V. vulnificus to provide mechanistic insights. Additionally, we measured intracellular reactive oxygen species (ROS) production and bacterial membrane permeabilization following aBL exposures. Lastly, we conducted a preclinical study to investigate the efficacy and safety of aBL for the prevention and treatment of burn infections caused by V. vulnificus in mice. We found that aBL effectively killed V. vulnificus in vitro in both planktonic and biofilm states, with up to a 5.17- and 4.57-log10 CFU reduction being achieved, respectively, following an aBL exposure of 216 J/cm2. Protoporphyrin IX and coproporphyrins were predominant in all the strains. Additionally, intracellular ROS was significantly increased following aBL exposures (P < 0.01), and there was evidence of aBL-induced permeabilization of the bacterial membrane (P < 0.0001). In the preclinical studies, we found that female mice treated with aBL 30 min after bacterial inoculation showed a survival rate of 81% following 7 days of observation, while only 28% survival was observed in untreated female mice (P < 0.001). At 6 h post-inoculation, an 86% survival was achieved in aBL-treated female mice (P = 0.0002). For male mice, 86 and 63% survival rates were achieved when aBL treatment was given 30 min and 6 h after bacterial inoculation, respectively, compared to 32% survival in the untreated mice (P = 0.0004 and P = 0.04). aBL did not reduce cellular proliferation or induce apoptosis. We found five cytokines were significantly upregulated in the males after aBL treatment, including MCSF (P < 0.001), MCP-5 (P < 0.01), TNF RII (P < 0.01), CXCL1 (P < 0.01), and TIMP-1 (P < 0.05), and one in the females (TIMP-1; P < 0.05), suggesting that aBL may induce certain inflammatory processes. In conclusion, aBL may potentially be applied to prevent and treat V. vulnificus infections.

Blue Light Potentiates Antibiotics in Bacteria via Parallel Pathways of Hydroxyl Radical Production and Enhanced Antibiotic Uptake

“…Previous studies have suggested and validated the production of ROS during aBL exposure. [7,9,19,20] In our study, however, we delved deeper into the mechanism of • OH radical production and its impact on bacterial viability. We determined that mutant strains that have increased intracellular non-chelated iron were more susceptible to killing by aBL.…”

“…Mice were then returned to their housing for a further 24 h, prior to euthanizing the mice, and isolating the infected skin tissue for subsequent homogenization, using Lysing Matrix D tubes (MP Biomedicals, USA) within a homogenizer (FastPrep-24™ Biomedicals, USA) and CFU determination. [7] Histological and Immunohistochemical Studies: The cell proliferation and apoptosis activity following blue light combined with chloramphenicol were assessed in naïve mice skin. In brief, 0.1% chloramphenicol solution (200 μL) was applied to the skin 30 min previously to the light exposure to allow complete penetration.…”

“…In the age of antimicrobial resistance, it is now more important than ever to identify strategies that adequately control infectious microbicidal activity is via the excitation of endogenous porphyrins that induce reactive oxygen species (ROS) production. [7,13,14] This in turn elicits damages within the microbial cell, leading to cell death.…”

“…Specifically, we have been exploiting antimicrobial blue light (aBL), a “drug‐free” approach which has been demonstrated to be a potent microbicide, capable of eliminating a myriad of infectious agents both in vitro and in vivo. [ 6–9 ] It has the benefit of killing microbes safely, rapidly, and without the risk of resistance development. [ 10,11 ] However, like any light‐based antimicrobial method, an inescapable drawback of aBL relates to the longevity of its microbicidal effects, which are known to be short lived, [ 6,9 ] due to the short‐term lifespan of reactive oxygen species (ROS).…”

“…[ 12 ] The common hypothesis for how aBL elicits its microbicidal activity is via the excitation of endogenous porphyrins that induce reactive oxygen species (ROS) production. [ 7,13,14 ] This in turn elicits damages within the microbial cell, leading to cell death.…”