Blue Light Eliminates Community-Acquired Methicillin-ResistantStaphylococcus aureusin Infected Mouse Skin Abrasions

Abstract

Background and objective: Bacterial skin and soft tissue infections (SSTI) affect millions of individuals annually in the United States. Treatment of SSTI has been significantly complicated by the increasing emergence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) strains. The objective of this study was to demonstrate the efficacy of blue light (415 -10 nm) therapy for eliminating CA-MRSA infections in skin abrasions of mice. Methods: The susceptibilities of a CA-MRSA strain (USA300LAC) and human keratinocytes (HaCaT) to blue light inactivation were compared by in vitro culture studies. A mouse model of skin abrasion infection was developed using bioluminescent USA300LAC::lux. Blue light was delivered to the infected mouse skin abrasions at 30 min (acute) and 24 h (established) after the bacterial inoculation. Bioluminescence imaging was used to monitor in real time the extent of infection in mice. Results: USA300LAC was much more susceptible to blue light inactivation than HaCaT cells ( p = 0.038). Approximately 4.75-log 10 bacterial inactivation was achieved after 170 J/cm 2 blue light had been delivered, but only 0.29 log 10 loss of viability in HaCaT cells was observed. Transmission electron microscopy imaging of USA300LAC cells exposed to blue light exhibited disruption of the cytoplasmic content, disruption of cell walls, and cell debris. In vivo studies showed that blue light rapidly reduced the bacterial burden in both acute and established CA-MRSA infections. More than 2-log 10 reduction of bacterial luminescence in the mouse skin abrasions was achieved when 41.4 (day 0) and 108 J/cm

Photodynamic Therapy Using Systemic Administration of 5-Aminolevulinic Acid and a 410-nm Wavelength Light-Emitting Diode for Methicillin-Resistant Staphylococcus aureus-Infected Ulcers in Mice

“…Previously, irradiation with blue light at ∼50 J/cm 2 decreased the bacterial count of MRSA by nearly 1 log 10 -unit [27]–[29], but no previous investigation has employed a 410-nm LED for ALA-PDT targeting MRSA. We achieved favorable antibacterial activity against MRSA via ALA-PDT with a 410-nm LED.…”

The relative antimicrobial effect of blue 405 nm LED and blue 405 nm laser on methicillin-resistant Staphylococcus aureus in vitro

“…Our laboratory and others have shown repeatedly that blue light in the range of 400-470 nm has antimicrobial effects on a diverse group of bacteria including Propionibacterium acnes, Pseudomonas aeruginosa, Porphyromonas gingivalis, Helicobacter pylori, and methicillin-resistant Staphylococcus aureus (MRSA) [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. However, most of the studies in this area have been done with blue LEDs or photodynamic therapy involving the use of blue absorbing dyes, not laser diodes.…”

Blue Laser Inhibits Bacterial Growth of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa

“…There are scant studies demonstrating the effect of blue laser on bacterial control, and among the existing studies, few used this light spectrum in different bacterial species. [13][14][15][16][17][18][19] One of the few studies found in the literature using violet laser in bacterial cultures was the in vitro work performed by Guffey et al, 15 who combined wavelengths of 405 and 880 nm (1,3,5,10, and 20 J/cm 2 ) to find a dose-dependent effect for inhibiting P. aeruginosa and S. aureus in all dosages tested. In parallel, the same authors 14 conducted a similar study with violet and blue lasers at 405 and 470 nm (1, 3, 5, 10, and 15 J/cm 2 ) in P. aeruginosa and S. aureus, demonstrating inhibitory effects regarding both wavelengths.…”