Antimicrobial Blue Light Inactivation of Gram-Negative Pathogens in Biofilms: In Vitro and In Vivo Studies

J Infect Dis. 2016 May 1;213(9):1380-7. doi: 10.1093/infdis/jiw070. Epub 2016 Feb 17.

Abstract

Background: Biofilms affect >80% bacterial infections in human and are usually difficult to eradicate because of their inherent drug resistance.

Methods: We investigated the effectiveness of antimicrobial blue light (aBL) (wavelength, 415 nm) for inactivating Acinetobacter baumannii or Pseudomonas aeruginosa biofilms in 96-well microplates or infected mouse burn wounds.

Results: In vitro, in 96-well microplates, exposure of 24-hour-old and 72-hour-old A. baumannii biofilms to 432 J/cm(2) aBL resulted in inactivation of 3.59 log10 and 3.18 log10 colony-forming units (CFU), respectively. For P. aeruginosa biofilms, similar levels of inactivation-3.02 log10 and 3.12 log10 CFU, respectively-were achieved. In mouse burn wounds infected with 5 × 10(6) CFU ofA. baumannii, approximately 360 J/cm(2) and 540 J/cm(2) aBL was required to inactivate 3 log10 CFU in biofilms when delivered 24 and 48 hours, respectively, after bacterial inoculation. High-performance liquid chromatography analysis revealed the presence of endogenous porphyrins in both A. baumannii and P. aeruginosa TUNEL assay detected no apoptotic cells in aBL-irradiated mouse skin at up to 24 hours after aBL exposure (540 J/cm(2)).

Conclusions: aBL has antimicrobial activity in biofilms ofA. baumannii and P. aeruginosa and is a potential therapeutic approach for biofilm-related infections.

Keywords: Acinetobacter baumannii; HPLC; Pseudomonas aeruginosa; TUNEL assay; antimicrobial blue light; biofilm; bioluminescence imaging; burn wound; endogenous porphyrins; mouse model.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Acinetobacter baumannii / radiation effects*
  • Animals
  • Apoptosis / radiation effects
  • Biofilms / radiation effects*
  • Burns / microbiology
  • Disease Models, Animal
  • Disinfection / methods*
  • Female
  • Gram-Negative Bacterial Infections / microbiology*
  • Light
  • Linear Models
  • Mice
  • Mice, Inbred BALB C
  • Optical Imaging
  • Pseudomonas aeruginosa / radiation effects*
  • Wound Infection / microbiology