Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2023

Assessing the Efficacy of Plasma Activated Water as a Pre-Treatment Strategy for Biofilm-Infected Chronic Wounds (#210)

Heema K N Vyas 1 2 , Binbin Xia 1 , David Alam 1 , Nicholas Gracie 3 , Joanna Rothwell 4 , Scott A Rice 5 , Dee Carter 2 4 , Patrick J Cullen 1 , Anne Mai-Prochnow 1
  1. School of Chemical and Biomolecular Engineering, The University of Sydney, Sydney, NSW, Australia
  2. The Sydney Institute for Infectious Diseases, The University of Sydney, Sydney, NSW, Australia
  3. School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW, Australia
  4. ARC Training Centre for Food Safety in the Fresh Produce Industry, The University of Sydney, Sydney, NSW, Australia
  5. Agriculture and Food, Microbiomes for One Systems Health, Commonwealth Scientific and Industrial Research Organisation, Sydney, NSW, Australia

Healing and treatment of chronic wounds is often complicated by biofilm formation. Plasma activated water (PAW) is a relatively new and underexplored anti-biofilm agent. Here, the efficacy of PAW as a pre-treatment strategy has been investigated prior to application of topical antimicrobials (polyhexamethylene biguanide, povidone iodine, and medical honey) routinely used for the treatment of chronic wounds. To ensure translation from lab to clinic, the eradicative efficacy of this treatment strategy has been investigated for Escherichia coli biofilms formed on both a plastic substratum and in an in vitro biofilm-skin epithelial cell model (comprising a human keratinocyte monolayer substratum). We demonstrated that PAW pre-treatment greatly increases the complete eradicative abilities of all three antimicrobials against E. coli biofilm formed on both the plastic and keratinocyte substratum. However, the efficacy of PAW-antimicrobial (and both PAW and antimicrobial alone) does decrease for biofilms formed in the in vitro biofilm-skin epithelial cell model. The mechanisms underpinning the anti-biofilm activity of PAW were also investigated. Ozone, hydroxyl radicals, superoxide anions, peroxynitrite anions, and peroxynitrous acid present within the PAW significantly impacted biofilm viability. Accumulation of reactive oxygen and nitrogen species (RONS) within biofilms treated with PAW was significant. Then, the membrane activity of the PAW was determined. Within 1 minute of PAW exposure, significant E. coli cell membrane effects were seen, namely via membrane depolarisation and increased outer membrane permeability. For the first time, we highlight the value of encompassing PAW as a pre-treatment strategy for biofilm-infected chronic wounds, whereby the anti-biofilm activity of routinely used topical antimicrobials is greatly enhanced. Moreover, complete E. coli biofilm eradication is achievable in a more clinically relevant in vitro biofilm-skin epithelial cell model. Mechanistically, we propose that PAW induces RONS to accumulate within the E. coli biofilms whilst enacting on the bacterial cell membrane, thereby potentiating the antibacterial effect of other antimicrobials.