Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2023

Treating infected wounds with plasma-activated water in vivo in mice (#222)

Adrian I Abdo 1 2 , Hang T Nguyen 1 2 , Thomas Schmitt-John 3 , Zlatko Kopecki 4 , David D Ogunniyi 5 , Katharina Richter 1 6
  1. Richter Lab, Basil Hetzel Institute for Translational Health Research, Adelaide, SA, Australia
  2. Department of Surgery, University of Adelaide, Adelaide, SA, Australia
  3. Plasmatreat GmbH, Steinhagen, Germany
  4. Future Industries Institute, University of South Australia, Adelaide, SA, Australia
  5. School of Animal and Veterinary Sciences, University of Adelaide, Adelaide, SA, Australia
  6. Institute of Photonics and Advanced Sensing, University of Adelaide, Adelaide, SA, Australia

Multidrug-resistant (MDR) bacterial infections are a mortal threat to anyone with a wound or requiring surgery. To combat MDR infections, it is imperative to adopt new antimicrobial approaches outside of antibiotics. One promising solution is cold plasma, a partially ionised gas enriched with reactive ions, free electrons and radicals. When applied to water (plasma-activated water; PW), a complex mixture of reactive oxygen and nitrogen species with low pH is produced that effectively kill microbes.

We previously demonstrated that PW effectively killed Gram-positive and -negative biofilms in vitro. We have now progressed to validating PW as a novel wound cleanser in vivo by testing the antimicrobial activity and wound healing effects using a bioluminescent methicillin-resistant Staphylococcus aureus (MRSA)-infected scald burn model in BALB/c mice.

Partial thickness dorsal skin scald wounds (69 mm2) were produced with 65 °C water exposure for 45 seconds. After two-day rest period, wounds were infected with 1×107 CFU bioluminescent MRSA for 24 hours to develop biofilm infection, then treated twice daily with 100 µL PW or water for 7 days. One uninfected burn group was included as a control. Wound size and bioluminescence were measured daily before treatment was applied. At day 8, mice (n=8/group) were euthanised and the wounds were harvested for bacterial count and histological analysis.

Daily bioluminescence measurements of wounds treated with PW had significantly reduced bacterial load compared to water-treated wounds from day 5 (p<0.05) and a significantly lower CFU count at day 8 (1.84 log[CFU] reduction; p=0.0151). Day 8 bioluminescence and CFU were highly correlated (Kendall’s τ=0.6759). Wound histology indicated that PW significantly improved re-epithelialisation by 38 % compared to the infection control (p=0.0159). Moreover, PW did not hinder wound closure, as there was no difference in wound length, dermal gap or epidermal thickness between treatment groups.

Overall, this demonstrates that PW exhibits promising antimicrobial activity and possibly improves wound healing. Next, equivalency studies with current wound cleansers are warranted to test PW as an antibiotic-free wound cleansing solution.