Use of volatile additives to increase the antimicrobial efficacy of a corona discharge

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Use of volatile additives to increase the
antimicrobial efficacy of a corona discharge

• Dr Lindsey Gaunt
• Bioelectrostatics Research Centre
• School of Electronics and Computer Science
• University of Southampton, UK

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Use of volatile additives to increase the
antimicrobial efficacy of a corona discharge

• Aim rationale
• Methods
• Results
• Discussion
• Applications and further work

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Introduction

• Electrical discharges historically used in
  disinfection.
• Intense plasma exposure for surface disinfection
• Broad spectrum sterilisation of biological media
  and surfaces
• Reactive oxygen species oxidise membrane
  macromolecules
• Electrical corona in nitrogen
• Effective concentration of ions and charged
  particles

• Enhance effects using volatile additives
  including essential oils

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Methods

• Test organisms were Escherichia coli and
• Staphylococcus aureus
• Enclosed booths of 0.5m3
• E. coli exposed for 30 minutes, S. aureus exposed
  for 10 minutes
• Agar plates

S. aureus
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Methods (cont.)

• Electrical corona driven ion wind
• Fan non-ionised air flow
• Control unexposed plates
• Current at plate of 10pA and ozone concentration
  of 0.2ppm
• 50?l of either ethyl alcohol, cinnamon oil or tea
  tree oil

• Mean cfu counts compared
• Standardised to 250
• Mann-Whitney-U tests

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Survivorship of E. coli following exposure to
ionised and non-ionised regimes

• Non-ionised air and cinnamon had no effects
• Viability was reduced by ethyl alcohol (19) and
  tea tree oil (45)
• Ionisation reduced viability by 65
• Mortality was increased to 89 with addition of
  ethyl alcohol and 92 with cinnamon oil
• Tea tree oil reduced ionic efficacy

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Survivorship of S. aureus following exposure to
ionised and non-ionised regimes

• Non-ionised air reduced viability by 23
• Ethyl alcohol and cinnamon oil reduced viability
  by 28 and 45 respectively
• Ionisation reduced viability by 74
• Mortality was increased to 82 with addition of
  either ethyl alcohol or cinnamon oil

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Summary
Ionised
Non-ionised
Air
No effect
Air
Ionic action
E. coli least susceptible
Volatiles
Volatiles
Vapour action
Ionised volatiles
Oils increased efficacy esp. E. coli
Cinnamon oil no effect vs. E.coli
Tea tree oil reduced ionic disinfection
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Conclusion

• Enhanced antibacterial activity through a
  reaction in the corona discharge with volatile
  molecules
• Additive effect seen between ionic and volatile
  disinfection (ethyl alcohol and cinnamon oil (E.
  coli))
• Tea tree oil generates less effective species
• Gram-negative bacteria (E. coli) are less
  susceptible to ionisation and volatiles than
  Gram-Positive (S. aureus)
• Membrane damage invoked for ionic disinfection
  and essential oil effects treatments compliment
  each other.

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Applications and further work

• Proof of concept
• Aerial disinfection
• Optimise, characterise and scale up
• Pathogenic organisms
• Understand issues
• Heating, ventilation and air conditioning systems
• Protection for public buildings, offices, medical
  environments and animal rearing facilities