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

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


Use of volatile additives to increase the antimicrobial efficacy of a corona discharge1
Use of volatile additives to increase the antimicrobial efficacy of a corona discharge

  • Aim; rationale

  • Methods

  • Results

  • Discussion

  • Applications and further work


Introduction

E. coli efficacy of a corona discharge

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


Methods
Methods efficacy of a corona discharge

  • Test organismswere 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


Methods cont

Corona electrode efficacy of a corona discharge

Ground electrode

Mini crucible for volatiles

150mm

Direction of air flow

Bacterial plate

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


Survivorship of efficacy of a corona dischargeE. 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


Survivorship of s aureus following exposure to ionised and non ionised regimes
Survivorship of efficacy of a corona dischargeS. 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


Summary
Summary efficacy of a corona discharge

Ionised

Non-ionised

No effect

Air

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


Conclusion
Conclusion efficacy of a corona discharge

  • 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.


Applications and further work
Applications and further work efficacy of a corona discharge

  • 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


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