Transcript Use of volatile additives to increase the antimicrobial

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
Bioelectrostatics Research Centre
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
E. coli
• 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
S. aureus
• Agar plates
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Methods (cont.)
• Electrical corona driven ion
wind
Ground electrode
• Fan – non-ionised air flow
Mini crucible for
• Control – unexposed plates
volatiles
150mm
• Current at plate of 10pA and
Direction of air flow
ozone concentration of 0.2ppm
Bacterial plate
• 50l of either ethyl alcohol,
cinnamon oil or tea tree oil
• Mean cfu counts compared
• Standardised to 250
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• Mann-Whitney-U tests
Corona electrode
Survivorship of E. coli following exposure to
ionised and non-ionised regimes
• Non-ionised air and
cinnamon had no effects
300
• Viability was reduced by
ethyl alcohol (19%) and
tea tree oil (45%)
200
150
• Ionisation reduced
viability by 65%
100
50
control
non-ionised
Ionised
Cinnamon
oil
Tea tree
oil
Ethyl
Alcohol
Alone
Cinnamon
oil
Tea tree
oil
Ethyl
Alcohol
0
Alone
Mean CFU
250
• 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%
300
• Ethyl alcohol and
cinnamon oil reduced
viability by 28% and
45% respectively
200
150
100
• Ionisation reduced
viability by 74%
50
control
non-ionised
Ionised
Cinnamon
oil
Ethyl
Alcohol
Alone
Cinnamon
oil
Ethyl
Alcohol
0
Alone
Mean CFU
250
• Mortality was increased
to 82% with addition of
either ethyl alcohol or
cinnamon oil
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Summary
Non-ionised
No effect
Air
Ionised
Air
Ionic action
E. coli least
susceptible
Volatiles
Volatiles
Vapour action
Cinnamon oil no
effect vs. E.coli
Ionised volatiles
Oils increased efficacy
esp. 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
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