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Download Use of volatile additives to increase the antimicrobial
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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 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 Bioelectrostatics Research Centre 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 Bioelectrostatics Research Centre 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 Bioelectrostatics Research Centre 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 • 50l of either ethyl alcohol, cinnamon oil or tea tree oil • Mean cfu counts compared • Standardised to 250 Bioelectrostatics Research Centre • 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 Bioelectrostatics Research Centre 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 Bioelectrostatics Research Centre 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 Bioelectrostatics Research Centre 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. Bioelectrostatics Research Centre 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 Bioelectrostatics Research Centre
