Cold Plasma Inactivation of E. coli and S. aureus on Solid Surfaces for Infection Treatment

In this paper we present a novel plasma technology which generates the plasma at very low gas temperature, hence named cold plasma. The plasma has been used in medical applications such as sterilization of surfaces and more recently has been proposed as an alternative to sterilize infected wounds or food. Pathogenic bacteria found on surfaces such as food or human or animal skin exhibit a significant problem as they cause food borne illnesses and in the case of human infecting bacteria, they can cause severe wounds infections.  This research project aims to determine the efficient exposure conditions of using cold plasma for inactivation of each selected bacterium on solid surfaces and to determine the effect of cold plasma on bacterial post plasma treatment growth. The cold plasma was applied to strains of Escherichia coli ATCC 11775 and Satphylococcus aureus ATCC 25923 on agar plates and treated for various exposure times ( 30, 60,120 and 180 seconds). Colonies that were able to survive the 60 seconds of treatment were transferred to tryptic soy broth (TSB) and inoculated for 24 hrs. Results have showed  94-100 % of E. coli elimination after 120 seconds of treatment and a 98-100% of S. aureus elimination after 180 seconds of treatment. Preliminary results indicate that the growth of survival colonies after 60 seconds of treatment may not be affected since the readings from optical density (O.D.) and bacterial concentration (CFU/ml) over the incubation time remained the same for the control and the colonies treated with plasma.