Abstract
Cold plasma is a state of matter that contains a large number of particles that are electrically charged. Plasmas generate chemically reactive species and ultraviolet radiation making them useful in decontamination applications (Kong & Laroussi, 2003). Research regarding the inactivation of gram-positive bacteria by cold plasma has been studied by Laroussi et al (2003); however, there is limited research regarding the germicidal effectiveness of cold plasma on Geobacillus stearothermophilus and Bacillus cereus microorganisms. The purpose of this study was to determine if cold plasma technology inactivates Geobacillus stearothermophilus and Bacillus cereus vegetative cells and spores. This study consisted of 981 samples; 762 experimental samples exposed to cold plasma at various times and 291 controls. Experimental samples were inoculated and exposed either directly or indirectly/remotely to cold plasma. After exposure the samples were incubated for 12 to 16 hours and colony forming units (CFU) were quantified. The percentage kill and log concentration reductions were calculated from the CFU counts. Data was analyzed using one-way ANOVA, Kruskal Wallis and Tukey’s tests at the .05 level. There was a statistically significant difference in the inactivation of Geobacillus stearothermophilus vegetative cells for indirect exposure (p=.0001), direct exposure (p=.0013), as well as for Bacillus cereus vegetative cells and spores (p=.0001). Exposure of Geobacillus stearothermophilus spores to cold plasma demonstrated no statistically significant differences in inactivation for indirect exposure (p=.7208) and direct exposure (p=.0835). Results indicate that cold plasma exposure significantly inactivated Geobacillus stearothermophilus (vegetative) and Bacillus cereus; however, Geobacillus stearothermophilus spores were not significantly inactivated. Funding for this project was provided by ADHA IOH.
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