Antibacterial efficacy of a novel plasma reactor without an applied gas flow against methicillin resistant Staphylococcus aureus on diverse surfaces

The use of nonthermal plasma in the clinic has gained recent interest, as the need for alternative or supplementary strategies are necessary for preventing multi-drug resistant infections. The purpose of this study was to evaluate the antibacterial efficacy of a novel plasma reactor based on a high current version of sliding discharge and operated by nanosecond voltage pulses without an applied gas flow. This modification is advantageous for both portability and convenience. Bacterial inactivation was determined within a chamber by direct quantification of colony Jing units. Plasma exposure significantly inhibited the growth of Escherichia coli and Staphylococcus epidermidis following a 1-min application (p < 0.001). S. epidermidis was more susceptible to the plasma after a 5-min exposure compared to E. coli. Temperature and pH measurements taken immediately before and after plasma exposure determined neither heat nor pH changes play a role in bacterial inactivation. Because of the notable effect on S. epidermidis, the effect of plasma exposure on several isolates and strains of the related opportunistic pathogen Staphylococcus aureus was quantified. While S. aureus isolates and strains were efficiently inactivated on an agar surface, subsequent testing on other clinically relevant surfaces demonstrated that the inactivation level, although significant, was reduced. This reduction appeared to depend on both the surface texture and the surface moisture content. These findings suggest this novel plasma source lacking an applied gas flow has potential application for surface bacterial decontamination.