Inactivation Effects of Non-Thermal Atmospheric-Pressure Helium Plasma Jet on Staphylococcus aureus Biofilms

The antimicrobial effects and mechanism of helium atmospheric-pressure plasma jet (APPJ) treatment on Staphylococcus aureus biofilms are evaluated in vitro. The S. aureus biofilms are more resistant to the plasma treatment than adherent bacteria. The APPJ-treated S. aureus biofilms disclose a depth/layer-related intra-bacterial ROS accumulation effect. Plasma exposure may induce bacterial oxidative stress and trigger the production of intracellular reactive oxygen species (ROS) in the biofilms, which possibly contributes to bacteria death in addition to direct etching from the exterior of bacteria. The findings provide insights into the mechanism of biofilm inactivation by plasma reactive species and plasma-induced intracellular ROS.