In vitro antimicrobial effects and mechanism of air plasma‐activated water on Staphylococcus aureus biofilm

Abstract

The deactivation effects and mechanism of plasma‐activated water (PAW) against Staphylococcus aureus biofilm and the inhibitory effect on the biofilm regrowth capacity for the surviving S. aureus post PAW treatment were investigated in vitro. Systematic measurements on bacterial cultivability, metabolic capacity, membrane integrity and intracellular reactive oxygen species (ROS) concentration under two different experimental categories were carried out after PAW treatment. Considerable deactivation effects were discovered on biofilm S. aureus on both prolonging the PAW inducement or treatment time. The rising concentration of intracellular ROS and the PAW‐contained RS might exert synergistic effects in deactivating the biofilm S. aureus. Moreover, the biomass, bacterial cultivability and metabolic capacity of the regrown S. aureus biofilm all significantly declined along with the increasing PAW inducement or treatment time. Therefore, except for the short‐term rapid inactivation effects on the biofilm, the PAW treatment could also exert long‐term inhibitory effects on the regeneration of S. aureus biofilm.

Antimicrobial effects of airborne acoustic ultrasound and plasma activated water from cold and thermal plasma systems on biofilms

“…But biofilms by nature are complex biomaterials, (i) the biofilm architecture and (ii) its composition may limit penetration of reactive species into the biofilm matrix. Many previous studies demonstrated, that increasing treatment time and contact period could improve plasma inactivation efficacy against bacterial biofilm [30][31][32][33] . However, in this study PAW was combined with airborne acoustic ultrasound technology in order to obtain higher inactivation efficacies.…”

“…While the biofilm is dispersing the remaining cells are exposed to RONS and become more susceptible to be inactivated by PAW. The reactive species generated in PAW not only affects the cell membrane integrity but also penetrate into membrane channels and provoke reactive oxygen species (ROS) production endogenously which account for the intracellular ROS accumulation inside the cell 31 , 38 . Studies by Lukes et al 39 and Xu et al 31 also demonstrated that RONS interact with intracellular components (DNAs, proteins, lipids) and influence its metabolic responses in microorganisms.…”

“…The reactive species generated in PAW not only affects the cell membrane integrity but also penetrate into membrane channels and provoke reactive oxygen species (ROS) production endogenously which account for the intracellular ROS accumulation inside the cell 31 , 38 . Studies by Lukes et al 39 and Xu et al 31 also demonstrated that RONS interact with intracellular components (DNAs, proteins, lipids) and influence its metabolic responses in microorganisms. These interactions cause oxidative stress on cell components thus initiating lipid and protein peroxidation on the cell membrane, followed by protein and/or DNA damage and cell death 36 .…”

Plasma-Activated Water (PAW) as a Disinfection Technology for Bacterial Inactivation with a Focus on Fruit and Vegetables

“…The effects of PAW on biofilms have also been explored. A study by Xu et al [ 63 ] indicated that both the plasma inducement time and the plasma treatment time could affect the bacterial cells in their ability to generate biofilms. Apart from more than 5 log 10 CFU/unit reduction of S. aureus cells in the biofilm, the regrowth capacity of the surviving cells was reduced by 30% as compared with the untreated cells [ 63 ].…”

“…A study by Xu et al [ 63 ] indicated that both the plasma inducement time and the plasma treatment time could affect the bacterial cells in their ability to generate biofilms. Apart from more than 5 log 10 CFU/unit reduction of S. aureus cells in the biofilm, the regrowth capacity of the surviving cells was reduced by 30% as compared with the untreated cells [ 63 ]. This effect is postulated as a result of regulation of genes ( SarA , IcaA , SigB , Rbf , LuxS ) involved in biofilm formation, especially in response to disinfectants such as hydrogen peroxide.…”