Antimicrobial mechanism ofin-situplasma activated water treatment of pathogenicEscherichia coliandStaphylococcus aureusbiofilms

Aims This study investigated the efficacy and mechanisms of inactivation of against Escherichia coli UTI89 and Staphylococcus aureus NCTC8325 through an in-situ plasma-activated water (PAW) treatment.

and Results PAW was prepared by discharging atmospheric pressure cold plasma beneath the surface of sterile distilled water. The study investigated the inactivation of biofilm cells and biofilm matrix. A complete killing of biofilm cells was achieved on both of E. coli (6.76 ± 0.01 log CFU/mL) and S. aureus (6.82 ± 0.02 log CFU/mL). This process happened earlier in S. aureus. Simultaneously, PAW treatment disrupted the biofilm structure, inducing a significant reduction in general biofilm biomass and extracellular polymer substances (EPS) matrix. With the disruption of EPS, PAW was enabled to further interact with the bacterial membrane, causing a significant increase in membrane permeability and disrupted membrane structure. Finally, PAW treatment led to a significant accumulation of intracellular reactive oxygen and nitrogen species within the biofilm cells.

Collectively, these findings indicate that PAW effectively inactivates biofilms by mechanically targeting the biofilm EPS matrix and biofilm cells in both gram-negative and gram-positive bacteria. Impact statement This study contributes novel insights into plasma-activated water’s mechanisms of action, particularly its impact on the biofilm extracellular polymeric substances matrix (exopolysaccharides, extracellular DNA, and protein), cell membrane permeability, depolarization, and intracellular ROS and RNS accumulation in both of Gram-positive and Gram-negative species. These findings highlight PAW-based treatments against biofilm-related challenges in antimicrobial development and water system decontamination. Competing Interest Statement The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Author PJ Cullen is the CTO of PlasmaLeap Technologies, the supplier of the plasma power source and reactors employed in this study.