Cold atmospheric plasma mediates antibiofilm activity and sensitisation to further plasma and antibiotic challenges against Staphylococcus aureus

Abstract Staphylococcus aureus biofilms pose significant challenges in clinical settings due to their growing resistance to conventional antibiotics. While cold atmospheric plasma (CAP) is known for its bactericidal effects, its impact on biofilm architecture and physiology, and subsequent antimicrobial susceptibility remains poorly understood. This study investigates the effects of CAP treatment on S. aureus biofilms. We demonstrate that CAP not only reduces biofilm but also disrupts biofilm architecture and alters bacterial cell morphology. Transcriptomic analysis reveals distinct gene expression profiles following treatments with CAP and hydrogen peroxide, one of its active components, highlighting unique stress responses. We further show that CAP treatment of S. aureus grown on agar plates sensitises bacteria to additional CAP exposure and induces genomic alterations involved in cell envelope integrity, defence mechanisms and DNA replication, recombination and repair. Importantly, CAP treatment enhances bacterial susceptibility to the topical antibiotic for wound care mupirocin. These findings provide novel insights into the mechanisms underlying CAP-mediated biofilm control and offer a promising strategy to potentiate existing antimicrobial therapies.