Cold atmospheric pressure plasma elimination of clinically important single- and mixed-species biofilms.
Mixed-species biofilms reflect the natural environment of many pathogens in clinical settings and are highly resistant to disinfection methods. An indirect cold atmospheric-pressure air-plasma system was evaluated under two different discharge conditions for its ability to kill representative Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa) pathogens. Plasma treatment of individual 24-h-old biofilms and mixed-species biofilms that contained additional species (Enterococcus faecalis and Klebsiella pneumoniae) was considered. Under plasma conditions that favoured the production of reactive nitrogen species (RNS), individual P. aeruginosa biofilms containing ca. 5.0 × 106CFU were killed extremely rapidly, with no bacterial survival detected at 15 s of exposure. Staphylococcus aureus survived longer under these conditions, with no detectable growth after 60 s of exposure. In mixed-species biofilms, P. aeruginosa survived longer but all species were killed with no detectable growth at 60 s. Under plasma conditions that favoured the production of reactive oxygen species (ROS), P. aeruginosa showed increased survival, with the lower limit of detection reached by 120 s, and S. aureus was killed in a similar time frame. In the mixed-species model, bacterial kill was biphasic but all pathogens showed viable cells after 240 s of exposure, with P. aeruginosa showing significant survival (ca. 3.6 ± 0.6 × 106CFU). Overall, this study shows the potential of indirect air plasma treatment to achieve significant bacterial kill, but highlights aspects that might affect performance against key pathogens, especially in real-life settings within mixed populations.
Department of Electrical Engineering and Electronics, University of Liverpool, Brownlow Hill, Liverpool L69 3GJ, UK; Department of Surface Engineering and Optoelectronics, Jožef Stefan Institute, Jamova cesta 39, 1000 Ljubljana, Slovenia.
Martina
M
Modic
Public Health England, Manor Farm Road, Porton Down, Salisbury SP4 0JG, UK.
Neil P
NP
McLeod
Public Health England, Manor Farm Road, Porton Down, Salisbury SP4 0JG, UK. Electronic address: mark.sutton@phe.gov.uk.
J Mark
JM
Sutton
Department of Electrical Engineering and Electronics, University of Liverpool, Brownlow Hill, Liverpool L69 3GJ, UK. Electronic address: jlwalsh@liverpool.ac.uk.
James L
JL
Walsh
D001274:Atmospheric Pressure; D018441:Biofilms / Q000187:drug effects*; D015169:Colony Count, Microbial; D004202:Disinfectants / Q000494:pharmacology*; D006090:Gram-Negative Bacteria / Q000187:drug effects* / Q000502:physiology; D006094:Gram-Positive Bacteria / Q000187:drug effects* / Q000502:physiology; D050296:Microbial Viability / Q000187:drug effects; D058626:Plasma Gases / Q000494:pharmacology*; D013997:Time Factors
D004202:Disinfectants; D058626:Plasma Gases
Cold plasma; Decontamination; ESKAPE pathogens; Mixed-species biofilms