Fig. 4
Antimicrobial efficacy of the NTP treatment system. Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus biofilms grown for 72 h in the EBM and then subjected to control processes or non-thermal plasma treatment (n = 3 ± SD). Untreated = no treatment, tubing immediately sectioned for recovery. Applicator = control treated by advancing the applicator through the tubing at 100 mm min- 1 using the motorised advancer. Argon = control treated by advancing the applicator through the tubing at 100 mm min- 1 using the motorised advancer with the argon gas supply switched ON at a flow rate of 2.5 L min- 1. The argon control treatment resulted in a small but significant reduction in biofilm density likely as result of either direct gas pressure or the impact of desiccation of the top layer of bacteria as the gas dries out the surface. Plasma = non-thermal plasma treated by advancing the applicator through the tubing at 100 mm min-1 using the motorised advancer with the argon gas supply switched ON at a flow rate of 2.5 L min- 1 and ionised using a power setting of 80 W and duty cycle of 28%.
