Effect of non-thermal plasma on AHL-dependent QS systems and biofilm formation in Pseudomonas aeruginosa: Difference between non-hospital and clinical isolates

Non-thermal plasma (NTP), generated by DC cometary discharge with a metallic grid at atmospheric pressure, was used to eradicate biofilm of Pseudomonas aeruginosa from titanium alloy Ti-6Al-4V carriers. The NTP exposure may reduce the ability of signal molecules to cause quorum sensing (QS) response in P. aeruginosa and as a result, affect the production of virulence factors including biofilm formation. Two groups of P. aeruginosa were compared, namely strains isolated from the environment (non-hospital) and clinical isolates from hospital environment. For the non-hospital strains, the inhibition of QS systems, mediated mainly by N-acyl-homoserine lactone (AHL) signals, and decrease of total biofilm biomass were observed after the NTP treatment. After 60 minutes of exposure, almost complete eradication of biofilm (54 - 98%) was achieved. Compared to that, the NTP effect on the AHL levels was more pronounced in clinical isolates of P. aeruginosa, but eradication of the biofilm was not achieved. We conclude that NTP affected the AHL-dependent QS systems (las and rhl), which does not necessarily have to result in the regulation of virulence in clinical isolates.