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

Martina Paldrychová,Eliška Sembolová,Jan Masák,Vladimír Scholtz,Olga Mat’Átková,Jaroslav Julák,Eva Vaňková

doi:10.1063/1.5090451

Abstract

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.

Highlights

The microbicidal effects of non-thermal plasma (NTP) are generally known and its influence on bacteria, yeasts and microscopic fungi was described in a number of studies
The aim of our study was to evaluate the ability of Non-thermal plasma (NTP) to affect the surface growth, biofilm formation and acyl-homoserine lactone (AHL)-dependent quorum sensing (QS) systems of several strains of P. aeruginosa, both non-hospital and clinical isolates
The strains were studied in two experimental set-ups: the inhibition of surface growth on LB agar and the pre-formed biofilm eradication from titanium alloy Ti-6Al4V carriers coupled with evaluation of the interference of NTP with the AHL-dependent QS systems

Summary

Introduction

The microbicidal effects of non-thermal plasma (NTP) are generally known and its influence on bacteria, yeasts and microscopic fungi was described in a number of studies. The mechanisms of NTP action on microorganisms are widely discussed: it may be mediated by reactive oxygen and nitrogen species as ions, radicals, and stable or unstable electroneutral molecules; the participation of UV is considered. The stable particles persisting in exposed water give rise to so-called plasma activated water (PAW) (Lukeš et al, 2014; Julák et al, 2012; and Julák et al, 2018b). It turned out that microbial inactivation by NTP is possible by physicochemical processes, and by other mechanisms: in Ctvrtecková et al (2019) induced apoptosis in yeasts was described. The effects of NTP on inactivation, viability, growth or morphology of cells were studied for many times, e.g. The effects of NTP on inactivation, viability, growth or morphology of cells were studied for many times, e.g. Handorf et al (2018); Puligundla and Mok (2017); Patange et al (2019); Cheng et al (2016); and Duarte et al (2011)

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