Influence of Dielectric-barrier Discharge (DBD) Cold Plasma on Water Contaminated Bacteria

Abstract

Background and Aim: Dielectric Barrier Discharge (DBD) cold plasma has efficient antibacterial activity on bacterial contamination at a short period of time and confirms its potential for routine used in clinical environment biodecontamination as an alternative to conventional disinfectant methods of water treatment. The goal of this study is to evaluated  in vitro effectiveness  of DBD cold plasma on clinically important opportunistic pathogens that identified from water samples which were: Legionella E.meningosepteca andS. paucimobilis growth and to study DBD effectiveness on survival bacterial cell after  treatment. Methodology: 100-200 cfu/ml of Seven different environmental bacterial isolates belong to Legionella (4 isolates) E.meningosepteca(one isolate) and S. paucimobilis (two isolates) at  species were subjected to eleven different exposure time of DBD cold plasma treatment rang from 15Sec to 300 Sec, and plated on suitable agar media. Results were quantified by viable count. Results: It was found that using of different time of DBD plasma against different bacterial species give increase reduction rate until reaching lethal time of each species, this reduction time was species and isolates dependent, that the two L. pneumophila isolates have elimination time  between 90 sec and 120 sec, while, S. paucimobilis two isolates need (75 -120) sec for total reduction and E. meningoseptica need only 45 sec for total destruction. The effect of sub-lethal dose of nonthermal DBD plasma on surviving bacterial cell on some virulence factors was studied for one isolate from each of L. pneumophila and S. paucimobilis. Results show that the ability of isolates for biofilm production was strongly reduced by these two isolates and the ability of tested isolates to produced protease, lipase and acid phosphatase enzymes   were eliminated after exposed to sub-lethal dose of DBD plasma. Conclusion: Nonthermal DBD plasma is effective in treatment of tested isolates for relatively short exposure time. These activity is strain depending and survival cell after plasma treatment loss it is ability to exhibit some virulence property.  From these investigations, it was proven that the DBD method was an effective and alternative application to conventional disinfectant methods of water treatment.