Inactivation ofCampylobacter jejuniwith Dielectric Barrier Discharge Plasma Using Air and Nitrogen Gases

Abstract

Air and nitrogen gas are commonly used feed gases for plasma generation and are economically useful in industrial applications. The two gases were compared in dielectric barrier discharge plasma for the inactivation of Campylobacter jejuni on an agar surface. Plasma treatment with nitrogen gas for 20 s did not yield any reduction (p>0.05) in viable cell count. However, a 0.8-log reduction (p<0.05) in colony-forming units (CFU) occurred when the nitrogen gas was supplemented with 2% (vol/vol) air. The use of air only, air supplemented with 2% (vol/vol) nitrogen, or oxygen only further decreased the viable cell counts by 0.7-1.7-log CFU (p<0.05). These results suggest that oxygen in plasma generation is critically important for the increased inactivation effect. Scanning electron microscopy analysis showed much cell debris including fragmented flagella in the sample exposed to air plasma, while no cell debris was found in the sample exposed to nitrogen plasma. In transmission electron microscopy analysis, many C. jejuni cells exposed to air plasma had truncated flagella with sharp bends, while the cells exposed to nitrogen plasma were normal, strongly suggesting that the air plasma can reduce the virulence of C. jejuni. A BacLight assay showed that air plasma damaged the cellular membrane (p<0.05), whereas nitrogen plasma did not after 5- or 20-s treatment. The damage to the membrane was consistent with the reduced viable cell count. Based on confocal microscopic analysis, the similar results were found by visualizing the fluorescent-dye-stained cells. In addition, the prolonged nitrogen plasma for 2 min also damaged many cellular membranes. This study shows that air, especially oxygen, is more effective and destructive than nitrogen and provides evidence that membrane damage may be a major mechanism for the inactivation of C. jejuni exposed to plasma.

Implementation of a Non-Thermal Atmospheric Pressure Plasma for Eradication of Plant Pathogens from a Surface of Economically Important Seeds

“…In spite of the cell disruption and the loss of bacterial viability, the thickness of P. aeruginosa biofilm was also significantly reduced post the DBD exposure [42]. Regarding planktonic cells, the herein presented data find confirmation in the study of Kim et al [43], who reported a bacterial membrane interruption in Campylobacter jejuni based on the BacLight assay after a five-second application of DBD, generated under an oxygen atmosphere, or two minutes of DBD, generated under a nitrogen atmosphere. So far, disorganization of the bacterial membrane post plasma treatment has been attributed to the impact of plasma-generated charged particles, i.e., ions and electrons [44].…”

“…This explains the TEM-visualized release of the inner cytoplasmic contents (Figure 6). Analogous effects of the DBD treatment towards human bacterial pathogens were described previously [36,[40][41][42][43]. For instance, the utilization of CLSM by Ziuzina et al [42] revealed that either the direct or indirect 300 s action of DBD led to the recording of strong propidium iodide-related signals from the plasma-treated biofilms of P. aeruginosa.…”

New insight into the residual inactivation of Microcystis aeruginosa by dielectric barrier discharge

“…Among various plasma techniques, the non-thermal atmospheric dielectric barrier discharge (DBD) may be a most promising one. In fact, non-thermal DBD has been widely applied in inactivation of pathogen 20 21 , chemical synthesis 22 , film deposition 23 , material surface modification 24 and etc. When plasma takes place either over the solution surface or in the solution, a variety of physical and/or chemical processes are initiated.…”

A Cold Plasma Technology for Ensuring the Microbiological Safety and Quality of Foods

“…A comparison of air and nitrogen gas in dielectric barrier discharge plasma for the inactivation of Campylobacter jejuni reported that nitrogen gas for 20 s did not yield any reduction (p > 0.05) in viable cell count. However, a 0.8-log reduction (p < 0.05) in colonyforming units (CFU) was observed when the nitrogen gas was supplemented with 2% (vol/vol) air [113]. Shi et al [114] noted that relative humidity, gas type, and treatment time are all significant on generated ozone concentration and aflatoxin degradation.…”