We studied the efficacy of cold atmospheric-pressure plasma (CAP), generated by a two-dimensional array of integrated, coaxial, microhollow, dielectric barrier discharge plasma, against Salmonella enterica serovar Heidelberg (SH) on stainless steel, romaine lettuce, and chicken breast. Exposure of SH to CAP on a dry stainless steel surface had low bactericidal efficacy; only 2.5 log10 colony-forming units (CFUs) were inactivated after 10 min of exposure. On the other hand, the presence of moisture led to decontamination of ∼6.5 log10 CFUs after only 3 min. Although complete decontamination was not achieved on lettuce and chicken breast samples after 10 min of exposure, SH counts were reduced by ∼4.5 and 3.7 log10 CFUs, respectively. A partial suppression of bactericidal effects was observed on steel surfaces when it was coated with bovine serum albumin before spiking with bacteria and exposure to plasma, indicating that the proteinaceous nature of chicken meat may be partially responsible for lower efficacy of CAP on chicken muscles. The initial bacterial load was also found to affect the anti-SH efficacy; at high (∼6.5 log CFUs) and low (∼3.5 CFUs) initial counts, the time required for complete decontamination on stainless steel and lettuce decreased from 3 to 0.5 min and >10 to 1 min, respectively. However, the analysis of inactivation kinetics showed that effects of initial loads of contamination on the rate of bacterial inactivation were not statistically significant. This is consistent with other findings for conditions where both bacterial loads were under the multilayering threshold that might have affected the rate of killing.
Keywords: 2D plasma setup; Salmonella enterica serovar Heidelberg; chicken breast muscle; cold plasma; lettuce; multidrug resistant Salmonella; stainless-steel.