Investigation in the antimicrobial impact of cold plasma on wet and dry microorganisms

(Background) Cold atmospheric plasma is attracting more and more attention due to its gentle antimicrobial properties, which might enable many future medical and food applications. However, some microorganisms and application scenarios have not yet been investigated. Therefore, this study aims to investigate the effect of plasma on contaminated liquid films and dried surfaces.

(Methods) The experiments were performed with the nearfield module of a Piezobrush 3 plasma pen on the bacteria Staphylococcus carnosus, Pseudomonas fluorescens and Streptococcus vestibularis, as well as the yeast Candida auris. Additionally, the plasma emissions were measured with a spectrometer.

(Results) It was observed that in the liquid films the examined gram-positive bacterial strain was more sensitive to the plasma than the gram-negative bacteria and all bacteria were more sensitive than the yeast. In contrast to this, there was no significant difference between C. auris and S. carnosus on dried surfaces. The plasma exhibited strong UVA and UVB emissions and only weak emissions in the UVC range. However, a careful analysis revealed that the antimicrobial impact of the UVC should be about one order of magnitude above the UVA and UVB emissions.

(Conclusion) Further investigations are necessary to understand the differences and similarities between the impact of plasma on bacteria and yeast as well as the total contribution of the UV radiation to the antimicrobial impact of plasma.