Gram positive and Gram negative bacteria differ in their sensitivity to cold plasma

Abstract Cold atmospheric-pressure plasma (CAP) is a relatively new method being investigated for antimicrobial activity. However, the exact mode of action is still being explored. Here we report that CAP efficacy is directly correlated to bacterial cell wall thickness in several species. Biofilms of Gram positive Bacillus subtilis , possessing a 55.4 nm cell wall, showed the highest resistance to CAP, with less than one log 10 reduction after 10 min treatment. In contrast, biofilms of Gram negative Pseudomonas aeruginosa , possessing only a 2.4 nm cell wall, were almost completely eradicated using the same treatment conditions. Planktonic cultures of Gram negative Pseudomonas libanensis also had a higher log…