Eradication of single- and mixed-species biofilms of P. aeruginosa and S. aureus by pulsed streamer corona discharge cold atmospheric plasma
Aleksandra Lavrikova, Mário Janda, Helena Bujdáková, Karol Hensel
Abstract
Cold atmospheric plasma has recently gained much attention due to its antimicrobial effects. Among others, plasma has proven its potential to combat microbial biofilms. Yet, knowledge of complex network interactions between individual microbial species in natural infection environments of the biofilm as well as plasma–biofilm inactivation pathways is limited. This study reports the effects of a cold plasma generated by a pulsed streamer corona discharge in air on single- and mixed-species biofilms of P. aeruginosa and S. aureus . The plasma causes significant biofilm biomass reduction, bacteria inactivation, and alteration in intracellular metabolism. For single-species biofilms S. aureus is found more tolerant to plasma than P. aeruginosa , and mixed-species biofilms display higher tolerance of both bacteria to plasma than in single-species biofilms. A comparison between wet and dehydrated biofilms reveals reduced plasma efficacy in wet environments. Consequently, biofilm dehydration prior to the plasma treatment facilitates penetration of plasma reactive species leading to higher bacteria inactivation. The evaluation of plasma-generated gaseous reactive species reveals O 3 and NO 2 being dominant species contributing to the etching mechanism of the overall plasma anti-biofilm effect. Despite the strong anti-biofilm effect is obtained, the biofilm regrowth on the next day after plasma treatment implies on the inability of pulsed streamer corona discharge to permanently eradicate biofilms on a surface. The search for adequate plasma treatment conditions of biofilms remains crucial to avoid the appearance of more adaptive biofilms. • Single- and mixed-species bacterial biofilms are treated by cold plasma. • Generation of gas-phase reactive species is affected by a treated substrate. • Gaseous O 3 and NO 2 species contribute to the etching antibiofilm mechanism. • P. aeruginosa biofilms are fully inactivated in 90 s. • Biofilm regrowth on the next day shows the inadequacy of the plasma treatment only.