Synergistic antimicrobial effects of atmospheric pressure non-thermal argon plasma and ciprofloxacin antibiotic against multi-drug resistant P. aeruginosa biofilm

Abstract

Bacterial biofilm formation is regarded as the major cause of infection development, therapeutic failure, and antibiotic resistance. This study aimed to assess the synergistic antibiofilm potential of an atmospheric-pressure non-thermal argon plasma and ciprofloxacin (Cip) against multi-drug-resistant Pseudomonas aeruginosa. Bacterial biofilms were pre-treated with the non-thermal Ar-plasma and subsequently treated with Cip antibiotic. Then, the bacterial biofilm formation level and cell viability were investigated using crystal violet staining, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide, SEM, and fluorescence microscopy, respectively. It was found that a short-time (a few seconds) pretreating with Ar-plasma not only reduced bacterial biofilm formation but also significantly decreased the viability of the cells within the biofilm matrix. According to the results, treating with Cip alone reduced bacterial biofilms by 32%, while pretreatment with Ar-plasma for 5, 10, 30, 60, and 90 s and subsequent treatment with Cip reduced bacterial biofilms by 76%, 79%, 81%, 75%, and 88%, respectively. In addition, the viability of bacterial cells within the biofilm matrix reduced to 66% in Cip treated cells, while pretreating with Ar-plasma for 5, 10, 30, 60, and 90 s and then treating with Cip significantly decreased cell viability to 28%, 25%, 21%, 23%, and 15%, respectively. This concept opens a promising approach for the treatment of drug-resistant bacteria for decontamination of heat-sensitive materials and human tissues based on the combination of atmospheric-pressure non-thermal Ar-plasma and antibiotics.