Inactivation And Anti-infection Effect Of Cold Plasma On Staphylococcus Aureus Biofilm

Chronic infections caused by microbes are closely related to the formation of bacterial biofilms,and infections caused by bacterial biofilms are often manifested as long and recurrent episodes.The current treatment of microbial infection is mainly dependent on antibiotics,but antibiotics and immune system can not effectively eradicate the biofilm.Meantime,the treatment of antibotics could induce antibotic resistance,which greatly increased the cost of therapy of microbial infections and seriously affected the quality of life of patients.It is therefore imperative to find a new way to effectively inactivate bacterial biofilms.In this study,the biofilm model of Staphylococcus aureus was established in vitro,and the inactivation effects and mechanisms of plasma and plasma active water on biofilm were studied.The results showed that Staphylococcus aureus biofilm was decreased by 0.97,1.6,2.47,4.71 orders of magnitude with plasma treatment for 0,2,4,6,8 min.With treatment of PAW that activated for 2,4,6 min to the Staphylococcus aureus biofilm,the number of bacteria contained in the biofilms was reduced by 0.74,2.87,3.56 orders of magnitude,respectively.Observing the plasma treated Staphyloccus aureus biofilm by fluorescence microscope and scanning electron microscope,found that the plasma treatment increased the membrane permeability of bacteria in the biofilm,caused the bacteria to shrink and deform,and finally made the bacteria rupture.The content of extracellular protein in the biofilm increased,the content of eDNA decreased gradually.Gas phase of plasma contained NO,N2,N+,N2+,He and O by annalysis of the emission spectromete,the concentration of the H2O2,nitric aci and nitrous acid detected in the liquid phase increased over time.The changes of the minimum eradicate concentration of norfloxacin,ciprofloxacin,rifampicin and vancomycin against Staphylococcus aureus biofilm were measured and the dynamics curve of the biofilm inactivation were analyzed.The results showed that plasma treatment of Staphylococcus aureus biofilm reduced MBEC concentrations of norfloxacin,ciprofloxacin,rifampicin and vancomycin to 1/8-1/4 of the untreated samples.Plasma combined antibiotics treatment of Staphylococcus aureus biofilm decreased2.59-3.71 orders of magnitude more than that treated by the plasma or antibiotic treatment alone.Based on the infection models of the skin wounds and abdominal infection with Staphylococcusaureus biofilm,the plasma treatment of wounds infections and the plasma activated water treatment of abdominal infection were studied.The results showed that after plasma treatment of skin wounds infection BALB/c mice with Staphylococcus aureus biofilm,the bacteria number of wounds decreased 2.44 orders of magnitude more than that treated by the plasma or antibiotic treatment alone,which significantly promoted the healing of the skin wounds.After plasma active water treateent of abdominal infection BALB/c mice with Staphylococcus aureus biofilm,the bacteria number in kidney decreased by 2.62 orders of magnitude,and the mouse survival rate increased 40%.This results showed that plasma and PAW can effectively inactivate Staphylococcus aureus biofilm,and provides an important experimental basis for the application of plasma and PAW in the treatment of skin wound infection and abdominal cavity infection in clinical medicine.