Antimicrobial Efficacy of Two Surface Barrier Discharges with Air Plasma against In Vitro Biofilms

Abstract

The treatment of infected wounds is one possible therapeutic aspect of plasma medicine. Chronic wounds are often associated with microbial biofilms which limit the efficacy of antiseptics. The present study investigates two different surface barrier discharges with air plasma to compare their efficacy against microbial biofilms with chlorhexidine digluconate solution (CHX) as representative of an important antibiofilm antiseptic. Pseudomonas aeruginosa SG81 and Staphylococcus epidermidis RP62A were cultivated on polycarbonate discs. The biofilms were treated for 30, 60, 150, 300 or 600 s with plasma or for 600 s with 0.1% CHX, respectively. After treatment, biofilms were dispensed by ultrasound and the antimicrobial effects were determined as difference in the number of the colony forming units by microbial culture. A high antimicrobial efficacy on biofilms of both plasma sources in comparison to CHX treatment was shown. The efficacy differs between the used strains and plasma sources. For illustration, the biofilms were examined under a scanning electron microscope before and after treatment. Additionally, cytotoxicity was determined by the MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay with L929 mouse fibroblast cell line. The cell toxicity of the used plasma limits its applicability on human tissue to maximally 150 s. The emitted UV irradiance was measured to estimate whether UV could limit the application on human tissue at the given parameters. It was found that the UV emission is negligibly low. In conclusion, the results support the assumption that air plasma could be an option for therapy of chronic wounds.

Randomized placebo-controlled clinical trial showed cold atmospheric argon plasma relieved acute pain and accelerated healing in herpes zoster

“…Plasma is also known to have antibacterial effects [6,[8][9][10] which may offer another advantage, reducing the risk of secondary infection in HZ.…”

“…CAPs have been shown to be safe and effective in reducing bacterial carriage in chronic infected wounds [8][9][10] and acute wounds [11], and may accelerate wound healing [12][13][14]. In single case reports, cold atmospheric argon plasma treatment has resulted in pain reduction in infected skin conditions [15,16].…”

Skin Wound Healing: An Update on the Current Knowledge and Concepts

“…3). Different studies gave evidence of the successful decontamination of multidrug-resistant, contaminated wounds through nonthermal plasma (NTP) or cold atmospheric plasma (CAP) [88,89,90]. A secondary beneficial feature of plasma derives from its genomic effects [91].…”

Oxy-nitroso shielding burst model of cold atmospheric plasma therapeutics

“…For example, in a recent study of the role of the Ar jet plasma þKINpenÿ in dermatology, investigators showed by skin histology and confocal microscopy that the apparent depth of altered skin (in the stratum corneum) was ~ 5-10 microns. [10][11][12] These authors suggest that the main effect of the plasma was due to oxidative radicals as a decrease in carotene antioxidants was observed. In some cases, deeper penetration was observed in the vicinity of hair follicles on the skin.…”