Cold Plasma Effects on Biofilms

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    Harrison
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      Cold Plasma Kills Bacteria Better Than Antibiotics
      By Amy Dusto Sat Dec 18, 2010

      Before you ask whether that is an oxymoron, let me explain. Cold here is not cold in the Arctic sense; rather the opposite of scalding hot. Plasma — an ionized gas sometimes called the fourth state of matter — typically exists at thousands of degrees Celsius, and hot plasmas are regularly used to sterilizing surgical equipment.

      Cold plasmas are closer to room temperatures. And only recently have researchers been able to make plasmas at a steady 35 to 40 degrees Celsius and at atmospheric pressure. This is cold enough to touch safely — watch this woman on YouTube run her finger beneath a cold plasma flame.

      Svetlana Ermolaeva and her research team at the Gamaleya Institute of Epidemiology and Microbiology in Moscow wanted to see how well cold plasma could work against nasty microbes that lead to infections.They used a cold plasma torch in the lab to combat two common bacteria, Pseudomonas aeruginosa and Staphylococcus aureus, which show up frequently in wound infections, but are resistant to antibiotics because they have a protective layer called a biofilm.

      After five minutes, the plasma torch killed 99 percent of bacteria grown in a Petri dish, and after ten minutes, it killed 90 percent of bacteria present in the wounds of a rat wounds. And because the torch can be directed at a specific, small area of infection, surrounding tissue is left unharmed.

      “Cold plasmas are able to kill bacteria by damaging microbial DNA and surface structures without being harmful to human tissues. Importantly we have shown that plasma is able to kill bacteria growing in biofilms in wounds, although thicker biofilms show some resistance to treatment,” Ermolaeva said in a press release.

      The researchers published their results in the Journal of Medical Microbiology.

      Antibiotics, you may have met your match. Not only does cold plasma treatment avoid the nasty side effects that drugs often bring, but the ionized torch destroys bacteria indiscriminately — whether it is antibiotic-resistant or not. There is no escaping a plasma attack.
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      J Med Microbiol 60 (2011), 75-83; DOI: 10.1099/jmm.0.020263-0

      Bactericidal effects of non-thermal argon plasma in vitro, in biofilms and in the animal model of infected wounds

      Svetlana A. Ermolaeva1, Alexander F. Varfolomeev1, Marina Yu. Chernukha1, Dmitry S. Yurov1, Mikhail M. Vasiliev2, Anastasya A. Kaminskaya1, Mikhail M. Moisenovich3, Julia M. Romanova1, Arcady N. Murashev4, Irina I. Selezneva5, Tetsuji Shimizu6, Elena V. Sysolyatina1, Igor A. Shaginyan1, Oleg F. Petrov2, Evgeny I. Mayevsky5, Vladimir E. Fortov2, Gregor E. Morfill6, Boris S. Naroditsky1 and Alexander L. Gintsburg1

      Correspondence: Svetlana A. Ermolaeva sveta(at)ermolaeva.msk.su
      Received March 9, 2010 Accepted September 7, 2010

      Non-thermal (low-temperature) physical plasma is under intensive study as an alternative approach to control superficial wound and skin infections when the effectiveness of chemical agents is weak due to natural pathogen or biofilm resistance. The purpose of this study was to test the individual susceptibility of pathogenic bacteria to non-thermal argon plasma and to measure the effectiveness of plasma treatments against bacteria in biofilms and on wound surfaces. Overall, Gram-negative bacteria were more susceptible to plasma treatment than Gram-positive bacteria. For the Gram-negative bacteria Pseudomonas aeruginosa, Burkholderia cenocepacia and Escherichia coli, there were no survivors among the initial 105 c.f.u. after a 5 min plasma treatment.

      The susceptibility of Gram-positive bacteria was species- and strain-specific. Streptococcus pyogenes was the most resistant with 17 % survival of the initial 105 c.f.u. after a 5 min plasma treatment. Staphylococcus aureus had a strain-dependent resistance with 0 and 10 % survival from 105 c.f.u. of the Sa 78 and ATCC 6538 strains, respectively. Staphylococcus epidermidis and Enterococcus faecium had medium resistance. Non-ionized argon gas was not bactericidal. Biofilms partly protected bacteria, with the efficiency of protection dependent on biofilm thickness. Bacteria in deeper biofilm layers survived better after the plasma treatment. A rat model of a superficial slash wound infected with P. aeruginosa and the plasma-sensitive Staphylococcus aureus strain Sa 78 was used to assess the efficiency of argon plasma treatment.

      A 10 min treatment significantly reduced bacterial loads on the wound surface. A 5-day course of daily plasma treatments eliminated P. aeruginosa from the plasma-treated animals 2 days earlier than from the control ones. A statistically significant increase in the rate of wound closure was observed in plasma-treated animals after the third day of the course. Wound healing in plasma-treated animals slowed down after the course had been completed. Overall, the results show considerable potential for non-thermal argon plasma in eliminating pathogenic bacteria from biofilms and wound surfaces.

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