title: Control of methicillin-resistant Staphylococcus aureus in planktonic form and biofilms: a biocidal efficacy study of nonthermal dielectric-barrier discharge plasma.
abstract: BACKGROUND
  Bacterial contamination of surfaces with methicillin-resistant Staphylococcus aureus (MRSA) is a serious problem in the hospital environment and is responsible for significant nosocomial infections. The pathogenic contaminants form biofilms, which are difficult to treat with routine biocides. Thus, a continuous search for novel disinfection methods is essential for effective infection control measures. This demonstration of a novel technique for the control of virulent pathogens in planktonic form as well as in established biofilms may provide a progressive alternative to standard methodology.
  
  
  METHODS
  We evaluated a novel technique of normal atmospheric nonthermal plasma known as floating-electrode dielectric-barrier discharge (FE-DBD) plasma against a control of planktonic and biofilm forms of Escherichia coli, S aureus, multidrug-resistant methicillin-resistant S aureus (MRSA) -95 (clinical isolate), -USA300, and -USA400, using widely accepted techniques such as colony count assay, LIVE/DEAD BacLight Bacterial Viability assay, and XTT (2,3-Bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide) assay.
  
  
  RESULTS
  Exposure of free living planktonic forms of E coli, S aureus, and MRSA were rapidly inactivated by DBD plasma. Approximately 10(7) bacterial cells were completely (100%) killed, whereas 10(8) and 10(9) were reduced by approximately 90% to 95% and 40% to 45%, respectively, in less than 60 seconds (7.8 J/cm(2)) and completely disinfected in < or =120 seconds. In established biofilms, the susceptibility of MRSA USA400 was comparable with USA300 but less susceptible than MRSA95 (clinical isolate), S aureus, and E coli (P < .05) to FE-DBD plasma, and plasma was able to kill MRSA more than 60% within 15 seconds (1.95 J/cm(2)). The killing responses were plasma exposure-time dependent, and cell density dependent. The plasma was able disinfect surfaces in a less than 120 seconds.
  
  
  CONCLUSIONS
  Application of DBD plasma can be a valuable decontamination technique for the removal of planktonic and biofilm-embedded bacteria such as MRSA -USA 300, -USA 400, methicillin-sensitive S aureus (MSSA), and E coli, the more common hospital contaminants. Of interest, E coli was more resistant than S aureus phenotypes.
authors.affiliation: Surgical Infections Program, Department of Surgery, College of Medicine, Drexel University, 245 N 15th Street, Philadelphia, PA 19102, USA. Suresh.Joshi@Drexelmed.edu
authors.forename: Suresh G
authors.initials: SG
authors.lastname: Joshi
authors.forename: Michelle
authors.initials: M
authors.lastname: Paff
authors.forename: Gary
authors.initials: G
authors.lastname: Friedman
authors.forename: Greg
authors.initials: G
authors.lastname: Fridman
authors.forename: Alexander
authors.initials: A
authors.lastname: Fridman
authors.forename: Ari D
authors.initials: AD
authors.lastname: Brooks
mesh_terms: D018441:Biofilms; D004203:Disinfection / Q000379:methods*; D004560:Electricity; D004783:Environmental Microbiology; D004926:Escherichia coli / Q000502:physiology*; D006801:Humans; D050296:Microbial Viability; D013211:Staphylococcus aureus / Q000502:physiology*