In today's medical practice, there are a number of decontamination techniques for accidental and surgical wounds. These techniques consist of preoperative surgical scrub, intraoperative lavage with and without antimicrobials or antiseptics, systemic and local administration of antimicrobials, local antimicrobial depots, aseptic technique, and postoperative continuous–vacuum-suction drains. Despite use of these and good operative techniques, the surgical site infection rate is 3% to 5.8% in all procedures in dogs and cats, 2% to 6% in human elective orthopedic patients, 8.1% in clean orthopedic procedures in horses, and 0% to 50% in human open orthopedic wounds.1–4 Surgical site infection increases the length of hospitalization by a mean of 7.5 days and costs up to an extra $26,019/patient in human hospitals and is associated with high morbidity rates and costs in veterinary patients.5,6 These infections are often caused by hospital-acquired organisms, which are increasingly multidrug resistant. Antimicrobial resistance is an ever-growing concern in human and veterinary patients, with methicillin-resistant Staphlycoccus aureus and multi–drug-resistant gram-negative organisms becoming an increasing problem, especially in surgical site infections.4,7 For these reasons, it is important to continue development of better methods to increase bacterial killing and control contamination without development of bacterial resistance or suppression of the immune response of the surgical site.
Nonthermal plasma is produced by electric discharge in liquid or air and is referred to as the fourth state of matter.8,9 Commonly encountered plasmas are found in fluorescent light, electric welders, and lightning.9 The generation of plasma produces reactive media, ozone and radicals via excitation, dissociation and ionization of any gaseous or vaporous substance, and a visible glow.9
It has been known for the past century that the application of plasma produced in air by electric discharge can be used for sterilization.10 One theory of its action is that plasma kills cells by disruption of the cellular membrane or wall (ie, its etching mechanism).10–12 This is specific to nonthermal plasma disinfection. Bacteria are also vulnerable to the destructive reactions of toxic species in nonthermal plasma, such as UV radiation, energetic ions, and cytotoxic free radicals, as well as the electrostatic stress of charged particles.10,11,13,14,a To date, there is no widely accepted mechanistic explanation of bacterial killing by nonthermal plasma.15
Generation of nonthermal plasmas in a vacuum chamber at subatmospheric pressure has been used for more than 40 years as an alternative to ethylene oxide gas sterilization.b,c This system allows rapid, reliable sterilization of low-pressure–tolerant materials and does not pose any environmental risk or leave any toxic residues.16 Gas plasma appears to be the safest, easiest, and most efficacious method of sterilization available.6 The use of plasma at atmospheric pressure was limited, until the development of pulsed discharges, because of the high temperature caused by continuous plasma generation. With pulsed-discharge delivery, it is possible to generate plasma for a short time and create the necessary active molecular species at ambient pressure and temperature.10 Nonthermal atmospheric plasma would be inexpensive and convenient and could be used on materials that are not amenable to subatmospheric pressure, such as certain polymers, foodstuffs, and living tissues.17
Recently, nonthermal plasma has been investigated for its biomanipulation effect on cells. Living cells have several beneficial responses to plasma treatment, and short-term plasma treatment does not cause accidental cell death, which would exacerbate inflammation and tissue damage.13,18 One report19 suggested that the lethal dose of nonthermal plasma for bacteria is very low, compared with doses needed to harm living eukaryotic cells. Therefore, nonthermal plasma has been suggested as a possible decontaminant for infected wounds.19
The purpose of the study reported here was to determine the effect of nonthermal plasma on S aureus, fibroblasts in monolayer culture, and clean and contaminated skin explants. Our hypothesis was that the plasma-generating device would inhibit bacterial growth and have minimal negative effects on cultured fibroblasts and dermal explants.
Dulbecco modified Eagle medium
Ruan R, Chen P. Nonthermal plasma for livestock odor control. MS thesis, Department of Biosystems and Agricultural Engineering, University of Minnesota, Saint Paul, Minn, 1998.
STERRAD sterilization system, Johnson & Johnson, New Brunswick, NJ.
Plazlyte, Abtox Inc, Pleasanton, Calif.
Provided by Dr. Alan J. Nixon, Comparative Orthopedics Laboratory, Cornell University, Ithaca, NY.
Gibco, Grand Island, NY.
Eugster S, Schawalder P & Gaschn F, et al. A prospective study of postoperative surgical site infections in dogs and cats. Vet Surg 2004;33:542–550.
Benger JR, Kelly AJ, Winson IG. Does early wound infection after elective orthopaedic surgery lead on to chronic sepsis? J R Coll Surg Edinb 1998;43:43–44.
MacDonald DG, Morley PS & Bailey JV, et al. An examination of the occurrence of surgical wound infection following equine orthopaedic surgery (1981–1990). Equine Vet J 1994;26:323–326.
National Nosocomial Infections Surveillance System. National Nosocomial Infections Surveillance (NNIS) System report, data summary from January 1992 through June 2004, issued October 2004. Am J Infect Control 2004;32:470–485.
Southwood LL, Baxter GM. Instrument sterilization, skin preparation, and wound management. Vet Clin North Am Equine Pract 1996;12:173–194.
Weese JS. Methicillin-resistant Staphylococcus aureus in horses and horse personnel. Vet Clin North Am Equine Pract 2004;20:601–613.
Jacobs P, Kowatsch R. Sterrad sterilization system: a new technology for instrument sterilization. Endosc Surg Allied Technol 1993;1:57–58.
Laroussi M, Alexeff I, Kang WL. Biological decontamination by nonthermal plasmas. IEEE Trans Plasma Sci IEEE Nucl Plasma Sci Soc 2000;28:184–187.
Laroussi M, Richardson JP, Dobbs FC. Effects of nonequilibrium atmospheric pressure plasmas on the heterotropic pathways of bacteria and on their cell morphology. Appl Phys Lett 2002;81:772–774.
Mendis DA, Rosenberg M, Azam F. A note on the possible electrostatic disruption of bacteria. IEEE Trans Plasma Sci IEEE Nucl Plasma Sci Soc 2000;28:1304–1306.
Kieft IE, Broers JL & Caubet-Hilloutou V, et al. Electric discharge plasmas influence attachment of cultured CHO K1 cells. Bioelectromagnetics 2004;25:362–368.
Soloshenko IA, Tsiolko VV & Khomich VA, et al. Features of sterilization using low-pressure DC-discharge hydrogen-peroxide plasma. IEEE Trans Plasma Sci IEEE Nucl Plasma Sci Soc 2002;30:1440–1444.
Laroussi M. Nonthermal decontamination of biological media by atmospheric-pressure plasmas: review, analysis, and prospects. IEEE Trans Plasma Sci IEEE Nucl Plasma Sci Soc 2002;30:1409–1415.
Geiss HK. New sterilization technologies—are they applicable for endoscopic surgical instruments? Endosc Surg Allied Technol 1994;2:276–278.
Stoffels E, Flikweert AJ & Stoffels WW, et al. Plasma needle: a non-destructive atmospheric plasma source for fine surface treatment of (bio)materials. Plasma Sources Sci Technol 2002;11:383–388.
Stoffels E, Kieft E & Sladek EJ, et al. Towards plasma surgery: plasma treatment of living cells, in Proceedings. 22nd Summer Sch Int Symp Phys Ionized Gases 2004;309–314.
Sosnin EA, Stoffels E & Erofeev MV, et al. The effects of UV irradiation and gas plasma treatment on living mammalian cells and bacteria: a comparative approach. IEEE Trans Plasma Sci IEEE Nucl Plasma Sci Soc 2004;32:1544–1549.
Oda T, Yamaji K, Takahashi T. Decomposition of dilute trichloroethylene by nonthermal plasma processing—gas flow rate, catalyst, and ozone effect. IEEE Trans Ind Appl 2004;40:430–436.