A practical technique for disinfecting electrical stimulation apparatuses used in wound treatment.

[Kalinowski DP, Brogan MS, Sleeper MD. A practical technique for disinfecting electrical stimulation apparatuses used in wound treatment. Phys Ther. 1996;76: 1340 -1347.]

Key Words: Aseptic technique, Disinfection, Electrical stimulation, Infection control, Wound treatment.

Electrical stimulation (ES) is widely used for pain management, muscle reeducation, edema reduction, and treatment of chronic wounds.[1] In wound treatment, ES involves the application of a low-level, therapeutic dose of electricity directly into the would.[2] Based on many experimental and clinical studies, a large body of literature provides compelling evidence that ES, when used for the treatment of certain wounds, is efficacious in promoting healing by enhancing tissue proliferation and repair[2-10] end by eliminating many microorganisms that might otherwise inhibit or prevent healing.[11-18]

The Agency for Health Care Policy and Research, a branch of the US Public Health Service, has recommended the use of ES in certain situations. In 1994, the Agency for Health Care Policy and Research cited in its guidelines for the treatment of decubitus ulcers that ES should be the first alternative treatment for a wound that has not responded to traditional care or that has shown only slow or minimal improvement.[19]

Proper use of ES in wound management requires that physical therapists understand variables associated with the modality, such as current form, intensity, duration, and frequency,[2] as well as methods pertaining to infection control.[20] We believe that most clinicians realize the importance of aseptic technique and disinfection in controlling infection. When ES is used by clinician outside of traditional hospital settings, such as subacute facilities, ambulatory care centers, and private practices, resources for sterilizing or disinfecting equipment may not be as extensive as those at larger facilities, such as hospitals (which traditionally have autoclaves). With patients being treated outside of traditional hospital settings, clinicians might be confronted with the prospect of treating multiple patients with wounds in a short time period, using equipment common to several patient treatments. In such a situation, any viable pathogenic microorganisms residing on ES equipment could potentially gain access to wounds.[21] These pathogens could hinder the healing process, detrimentally affect a patient's well being, or cause patient fatality.[22] Clinicians need to be aware of methods that reduce the risk from microbial pathogens, especially bacteria, while still providing wound treatment with ES.

Most disinfectants are chemicals, and they are generally used on inanimate objects or surfaces, rather than on living tissues.[23] Many chemical disinfectants are also called "germicides" because they are antimicrobial agents that kill living microorganisms and viruses, but not necessarily bacterial endospores. Endospores are dormant, resistant forms of certain bacteria.[24] They are resistant to heat and many chemical disinfectants, and they can remain dormant for long periods of time before germinating to produce the growing (vegetative) form than can cause infection. Disinfection is a process distinct from sterilization. Sterilization is a process that results in the complete removal of all microbial life from an object, including bacterial endospores and viruses.[23] Something that is sterile is free of any microbial life. Sterilization is most commonly accomplished through autoclaving or irradiation by x-rays or gamma rays, or with certain chemicals such as ethylene oxide.[23] Disinfectants tend to kill vegetative microorganisms or inhibit their growth, reducing the overall number of microorganisms (including pathogens) on an object or surface, but they do not usually sterilize an object or surface.[23]

The purpose of our study was to identify, practice, and refine an efficient, economical, practical, and safe method for disinfecting equipment common to all ES treatments within a multiple-patient, multiple-wound, and multiple-microorganism setting. Our protocol used materials and techniques that would ordinarily be found in any reasonably equipped clinical setting.

Materials and Methods

Electrical Stimulation and Disinfection

Electrical stimulation of all patient wounds in this study was performed using a Rich-Mar 2000 HVPC stimulator. Disposable face masks and sterile gloves were worn during ES and disinfection procedures to minimize possible contamination from the clinician/experimenter. Disinfection of all electrodes and electrode sponges was accomplished using Mikro-Quat[R] detergent/germicide/deodorizer.([dagger]) Mikro-Quat[R] contains 9.0% alkyl (50% [C.sub.14], 40% [C.sub.12], 10% [C.sub.10]) dimethyl benzyl ammonium chloride as its active ingredient.

Prior to the use of ES on any subject, the electrodes and electrode sponges were disinfected for 20 minutes by immersion in a plastic tub containing 18.6 g (Y3 OZ) of Mikro-Quat[R] diluted in 3.8 kg (1 gal) of water. After disinfection, the electrodes and sponges were removed from the tub using sterile gloves and then rinsed thoroughly for 5 minutes in tepid, running tap water. After rinsing, the electrodes were temporarily placed in a sterile field. The sponges were secured to the electrodes using sterile 10.2 x 10.2-cm (4 x 4-in) gauze soaked in 0.9% sterile saline. This served as a sterile barrier between the wound and the sponge surface on the electrode. Electrodes were temporarily placed in a sterile package until application (usually within 2-3 minutes). During this time, any dressings on the wound were removed, and the wound was lightly flushed with 0.9% sterile saline on sterile gauze to remove exudate and debris.

Following wound preparation, the treatment electrode was applied directly over the wound. The second electrode was placed on the immediate, opposite surface of the extremity. The electrodes were secured to the extremity via sterile dressing tape.+ After adjusting the settings on the ES apparatus, the time was set for 30 minutes and the intensity was slowly and gradually increased to a maximum of 150 V. Typical ES settings consisted of either negative or positive polarity (depending on repair interests) and a 120-pulse per second, 255-pulse paired-interval, continuous-current, nondispersive mode.

After 30 minutes of treatment, the ES apparatus was turned off, the electrodes and gauze were removed under aseptic conditions, and the wound was inspected. The sponges were removed from the electrodes, and the treatment sponge was disinfected in Mikro-Quat[R] as described previously.

Collection of Bacterial Samples

For the following procedures, a sterile rayon-tipped swab used was part of the BBL Culturette Collection and Transport System.([subsections]) The bacteriological medium used to culture all bacteria was blood-agar in 100-mm petri plates (blood-agar plates).([subsections]) Blood agar consists of tryptic soy agar plus 5% sheep blood.

Prior to the application of ES to each subject in this study, a sterile rayon-tipped swab was used to obtain a sampling of the bacterial flora present in the wound by carefully rubbing the swab across the wound surface. Following application of ES, another sterile rayon-tipped swab was used to obtain a sampling of the bacterial flora present in the wound in the manner just described.

In addition, prior to its use in ES on any subject in this study (but before the initial, pretreatment disinfection), a sampling of any bacterial flora present on an electrode sponge was obtained by blotting the sponge directly onto two blood-agar plates. After its use in ES on any subject in this study (but before the final, posttreatment disinfection), a sampling of any bacterial flora present on the electrode sponge was obtained by blotting the sponge directly onto two new blood-agar plates. After 20 minutes of posttreatment disinfection of any electrode sponge used for ES in this study, a sample of any bacterial flora present on the sponge was obtained by blotting the sponge directly onto two additional blood-agar plates. All rayon-tipped swabs and blood-agar plates were transported to the microbiology laboratory within 4 hours of sampling in the clinic.

Microbiology

Each rayon-tipped swab used to sample a pretreatment wound or a posttreatment wound was used to inoculate two separate blood-agar plates by the streak-plate method.[25](p630) One blood-agar plate from each of the five sampling situations described in the previous section was then incubated at 37[degree]C for 24 hours under aerobic conditions, and the other blood-agar plate from each of the five sampling situations was incubated for 72 hours under anaerobic conditions. Anaerobic conditions were obtained using an anaerobic jar culture system.[25](p342)([subsections]) Following incubation, any bacteria growing aerobically and anaerobically on these blood-agar plates were examined and characterized, and approximate or actual bacterial colony counts were made. A Gram staining was then performed on bacteria from each unique bacterial colony present on a blood-agar plate.[25](p46) In addition, bacteria from each unique colony were subjected to a catalase test.[25](p343) Further diagnostic tests were not routinely performed. The microbiological methods used in this study to characterize and quantify bacteria are standard techniques that are currently used and that have been used widely in both clinical and research microbiology laboratories for more than a century.[26]

To evaluate the effectiveness of a practical disinfection protocol utilizing a commonly available disinfectant to be used by physical therapists performing ES for wound management or for other purposes, we took samples of bacterial flora from the pretreatment wounds, the posttreatment wounds, the pretreatment electrode sponges (before initial, pretreatment disinfection), the posttreatment electrode sponges (before final, posttreatment disinfection), and the postdisinfected electrode sponges from 25 patient-treatment sessions, representing seven different patients (Tab. 1). The presence (or absence) of bacteria, their relative or actual numbers, and the types of bacteria recovered from each sample were determined by standard microbiological techniques [25](pp46,342,343,630) This procedure involved inoculating blood-agar petri plates with a particular sample (either from a swab or sponge), culturing the bacteria by incubating the blood-agar plates under either aerobic or anaerobic conditions at 37[degree]C for 24 to 72 hours, and then analyzing the resultant bacterial growth (if any) on these petri plates.

[TABULAR DATA 1 OMITTED] Any viable bacteria present at the sampled sites that were transferred to the blood-agar plates by either swabs or sponges were later visualized on this bacterial culture medium as bacterial colonies. A bacterial colony on a petri plate consists of millions or billions of microscopic bacterial cells growing together on top of each other to form a macroscopic, visible structure in the approximate shape of a dome.[25](p19) Each bacterial colony represents a clone of cells. A clone is a group of cells that all arose from a single, ancestral cell.(27) This means that each bacterial colony on a blood-agar plate represents the descendants of a single bacterial cell transferred to the petri plate during the initial inoculation by either a swab or a sponge. Thus, by determining the number of colonies on a petri plate, one is also determining the number of bacterial cells initially transferred there. If only a few bacterial cells are transferred, then these cells will form discrete colonies, each separated from the others. If many bacterial cells are transferred, then as they grow to form colonies, they tend to grow into each other, and discrete, countable colonies are unable to be observed. Instead, there is a general overgrowth of the petri plate surface consisting of hundreds or thousands of individual bacterial colonies growing into each other. Such a growth pattern is referred to as a "lawn" of bacteria.

Results

Results are presented in Tables 2 and 3. The data were then used to evaluate the efficacy of both the disinfectant and the disinfection protocol used.

[TABULAR DATA 2-4 OMITTED]

Typically, samples taken from the pretreatment and posttreatment wounds contained very large numbers of bacteria (Tabs. 2 and 3), often of several different species. An exact quantification of the number of bacteria in each wound was impossible. Individual species of bacteria from each wound sample, however, were identified as isolated, unique bacterial colonies. These colonies were produced by streaking out the initial swab inoculum with a sterile bacteriological loop. Unique bacterial species recovered from the wounds were then characterized in terms of their colony properties, Gramstaining properties (gram-positive or gram-negative), cellular morphology (spherical bacteria=cocci; rod-shaped bacteria=bacilli), and whether they were catalase-positive or catalase-negative. Large numbers of gram-positive cocci were recovered from all wounds. The great majority of these cocci were catalase-positive. In some patients, gram-negative bacilli, gram-positive bacilli, and pleomorphic (variable shape) gram-positive coccobacilli were also seen. In one patient, a filamentous fungi was observed. The identification of the pretreatment and posttreatment wound bacteria was useful for purposes of identifying the probable site of origin of any bacteria found on the posttreatment and postdisinfected blood-agar plates.

In contrast to the large numbers of bacteria recovered from the pretreatment and posttreatment wound samples, samples taken from the pretreatment electrode sponges (but before the initial disinfection) never yielded more than five bacterial colonies (Tabs. 2 and 3). The numbers of bacteria recovered from the posttreatment electrode sponges were variable, often depending on the particular patient. In some instances, no bacteria were recovered, whereas in other instances, one or more colonies were observed. In each of these cases, the types of bacteria recovered from the posttreatment sponge were the same as those identified from the patient's wound, indicating the transfer of bacteria from the wound surface to the electrode sponge surface.

The samples obtained taken from the posttreatment electrode sponges after they were disinfected never resulted in more than two bacterial colonies on a petri plate (Tabs. 2-4). For those samples cultured aerobically, the percentage of postdisinfectant sponge samplings containing no bacterial growth was 92% (23 out of 25 samples). The remaining 8% of postdisinfectant samples (2 out of 25 samples) contained two or fewer colonies. For those samples cultured anaerobically, the percentage of postdisinfectant sponge samples containing no bacterial growth was also 92% (23 out of 25 patient samples), and the percentage containing bacterial growth (two or fewer colonies) was again 8%.

Discussion

We evaluated the efficacy of a commonly available disinfectant and of a protocol for the disinfection of electrodes and electrode sponges used in ES. To our knowledge, no such study has yet been conducted. The approach we used involved sampling both the wounds and the electrode sponges prior to and after ES, and the electrode sponges after disinfection, for the presence and types of bacteria.

The disinfectant used in this study (Mikro-Quat[R]), belongs to a group of nontoxic (except at high concentrations) and widely used surfactant disinfectant/germicides called the quaternary ammonium compounds, or "quats.[28](p222) Surfactants, or surface active agents, are amphipathic chemicals (molecules with both hydrophilic and hydrophobic parts) that can penetrate oily substances in water and emulsify them (break oily substances into smaller droplets that form a fine suspension in water). Soaps and detergents are surfactants. Quaternary ammonium compounds are surfactant germicides that are cationic detergents (positively charged). Although their exact chemical mode of action is still unknown, quats most likely act by penetrating and destroying phospholipid membranes in cells, including the cell membrane of microbial cells, thereby changing the cells' permeability and causing the loss of essential cytoplasmic substances.[28](p222),[29] They kill all types of cellular microorganisms (bacteria, protozoa, fungi) and viruses that have membranes (enveloped viruses), although higher concentrations are required to kill gram-negative bacteria because of their protective outer membranes.[29] They do not, however, kill bacterial endospores or Mycobacterium tuberculosis, the causative agent of tuberculosis.[29]

The results of this study make it clear that the disinfectant used and disinfection protocol used are efficacious. Disinfection for 20 minutes (as described in the "Materials and Methods" section) is effective in reducing the number of bacteria on the electrodes and electrode sponges to safe, noninfective levels. In 23 of the 25 patient samples cultured aerobically and in 23 of the 25 patient samples cultured anaerobically, no bacteria were recovered on the blood-agar petri plates after disinfection, even though in most cases the posttreatment (but predisinfected) electrode sponges contained bacteria (Tabs. 2-4). This finding demonstrates that Mikor-Quat[R] effectively killed any bacteria transferred from the wounds to the sponge surfaces as a result of application of the sponges to the wounds during ES. In the remaining 2 patient samples cultured aerobically or anaerobically, no more than two bacterial colonies were recovered on the blood-agar plates. In both cases, each of these bacterial colonies represented the descendent cells of a single, original bacterial cell on the petri plate. There are two possible sources for these original bacterial cells. Either they were transferred from the wounds to the sponges and somehow escaped the germicidal effects of the disinfectant, or they were contaminants that were transmitted to the plates not from the patient wounds, but from some other source, such as one or more of the experimenters involved in this study, after disinfection of the sponges.

If the latter case is true, these bacteria pose no danger to the patient because they represent contaminating bacteria introduced to the blood-agar plates, and not to the sponges themselves. We believe that this is the most likely source of these bacterial colonies because they represent types of bacteria (staphylococci) found on the skins of the majority of people[28](p342) and are common contaminants found in many microbiological preparations. Even if the former case is true, however, we believe that the danger posed to the patient is still minimal because the actual number of bacteria on the sponges was so low. In the two aerobic cases and the two anaerobic cases where bacterial colonies were observed on the postdisinfected blood-agar plates, only one or two colonies were observed. These would represent one or two original bacterial cells transferred from the postdisinfected sponges to the blood-agar plates. This number is well below the number of bacteria that would usually be needed to overcome an individual's natural defenses and initiate a successful infection.[30] Besides, in the actual ES performed on each patient, there was a layer of sterile gauze between the electrode sponge surface and the patient's skin surface. If any viable bacteria were on the sponge after disinfection, if they were transferred at all, they would most likely be transferred to the surface of the gauze and not to the patient. As previously mentioned, however, we believe the source of these colonies on the postdisinfected sponges to most likely be the experimenters, rather than the patients' wounds.

The colonies observed on the pretreatment, preinitial disinfected sponges varied in number from zero to five. Although we did not sample the sponges for the presence of bacteria after they were initially disinfected but prior to their use in ES, we assume that any bacterial cells present on these sponges would have been killed by the 20 minutes of disinfection, based on the other disinfection data from this study. The presence of these colonies is possibly due to the nature of their storage between treatments in the facility in which this study was conducted. These sponges were stored in a less-than-ideal situation in two regards. First, they were not stored in a sterile manner. Second, they were stored in an area accessible to other clinicians and could have been used by these clinicians between our uses.

Conclusions

We believe that the data presented here strongly demonstrate that the disinfectant and the disinfection protocol used in this study are efficacious in reducing the risk of possible patient infection from ES equipment to minimal and acceptable levels. Such information may prove useful to infection-control personnel in nonhospital sites where ES is used or will be used and where access to autoclaves and other sterilants may not be readily available. The protocol presented here is also extremely cost-effective in that it utilizes a commonly available disinfectant and would permit the reuse of both electrodes and electrode sponges after disinfection within a reasonable time frame. Such a situation would prove extremely valuable in a multiple-patient treatment facility. Finally, the protocol and the disinfectant are safe. We did not observe adverse skin reactions, delays in healing, or damage to tissues in any of the seven patients involved in this study.

([double dagger])Duraspore Surgical Tape, 3M Health Care, St Paul-Minneapolis, MN 551441000. ([double dagger])Becton Dichnson (BBL) Microbiology Systems, PO Box 243, Cockeysville, MD 21030.

References

[1] Kloth LC. Physical modalities in wound management: WC, therapeutic heating and electrical stimulation. Ostomy/Wound Management. 1995;41:18-27. [2] Kloth LC. Electrical stimulation in tissue repair. In: McCulloch J, Kloth LC, Feedar JA, eds. Wound Healing: Alternatives in Management. 2nd ed. Philadelphia, Pa: FA Davis Co; 1995:275-317. [3] Akers, TK, Gabrielson, AL. The effect of high voltage galvanic stimulation on the rate of healing of decubitus ulcers. Biomed Sci Instrum. 1984;20:99. [4] Jaffe LF, Vanable JW. Electrical fields and wound healing. Clin Dermatol. 1984;2(3):34-44. [5] Carley PJ, Wainapel SF. Electrotherapy for acceleration of wound healing: low intensity direct current. Arch Phys Med Rehabil. 1985;66: 443-446. [6] Kloth LC, Feedar JA. Acceleration of wound healing with high voltage, monophasic, pulsed current. Phys Ther. 1988;68:503-508. [7] Gentzkow GD, Miller KH. Electrical stimulation for dermal wound healing. Clin Podiatr Med Surg. 1991;8:827-841. [8] Mulder GD. Treatment of open-skin wounds with electric stimulation. Arch Phys Med Rehabil. 1991:72:375-377. [9] Feedar JF, Kloth LC, Gentzkow GD. Chronic dermal ulcer healing enhanced with monophasic pulsed electrical stimulation. Phys Ther. 1991;71:639-647. [10] Gentzkow GD. Electrical stimulation to heal dermal wounds. J Dermatol Surg Oncol. 1993;19:753-758. [11] Hulsheger H, Potel J, Niemann KG. Killing of bacterial with electric pulses of high field strength. Radiat Environ Biophys. 1981;20:53-65. [12] Hulsheger H, Potel J, Niemann KG. Electric effects on bacteria and yeast cells. Radiat fat Environ Biophys. 1983 ;22: 149 -162. [13] Kincaid CB, Lavoi KH. Inhibition of bacterial growth in vitro following stimulation with high voltage, monophasic, pulsed current. Phys Ther. 1989;69:651-655. [14] Guffey GS, Asmussen MD. In vitro bactericidal effects of high voltage pulsed current versus direct current against Staphylococcus aureus. J Clin Electrophysiol. 1989;69:651-655. [15] McLaughlin S. The electrostatic properties of membranes. Annu Rev BiophysChem. 1989;18:113-136. [16] Szuminsky NJ, Albers AC, Unger P, Eddy JG. Effect of narrow, pulsed high voltages on bacterial viability. Phys Ther. 1994;74:660-667. [17] Laatsch LJ, Ong PC, Kloth LC. In vitro effects of two silver electrodes on select wound pathogens. J Clin Electrophysiol. 1995;7: 10 15. [18] Harkess N. Bacteriology. In: Mcculloch, Kloth LC, Feedar JA, eds. Wound Healing: Alternatives in Management. 2nd ed. Philadelphia, Pa: FA Davis Co; 1995:60-86. [19] Guidelines for the Treatment of Pressure. Rockville, Md: Agency for Health Care Policy and Research; 1995. [20] Jackson M, Lynch P. Infection control: in search of a rational approach. Am J Nurs. 1990;90(10):65-74. [21] Beck WC. How bacteria got from here to there: the basics of surgical asepsis. Infections in Surgery. 1985;4:266-267. [22] Mims CA, Playfair JHL, Roitt IM, et al. Medical Microbiology. St Louis, Mo: CV Mosby Co; 1993:16.1-16.14. [23] Martin MA, Wenzel RP. Sterilization, disinfection, and disposal of infectious wastes. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practices of Infectious Diseases. 4th ed. New York, NY: Churchill Livingstone Inc; 1995:2579-2587. [24] Russell AD- Bacterial spores and chemical sporicidal agents. Clin Microbiol Rev. 1990;3:99-119. [25] Brock TD, Madigan MT, Martinko JM, et al. Biology of Microorganisms. 7th ed. Englewood Cliffs, NJ: Prentice-Hall Inc; 1994:19, 46, 342, 343, 630. [26] Woods GL, Ayers LW, Washington JA. Medical bacteriology. In: Henry JB, ed. Clinical Diagnosis and Management 19 Laboratory Methods. 19th ed. Philadelphia, Pa: WB Saunders Co; 1996:1132-1169. [27] Atlas RM. Principles of Microbiology. St Louis, Mo: CV Mosby Co; 1995:54. [28] Ingraham JL, Ingraham CA. Introduction to Microbiology. Belmont, Calif: Wadsworth Inc; 1995:222, 342. [29] Petrocci AN. Surface-active agents: quaternary ammonium compounds. In: Block SS, ed. Disinfection, Sterilization, and Preservation. 3rd ed. Philadelphia, Pa: Lea & Febiger; 1983:309-329. [30] Murray PR, Kobayashi GS, Pfaller MA, Rosenthal KS. Medical Microbiology. St Louis, Mo: CV Mosby Co; 1994:111.

(*) Rich-Mar Corp, Rte 2, PO Box 879, Inola, OK 74036. ([dagger])Ecolab Inc, Ecolab Center, St Paul, MN 55102.

DP Kalinowski, PhD, is Assistant Professor of Biology, Department of Natural Sciences, Daemen College, 4380 Main St, Amherst, NY 14226 (USA) ([e-mail]). Address all correspondence to Dr Kalinowski.

MS Brogan, PT, is Assistant Professor of Physical Therapy, Department of Physical Therapy, Daemen College.

MD Sleeper, PT, is Assistant Professor of Physical Therapy, Department of Physical Therapy, Daemen College.

This article was submitted May 24, 1996, and was accepted August 13, 1996.