March 1, 2001
by Lauren Crawford, BS, Zhi-Jian Yu, Ph.D., Erin Keegan, BS, Tina Y
Some ideal characteristics of disinfectants used on environmental surfaces include rapid action in a broad antimicrobial spectrum, maintained efficacy in the presence of protein or blood, low toxicity, user safety, and material compatibility. Some disinfectants have limited use, because they do not meet all of these criteria. Table 1 shows a list of 10 disinfectants, the active ingredients, manufacturer, characteristics of the disinfectant, and a recommendation of the types of gloves that can be used with the product for up to one hour, (according to this study) which will be examined herein.
SPECTRUM AND RAPIDITY OF ANTIMICROBIAL ACTIVITY
The spectrum of the product refers to the range of recommended usage of the product, the sphere of microbial kill tested as well as the contact time and temperature, according to the manufacturer and the EPA-approved label. The ten products that are mentioned in Table 1 are similar in antimicrobial activity because they all claim to be bactericidal, fungicidal, and virucidal. However, not all disinfectants claim to be tuberculocidal. Envirosafe, Coverage HB, Coverage Spray, and Ascend are all low-level disinfectants, and they do not kill the tubercule bacillus (i.e. M. Bovis). Based on the disinfectant class, the range of antimicrobial activity is discussed in further detail below.
High concentration alcohol-based. Lysol I.C. Disinfectant Spray has a broad spectrum of antimicrobial activity with 79% ethyl alcohol has a recommended surface contact time of 10 minutes. High concentration alcohol products are generally not advocated for instrument immersion since the high alcohol content easily volatilizes, and thus diminishes antimicrobial activity. Additionally, alcohols can not be used as cleaners, which then requires the user to purchase a separate cleaner.
Chlorine-based. Dispatch can be used as a cleaner due to the presence of added surfactants and a deodorizer. It has a broad range of efficacy with a label claim contact time of 2 minutes at 20C. Both Babb and Alvarado et al. do not recommend chlorine-based compounds, such as the sodium hypochlorite contained in Dispatch, for disinfection of instruments and equipment.1,2 Robison et al. reported that a commercial disinfectant containing 0.55% sodium hypochlorite with a 2 minute contact time at room temperature displayed poor tuberculocidal activity.3 According to Robison’s study, the average time required for a 6-log10 reduction was in excess of 3 hours. However, the CDC recommends that 5.25% sodium hypochlorite (household bleach) diluted to a concentration of 0.05% can be used for the decontamination of a blood spill.4
Phenol-based. Wex-cide, ProSpray and Birex are germicidal, fungicidal, virucidal, and tuberculocidal in 10 minutes at 20C. Birex is a cleaner and deodorizer. Birex is not sold at the use-dilution, and therefore, diluting Birex involves an extra step. Surface disinfectants that require dilution can result in preparation errors, and incomplete disinfection due to an inappropriate disinfectant concentration.
Quaternary amine-based. Envirosafe, Coverage HB, Coverage Spray, and Ascend are all low-level quaternary amine-based disinfectants, and have a more prominently restricted efficacy range than the other products discussed herein. These product spectrums do not include tuberculocidal activity. With the exception of Coverage HB concentrate, they do not kill HBV (Hepatitis B Virus). Additionally, Envirosafe, Coverage HB, and Ascend are not sold at the optimum concentration, and dilution is required. Envirosafe, Coverage HB, Coverage Spray, and Ascend can be used for ultrasonic cleaning, and as general cleaners. The four quaternary amine products can also be used for (limited) instrument immersion for the allotted time to kill microorganisms. However, surface disinfectants in general are not recommended as permanent holding solutions.
Quaternary amine/low concentration alcohol-based. The synergistic mechanism of quaternary amines in the presence of alcohols involves the breakdown of the lipoprotein complexes by the quaternary amines in the cell membrane of microorganisms.5 The opening of the membrane thereby allows the alcohol, which is a protein denaturant, to penetrate the cell membrane and cause irreversible damage inside the cell.6 Cavicide has a broad spectrum of antimicrobial activity with a recommended surface contact time of 10 minutes at 20C. It can be used as a cleaner, as an ultrasonic cleaning solution, and for instrument immersion.
Resistance to organics (soils)
Including blood in all active ingredient efficacy testing is important because clinicians rarely deal with pure cultures of microorganisms. Clinically, microorganisms are usually contained within proteinaceous material such as blood, plaque, saliva, etc. Inclusion of these proteins in tests is important since these proteins interfere with the antimicrobial activity of disinfectants. For this reason, it is a good clinical practice, and a mandated labeling requirement from the EPA to clean surfaces of gross debris prior to disinfection.
MATERIAL AND INSTRUMENT COMPATIBILITY
High concentration alcohol-based. The ideal surface disinfectant produces negligible changes in appearance or function of medical devices and surfaces with which it comes into contact. It is non-corrosive to metals, adhesives, plastics, gloves, etc. Prolonged exposure to alcohol has been known to disrupt adhesives, damage seals, cause certain plastics to swell and harden, which could make them more brittle and prone to break.7
One of the most damaging disinfectants is sodium hypochlorite. Dispatch is not recommended for use on aluminum surfaces.8 A 0.53% solution of sodium hypochlorite caused significant corrosion of a Schiotz tonometer including the metal components just after 24 hours of soaking, and significant damage was seen after 11 days of soaking.9 Another study on acupuncture needle sterilization with 5.25% sodium hypochlorite showed that the solution completely dissolved the needle after 30 minutes of exposure.10 The pH of Dispatch is at 12.2, which may further contribute to the corrosive activity of sodium hypo chlorite, particularly to soft metals such as brass as well as to rubber and polyurethane.11
Phenol-based. Phenolic compounds are more difficult to rinse from equipment than other disinfectants. Kahn12 reported that equipment and devices treated with phenols, particularly para-tertiary amyl phenol, caused depigmentation of the skin and injury to mucous membranes. In figure 1 shown below is a photograph of stained gloves after soaking in Birex solution (containing approximately 300 ppm each of o-phenylphenol and p-tertiary amyl phenol) at use dilution.
GLOVE COMPATIBILITY STUDY RESULTS
Glove compatibility is a critical factor to consider when selecting a surface disinfectant. Gloves are one of the most important means of personal protective equipment. Undetected glove permeation poses infection and toxicity risks for clinicians. Gloves can fail without the knowledge of the user, whether by cuts, pinholes or permeation. It is important that the proper type and quality (e.g., thickness) of glove be worn when working with disinfectants.
The permeation of disinfectants through gloves can be indicative of the skin exposure to bloodborne pathogens as some chemicals degrade or even increase permeability of the glove material. Table 2 displays more detailed information about the gloves that were used in this compatibility study.
Glove permeation was tested according to the American Society of Testing and Materials (ASTM) method F739.13 The three glove types were exposed to each disinfectant for approximately 6 hours. The active components in each disinfectant (as mentioned in Table 1), for which standardized methods exist, were detected using an HPLC, with the exception of Envirosafe. For Envirosafe, a UV detectable chemical was added to facilitate the detection with the HPLC, and controls were also performed where the detectable chemical was mixed with deionized water and checked for permeation. The results are presented in Table 3.
The breakthrough time is the time required for the liquid to be transported through the glove and be detected by the HPLC, and represents the potential usable time. No skin exposure occurs if the glove is removed prior to the breakthrough detection time. Nitrile gloves of 0.011 cm thickness can resist permeation for longer than 5 hours for all except 2 products including Ascend, and Coverage HB Concentrate. Latex and PVC gloves did not perform as well as nitrile. PVC gloves of 0.017 cm thickness persisted permeation for longer than 5 hours for Lysol I.C. Spray, Cavicide, and Envirosafe. The PVC gloves provided less than 18 minutes of protection from ProSpray, Coverage HB Concentrate, Coverage Spray, and Ascend. Powdered latex of 0.011 cm thickness lasted for over 5 hours for four products including Lysol I.C. Spray, CaviCide, Coverage HB Concentrate and Envirosafe. The powdered latex lasted less than 18 minutes for ProSpray (< 10 minutes), Birex (15 minutes), Coverage Spray (< 13 minutes), and Ascend (18 minutes).
Since latex is one of the more commonly used types of gloves, the tear strength was tested to determine the force per unit required to pull the glove apart. After 6 hours of soaking at 30C in each disinfectant, the tear test was measured using an automated machine, the Instron model 4467. The tests were performed according to the ASTM method D624 on the same powdered latex gloves that were tested for permeation above.14 Four glove specimens per disinfectant were cut and tested using the Die C shape, as described in the method. The glove samples were soaked in deionized water as a negative control, emulating the best-case scenario, and in mineral oil, which is known to deteriorate latex for the positive control. Results are presented in Figure 2. The values shown represent the tear test values after normalizing by setting water equal to 1.
From the figure, it can be seen that other than water, ProSpray performed the best, followed by Dispatch, Cavicide and Envirosafe. The product formulations that appear to most alter the tear strength of powdered latex gloves include Birex, Coverage Spray, and Wex-Cide.
Since various brands of the same generic latex material may have different permeation and physical properties for the same liquid, the selection of chemical protective gloves would ideally be based on specific permeation or tear strength data. However, the disparate breakthrough detection times for each category of disinfectant indicates that generalizations based upon the permeation characteristics of the individual components in the mixture is not ideal. In other words, the permeation and tear strength seems to be specific to the entire product, rather than being based upon the broad class of disinfectant alone (e.g. phenol-, or chlorine-based, etc.).
All chemical substances will eventually permeate gloves given enough time, and therefore the toxicity of the surface disinfectant should also be considered. The following descriptions discuss toxicity based upon the category of disinfectant being evaluated.
Ethanol – Based. Ethanol can increase the volume of the polar pathway of the skin, thereby creating new pores, or expand the existing ones that result in increased permeability of the strateum corneum layer (15). Thus, ethanol-based products may be suspect to problems wherein the ethanol expands the pores allowing bacteria or dangerous chemicals to seep into the skin. Additionally, ethanol can dry the skin. Appropriate gloves should be worn and changed frequently enough to inhibit harmful chemicals or bacteria from penetrating into the skin via an ethanol medium.
Chlorine – Based. In 1994, the Clinton Administration announced a Clean Water Plan that could eventually eliminate chlorine and chlorine-based products due to the many hazards they entail. Sodium hypochlorite is an oxidizer that has been implicated in many household accidents and/or deaths, according to the American Association of Poison Control Center’s annual reports.16 Additionally, special hazards exist when using sodium hypochlorite on surfaces previously treated with other germicides. Improper use may result in cross-contamination with acid-containing products such as toilet bowl cleaners, or ammonia to create dangerous or fatal by-products.17 Furthermore, concentrations of sodium hypochlorite as small as 0.04% have been shown to elicit positive skin contact sensitivity responses in a clinically sensitized individual.18
Phenol – Based. In 1994, the OEHHA (Office of Environmental Heath Hazard Association), which is a division of the U.S. EPA, classified ortho-phenylphenol (OPP) as a carcinogen, and many studies have shown the cytotoxicity and genotoxicity of OPP.19-23 OPP has been labeled by the EEC with risk phrase R36/38, indicating that it is irritating to the skin and eyes.24 There have been reported cases of allergic contact dermatitis, contact urticaria (hives) or of depigmentation of the skin.25,12 The phenol-based residue contamination on non-critical items after using a surface disinfectant can cause hazardous injury to tissue or mucous membranes with which they contact.26 Moreover, phenol-based products are limited in that they can not be used in the proximity of neonatal areas, particularly isolettes, or other infant contact surfaces.
Quaternary Amine or Quaternary Amine / low concentration alcohol-based. Quaternary amines such as benzalkonium chloride and benzethonium chloride are commonly used in small concentrations in after-dinner skin wipes, skin disinfectants as well as in ophthalmic, cosmetic and food preservatives. Alfredson et al. demonstrated that alkyldimethylbenzyl ammonium chloride (benzalkonium chloride) at 0.25% in the diet of rats over a 2-year feeding period did not demonstrably affect the treated animals.27 The final report on the safety assessment of benzethonium chloride (diisobutylphenoxyethoxyethyl dimethylbenzyl ammonium chloride) and benzalkonium chloride has been issued by the CTFA (Cosmetic, Toiletry and Fragrance Association) and concluded that the compound is safe at concentrations of 0.5% and below in cosmetics applied to the skin, and safe at 0.02% for cosmetics used in the eye area.28 The quaternary amine products including Envirosafe, Coverage HB Concentrate, and Ascend are therefore safe at the use dilution. Cavicide and Coverage Spray are also safe if exposed to the skin since the quaternary amine levels are below the CTFA guidelines. Although quaternary amines are not as toxic as the previously mentioned active components, the glove pores may still be opened by the product components to allow permeation of bacteria. As with all cleaners and disinfectants, proper personal protective equipment and universal precaution is recommended.
Significant differences exist between the ten surface disinfectants examined including antimicrobial activity, toxicity, instrument corrosion and material and glove compatibility. The maintenance of a good barrier function of gloves requires regular changing, and the proper selection of glove material for the surface disinfectant being used. “Universal precautions” such as changing gloves after each patient contact and good handwashing after using gloves should be carefully observed. No-touch techniques and choosing the right glove for the particular surface disinfectant decrease the possibility of microorganisms in blood or toxic chemical contact during surface disinfection.
Ideal surface disinfectants for infection control in the healthcare environment requires delivery of a consistently rapid, broad-spectrum kill of resistant microorganisms accompanied by heavy protein, while minimizing toxicity to the user. OH
Lauren Crawford, B.S. is a Research Chemist with over 3 years infection control experience at Sybron Dental Specialties. Zhi-Jian Yu, Ph.D. is a Senior Scientist at SDS who is a surface science expert with over 25 publications in top surface science journals and over 5 years industrial experience in infection control. Tina Yu, M.S. is a Research Chemist at SDS. Erin Keegan, B.S. is a technical representative at SDS that oversees the correct use of infection control products.
Oral Health welcomes this original article. References available upon request.
Research scientists and investigators from manufacturers and investigators in the private sector often present interesting and important information. While this article refers to some products that are not easily available in Canada, the description of various categories of disinfectants would help one chose a representative product in this country.
R. A. Clappison, DDS, FRCD(C)
Table 1: Summary of disinfectants and glove compatibility (refer to the body of paper for specific information and criteria)
Legend: * = acceptable, X = unacceptable
Table 2: Glove material, manufacturer, cost/glove and average thickness.
Table 3: Glove permeation of surface disinfectants with three different types of gloves.
Breakthrough Detection Time is the time at which the permeation reached 0.25 ug/cm2
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