I’ve been asked to write a chapter providing an overview of options for antimicrobial surfaces in hospitals for a Springer book. As a result of the preliminary literature reviews for this chapter, I’ve summarized the various available options for antimicrobial surfaces in hospitals in this post.
A number of different interventions aimed at improving environmental hygiene have been evaluated. Switching from one disinfectant to a product with superior microbiological efficacy in particular has been shown to reduce transmission.1-6 However, one of the problems with available disinfectants is the lack of residual effect, meaning that recontamination occurs quickly.7,8 An attractive option is to somehow make surfaces antimicrobial to exert a continuous reduction in the level of contamination. A recent review by Prof Hilary Humphreys provides a useful overview of the various approaches to antimicrobial surfaces.9 There are several approaches to making a hospital surface ‘antimicrobial’:
- Permanently ‘manufacture in’ an agent with antimicrobial activity (e.g. copper or a chemical).
- Periodically apply an agent with antimicrobial activity (e.g. copper containing liquid agents, or chemical disinfectants with residual activity).
- Physically alter the properties of a surfaces to make it less able to support microbial contamination or easier to clean (e.g. antibiofilm surfaces).
The table below provides an overview of the various options available to make a hospital surface antimicrobial.
| Candidate | Application | Pros | Cons |
| Metals | |||
| Copper | Manufactured in / liquid disinfectant | Rapidly microbicidal; large evidence-base; evidence of reduced acquisition. | Sporicidal activity equivocal; cost, acceptability and durability may be questionable. |
| Silver | Manufactured in / liquid disinfectant | Broadly microbicidal. | ? sporicidal; tolerance development; relies on leaching so surface loses efficacy over time. |
| Chemicals | |||
| Organosilane | Liquid disinfectant | Easy to apply. | Limited microbicidal activity; questionable “real-world” efficacy. |
| Light-activated (e.g. titanium dioxide or photosensitisers) | Manufactured in / liquid disinfectant | Broadly microbicidal; can be activated by natural light. | ? sporicidal; requires light source for photoactivation (some require UV light); may lose activity over time. |
| Quaternary ammonium compound based | Liquid disinfectant | Easy to apply. | Limited microbicidal activity; largely untested real-world activity. |
| Triclosan | Manufactured-in / liquid disinfectant | Already adopted in some consumer markets. | Resistance / tolerance development; relies on leaching so surface loses efficacy over time. |
| Polycationic e.g. polyhexamethylene biguanide, PHMB | Liquid disinfectant | Easy to apply. | Limited microbicidal activity; questionable “real-world” efficacy. |
| Physical alteration of surface properties | |||
| “Liquid glass” (silicon dioxide) | Liquid application | Reduces deposition; improves ‘cleanability’. | Not microbicidal; some evidence of reduced contamination; unknown required frequency of application. |
| Sharklet pattern | Manufactured-in | Reduces deposition; reduced. biofilms. | Not microbicidal; not feasible to retrofit. |
| Advanced polymer coatings (e.g. polyethylene glycol PEG, superhydrophobic/philic, zwitterionic) | Manufactured-in | Reduces deposition; some can be ‘doped’ with copper or silver. | Not microbicidal; may be expensive; scale up to large surfaces questionable; not feasible to retrofit. |
| Diamond-like carbon (DLC) films | Manufactured-in | Reduces deposition; can be ‘doped’ with copper or silver. | Not microbicidal; likely to be expensive; feasibility of scale up to large surfaces questionable; not feasible to retrofit. |
There are some other options not listed in the table, that could be considered candidates for antimicrobial surfaces, although they are currently at an early stage of development, including:
- Negative air ionization to repel bacteria from surfaces.10
- Enzymes immobilized on surfaces.11
- Bacteriophages immobilized on surfaces.12
There is an impressive and rapidly emerging evidence-base for copper surfaces.13 The implementation of copper high-touch surfaces, which have a continuous biocidal action, results in a reduction in contamination and may reduce transmission.14-16 However, copper is expensive, difficult to retrofit and durability may be questionable.13,17 Thus, an effective disinfectant with a residual activity that does not compromise staff or patient safety or promote the development of reduced susceptibility is desirable. Several candidate disinfectants that have residual activity with a variety of active chemicals have emerged.18-22 These can be delivered through pre-existing cleaning and disinfection arrangements at little or no extra cost. However, there is very little published data on the microbiological or clinical impact of disinfectants with residual activity. A number of recent study suggest that promising in vitro activity may not translate into “real-world” impact: a recent study by Boyce et al. found that two organosilane products simply did not work as intended when applied to surfaces in a US hospital.22
During my research for this post, I came across a very useful presentation by Peter Hoffman from Public Health England, which can be downloaded here. Taking some of his ideas, plus a few of my own, the following points for discussion emerge:
- Which is the optimal deployment mode – antimicrobial agents that are manufactured in or periodically applied, or ways to make the surface physically less able to support contamination or easier to clean?
- If periodic application is selected, how frequently is a fresh application required (i.e. how durable is the antimicrobial coating)?
- Which surfaces should be made antimicrobial? It’s probably not feasible to do them all, particular for antimicrobial options that need to be manufactured in.
- Surfaces in hospitals are often dirty (obviously); it’s not clear how much the presence of organic matter would interfere with the activity of antimicrobial surfaces. Clearly, antimicrobial surfaces do not obviate the need for careful attention to hospital cleaning and disinfection. In fact, their continued effectiveness depends on it.
- The deposition of contamination and potential acquisition of contamination through contact with surfaces often occurs in quick succession, so antimicrobial surfaces with a contact time measure in minutes (rather than seconds) may be too slow to be useful.
- C. difficile spores represent a real challenge to antimicrobial surfaces. Copper seems to get closest to demonstrating inactivation, but even here data are somewhat equivocal.23 Could introducing an antimicrobial surface that is not effective against C. difficile “squeeze the balloon” and provide a selective advantage to C. difficile?
- How effective will antimicrobial surfaces that rely on an active agent leaching from surfaces be in a dry environment?
- How do we test – and compare efficacy – of antimicrobial surfaces? A standardized test has been proposed,24 but not yet adopted widely. Importantly, this methodology specifies an aerosol deposition of microbes whereas other proposed methodologies specify the deposition of microbes in a liquid suspension. Testing the ‘wet’ deposition of microbes may overestimate the antimicrobial potential of the surfaces, which would usually be challenged with dry deposition in the real world.
- Much of the literature for antimicrobial surfaces is published in materials science journals, as illustrated in this useful review by Page et al.25 I, for one, find this pretty difficult to access; as a healthcare scientist, it’s a new and daunting language to learn.
- The cost, and cost-effectiveness of implementing antimicrobial surfaces in the healthcare setting has not been rigorously assessed.
There’s a plethora of potential options and approaches to make a hospital surface ‘antimicrobial’. Copper is leading the way as a candidate, although other options are available. Making a surface less able to support contamination in the first place, and / or easier to clean is another tempting option, particularly if this can be combined with a level of antimicrobial activity. Finding and evaluating the optimal antimicrobial surface will require a multidisciplinary approach, requiring industrial partners, materials scientists, healthcare scientists and epidemiologists to refine and test the available options. More studies in the clinical setting, ultimately including those with a clinical outcome, are required.
Photo credit: Benjamin Hall.
References
1. Mayfield JL, Leet T, Miller J, Mundy LM. Environmental control to reduce transmission of Clostridium difficile. Clin Infect Dis 2000; 31: 995-1000.
2. Donskey CJ. Does improving surface cleaning and disinfection reduce health care-associated infections? Am J Infect Control 2013; 41: S12-19.
3. McMullen KM, Zack J, Coopersmith CM, Kollef M, Dubberke E, Warren DK. Use of hypochlorite solution to decrease rates of Clostridium difficile-associated diarrhea. Infection Control and Hospital Epidemiology 2007; 28: 205-207.
4. Boyce JM, Havill NL, Otter JA et al. Impact of hydrogen peroxide vapor room decontamination on Clostridium difficile environmental contamination and transmission in a healthcare setting. Infect Control Hosp Epidemiol 2008; 29: 723-729.
5. Orenstein R, Aronhalt KC, McManus JE, Jr., Fedraw LA. A targeted strategy to wipe out Clostridium difficile. Infect Control Hosp Epidemiol 2011; 32: 1137-1139.
6. Hayden MK, Bonten MJ, Blom DW, Lyle EA, van de Vijver DA, Weinstein RA. Reduction in acquisition of vancomycin-resistant enterococcus after enforcement of routine environmental cleaning measures. Clin Infect Dis 2006; 42: 1552-1560.
7. Hardy KJ, Gossain S, Henderson N et al. Rapid recontamination with MRSA of the environment of an intensive care unit after decontamination with hydrogen peroxide vapour. J Hosp Infect 2007; 66: 360-368.
8. Otter JA, Cummins M, Ahmad F, van Tonder C, Drabu YJ. Assessing the biological efficacy and rate of recontamination following hydrogen peroxide vapour decontamination. J Hosp Infect 2007; 67: 182-188.
9. Humphreys H. Self-disinfecting and Microbiocide-Impregnated Surfaces and Fabrics: What Potential in Interrupting the Spread of Healthcare-Associated Infection? Clin Infect Dis 2013;
10. Shepherd SJ, Beggs CB, Smith CF, Kerr KG, Noakes CJ, Sleigh PA. Effect of negative air ions on the potential for bacterial contamination of plastic medical equipment. BMC Infect Dis 2010; 10: 92.
11. Pangule RC, Brooks SJ, Dinu CZ et al. Antistaphylococcal nanocomposite films based on enzyme-nanotube conjugates. ACS Nano 2010; 4: 3993-4000.
12. Markoishvili K, Tsitlanadze G, Katsarava R, Morris JG, Jr., Sulakvelidze A. A novel sustained-release matrix based on biodegradable poly(ester amide)s and impregnated with bacteriophages and an antibiotic shows promise in management of infected venous stasis ulcers and other poorly healing wounds. Int J Dermatol 2002; 41: 453-458.
13. O’Gorman J, Humphreys H. Application of copper to prevent and control infection. Where are we now? J Hosp Infect 2012; 81: 217-223.
14. Salgado CD, Sepkowitz KA, John JF et al. Copper surfaces reduce the rate of healthcare-acquired infections in the intensive care unit. Infect Control Hosp Epidemiol 2013; 34: 479-486.
15. Schmidt MG, Attaway HH, Sharpe PA et al. Sustained reduction of microbial burden on common hospital surfaces through introduction of copper. J Clin Microbiol 2012; 50: 2217-2223.
16. Rai S, Hirsch BE, Attaway HH et al. Evaluation of the antimicrobial properties of copper surfaces in an outpatient infectious disease practice. Infect Control Hosp Epidemiol 2012; 33: 200-201.
17. Weber DJ, Rutala WA. Self-disinfecting surfaces. Infect Control Hosp Epidemiol 2012; 33: 10-13.
18. Keward J. Disinfectants in health care: finding an alternative to chlorine dioxide. Br J Nurs 2013; 22: 926, 928-932.
19. Hedin G, Rynback J, Lore B. Reduction of bacterial surface contamination in the hospital environment by application of a new product with persistent effect. J Hosp Infect 2010; 75: 112-115.
20. Baxa D, Shetron-Rama L, Golembieski M et al. In vitro evaluation of a novel process for reducing bacterial contamination of environmental surfaces. Am J Infect Control 2011; 39: 483-487.
21. Brady MJ, Lisay CM, Yurkovetskiy AV, Sawan SP. Persistent silver disinfectant for the environmental control of pathogenic bacteria. Am J Infect Control 2003; 31: 208-214.
22. Boyce JM, Havill NL, Guercia KA, Schweon SJ, Moore BA. Evaluation of two organosilane products for sustained antimicrobial activity on high-touch surfaces in patient rooms. Am J Infect Control 2014;
23. Wheeldon LJ, Worthington T, Lambert PA, Hilton AC, Lowden CJ, Elliott TS. Antimicrobial efficacy of copper surfaces against spores and vegetative cells of Clostridium difficile: the germination theory. J Antimicrob Chemother 2008; 62: 522-525.
24. Ojeil M, Jermann C, Holah J, Denyer SP, Maillard JY. Evaluation of new in vitro efficacy test for antimicrobial surface activity reflecting UK hospital conditions. J Hosp Infect 2013; 85: 274-281.
25. Page K, Wilson M, Parkin IP. Antimicrobial surfaces and their potential in reducing the role of the inanimate environment in the incidence of hospital-acquired infections J Mat Chem 2009; 19: 3819-3831.
Reflections on Infection Prevention and Control 
Great write-up, Dr. Otter! The chapter will be greatly used. Are you only considering hard, non-porous surfaces? As a long time industrial hygienist and occupational health researcher, I see environmental surfaces as including items in healthcare settings that healthcare workers, patients, and their families come into regular contact with to include environmental surfaces that can be fixed (chairs, couches, etc.), portable (sheets, privacy curtains, cuffs, etc.), and mobile (scrubs, lab coats, apparel, etc.). These surfaces are often porous by nature because they are fabrics, upholstery, and textiles.
Your list above of antimicrobial agents includes these types of surfaces that can now be treated as well. It will be increasingly important to build an evidence-base so that the healthcare community can determine what is best and safest for them as they explore textiles and fabric fibers that can be embedded with either leaching or non-leaching antimicrobial technologies. Also to consider is if the antimicrobial alone is appropriate for the level of bioburden that can be expected (vomit, feces, blood, urine) or if there is a need to explore properties beyond antimicrobial alone to include properties like fluid-repellency (this property is offered de-facto by the materials used in nonporous surfaces, they are by hydrophobic).
Portable or mobile porous surfaces tend to translate into broader exposure potential as they move around the hospital and traditional high touch, environmental surfaces like sink countertops and light switches do not. Given the latest paper on the incorrect use of clinical gloves, it is clear that hand hygiene is not enough paired with environmental decontam and that more is needed http://www.sciencedirect.com/science/article/pii/S0195670113003812
There are a long list of publications I can send to you. Given SHEA Guidance on Healthcare Apparel here in the U.S., this is a perfect time to expand this issue into a brighter global spotlight. http://www.jstor.org/stable/info/10.1086/675066 — Dr Bearman’s original paper is here — http://www.ncbi.nlm.nih.gov/pubmed/22314064 — Also a great paper out of the UK about home laundering of uniforms — http://www.ifh-homehygiene.org/best-practice-review/infection-risks-associated-clothing-and-household-linens-home-and-everyday-life — and finally a paper that needs more visibility from these incredibly intuitive Slovenian researchers — http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3499872/
Your work is outstanding, your impact noticeable, and your fan base ever growing. Keep it up, we depend on you.
A Mitchell, DrPH, MPH, CPH
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Thank-you Amber for this very useful comment. I have decided to restrict the review to hard surfaces, and leave fabrics and soft furnishing to another day. It’s worth noting that Prof Humphreys included a short section on antimicrobial fabrics in his review: http://www.ncbi.nlm.nih.gov/pubmed/24265359.
I agree that many if not most of the candidates for antimicrobial hard surfaces are also viable candidates for fabrics and soft furnishings.
I also agree that a combination of improved cleanability with antimicrobial activity is the optimal candidate. It may be that several of the advanced polymer coatings will deliver this in the near future.
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Great article I am looking forward to the discussion. After 17 years in this industry, with a specific focus on surfaces, I am writing a book “Surfaces Are the Bottom Line” due to be completed in June 2014.
The issue of surfaces is very complicated. The solution is not just find an antimicrobial surface that is “effective”. Nor is it just finding yet another effective disinfection product. Like everything the solution is a combination of these. However it starts with an entirely different evaluation of surfaces.
I will present some of these in my talk at the APIC National conference June 7th in Anaheim.
In a recent blog post Sally Bloomfield asked about the definition of “clean”. I would ask the same question about antimicrobial surfaces, which is used fairly loosely. Define an “antimicrobial surface”. Please realize there are people who believe an antimicrobial surface cleans itself,therefore does not need to be cleaned.
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Superb Thank you……
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Plastic profiles that have antimicrobial characteristics will prevent the transfer of microbes from the environment to people. This is because of their amazing characteristics. They are made up of compounds that make it impossible for bacteria and fungi to survive on the surface.
Markets that need antimicrobial profiles
A number of markets can benefit from these products. First and foremost, they are highly demanded by food manufacturers. Also, there are needed by market players in the field of medicine, construction and aerospace.
The popularity of antimicrobial plastic extrusions is increasing with every passing day. This is due to the need for safety.
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Jon
I read your blog which I like. I have a question for you about antimicrobials have you test of seen results on “SaniKleen®-ResiDX™ is a 5% active 3-(trihydroxysilyl) propyldimethyloctadecyl ammonium chloride in a stabilized aqueous solution”
I would really like to hear what you have to say.
Thanks
Mike
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Mike, this is an organosilane product, which is EPA-registered. The EPA registration number is 10324-197-58300, but not sure whether this relates to the new EPA test for residual activity on hard, dry surfaces http://www.epa.gov/oppad001/cloroxpcol_final.pdf.
The in vitro activity looks interesting, but the in situ activity may be questionable due limitations in achieving a durable application based on this study, which is the only peer reviewed published study of organosilane products with a healthcare application to my knowledge: http://www.ncbi.nlm.nih.gov/pubmed/24406256.
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I am also very interested in the organosilane product described above, we have formulated this product in an aqueous solution containing additional quats, the combination of the formulation is very powerful. The product has passed the EPA residual self sanitisation test under GLP . In summary the product was sprayed onto a surface which subsequently undergoes 12 wipes (dry and wet) and 5 re inoculations before undergoing the final test.
It would be useful to know what data would be required to satisfy the need for ‘real world efficacy’ in a report like this. We would really like to prove the benefits of this formulation but struggle because there is limited acceptance of the efficacy of quats and organosilanes and often the novelty is in the formulation.
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Dr Rogers, it’s good to know that the product has passed the EPA test for residual activity. That’s impressive, and you should try to get it published in a peer-reviewed journal.
The EPA test can never satisfy the need for a real-world assessment of the product; it’s an in vitro laboratory test. The product needs to be applied to some surfaces in the real hospital environment with others used as a control, with repeated environmental sampling used to compare impact. The methodology used in the Boyce study is sound (apparently, apart from the actual application of the organosilane): http://www.ncbi.nlm.nih.gov/pubmed/24406256. You will need to collaborate with a hospital to do this.
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Jon,
For antimicrobial purpose, copper could take the action in several different states, such as metal copper sheet, copper particles (micro-, nano-), copper carbonate powder, copper sulfate solution, etc.
I have been working on the development of copper-based mineral antimicrobial additive. We used selected natural minerals as a host material of ionic copper to produce antimicrobial mineral additives, then blend the additives into plastics, paints, etc. to form copper-based antimicrobial touch surface. This approach is totally different from copper metal sheet: (1) ionic copper is more efficient than metal copper; (2) copper ions released from the host minerals is very slow and adjustable, which increase the antimicrobial durability of the surfaces; (3) can reduce unit consumption of copper in the product which lower the cost; (4) broaden the surfaces to be treated (plastics, paints, rubbers,wood products, papers, etc.). Please refer to http://www.surfion.com for more details.
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A new none toxic, long lasting, cost effective surface broad spectrum biocide has proven effective in several applications, including hospital O.R. suites. The silver citrate – titanium oxide water based formula is applied after normal hygiene cleaning with a proprietary high pressure, electrostatic fog producing apparatus. Post application ATP testing has demonstrated colony forming unit (CFU) counts have dropped from 2,000 cfu’s to under 400 cfu’s within 30 minutes and continue the reduction for several days after application. Unlike other disinfecting agents containing chlorine, hydrogen peroxide, formaldehyde or alcohol, the Nano Nano Sterisol is none toxic, non flammable, non-corrosive and not a carcinogen. Safe for exotic O.R. electronics,post application re-occupancy is within 15 minutes. The electrostatic application creates magnetic-like properties to the nano particles, permitting penetration into minute surface irregularities, impossible with typical hand ap plied ‘cleaning’ practice. Cost is in the range of $0.07 per cubic foot with normal illumination UV photo -catalytic activation lasting over three months.
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Thanks Fred, but how did ‘post application ATP testing demonstrated that CFU counts dropped’. ATP does not measure CFU counts! The cost sounds reasonable, but excitation with UV will be challenging.
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I have read the article by Jon Otter. Very good article. Over my head in some ways . I look at this issue from a different perspective. My company manufactures countertops. The biggest challenge I see is not in treating the surface with a chemical, but in eliminating cracks where bacteria etc. can hide from cleaning and cleaning agents. In countertops this primarily occurs when the backsplash meets the deck. In a majority of specs it seems that the economical field applied splash leaves a considerable gap for bacteria, viruses etc. No amount of antibacterial treatment will provide a fail safe if there are cracks and gaps. Cove backsplashes and endsplashes in either laminate or solid surface are a more cost-effective solution the keeping these surfaces clean. These are both non-porous and easy to clean materials. They both cost more upfront, but payoff over time. If anti-microbial treatments can be added to these types of products then true gains would be made in keeping health facilities clean.
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