Modern technologies for improving cleaning and disinfection of environmental surfaces in hospitals

Multiple studies have shown that manual cleaning and disinfection of surfaces in hospitals is suboptimal. In many facilities, only 40 to 50 % of surfaces that should be cleaned are wiped by housekeepers [5]. In addition, observational methods combined with use of adenosine triphosphate (ATP) bioluminescence have shown that individual housekeeper performance varies considerably [6]. One study found variations among housekeepers in the amount of time spent cleaning surfaces, the number of wipes used in each room, and the level of cleanliness achieved [6]. Specialized cleaning teams that included infection control personnel have been shown to reduce C. difficile surface contamination more effectively than routine housekeepers [7]. Personnel turnover among Environmental Services departments is a significant problem [8, 9], which may reach 30 to 50 % in some facilities. As a result, shortages in Environmental Services personnel were reported by more than 50 % of hospitals in a recent survey conducted in the United States [10]. Among housekeepers and nursing personnel, there is often confusion about who is responsible for cleaning various surfaces and equipment [11, 12].

In addition to the above personnel-related issues, there are many other factors that can potentially have adverse effects on the efficacy of traditional cleaning and disinfection practices. The type of surface being cleaned or disinfected can affect the completeness with which bacteria are removed. For example, Ali et al. found that the type of material from which bed rails were made affected how well they could be cleaned by microfiber cloths, and that bacteria were removed more effectively by antibacterial wipes than by microfiber [13]. Disinfectants may be applied using inadequate contact times. Failure of housekeepers to use an adequate number of wipes per room can result in poor cleaning of surfaces [6]. Use of wipes without sufficient antimicrobial activity against target pathogens can result in poor disinfection of surfaces and can lead to spread of pathogens from one surface to another [14, 15]. Binding of quaternary ammonium disinfectants to cloths made of cotton or wipes containing substantial amounts of cellulose may reduce the antimicrobial efficacy of the disinfectant [16, 17]. At least one laboratory-based study has shown that detergent wipes have variable ability to remove pathogens from surfaces, and may in fact transfer pathogens between surfaces [18].

Inappropriate over-dilution of disinfectant solutions by housekeepers or by malfunctioning automated dilution systems may result in applying disinfectants using inappropriately low concentrations [9, 17]. For example, an investigation of housekeeping practices at a large teaching hospital included an audit of 33 automated disinfectant dispensing stations that mix concentrated disinfectant with water to yield a desired in-use quaternary ammonium concentration of 800 ppm [17]. Quaternary ammonium concentrations of solutions dispensed were tested using commercially-available test strips. The audit revealed that several dispensing stations yielded solutions with less than 200 ppm, approximately 50 % of stations delivered solutions with 200 to 400 ppm. An investigation revealed several flaws in the dispensing system. Inexpensive test strips and more complicated titration kits are available to monitor quaternary ammonium concentrations of disinfectants.

Contamination of disinfectant solutions can occur, particularly if recommendations for their use are not followed [19‐21]. For example, Kampf et al. recently reported that 28 buckets from 9 hospitals contained surface-active disinfectants (e.g., quarternary ammomium solutions) that were contaminated with Achromobacter or Serratia strains [21]. Buckets and roles of wipes had not been handled according to manufacturer recommendations. In studies that involved culturing high-touch surfaces in patient rooms before and shortly after housekeepers had performed routine cleaning, we found that cultures obtained from several surfaces in one room after cleaning yielded large numbers of Serratia and smaller numbers of Achromobacter which were not present before cleaning [Fig. 1] [20]. The housekeeper’s bucket of quaternary ammonium-based disinfectant contained 9.3 × 10⁴ CFUs/ml of gram-negative bacilli (mostly Serratia marcescens and fewer numbers of Achromobacter xylosoxidans). Pulsed-field gel electrophoresis demonstrated that Serratia isolates recovered from the disinfectant were the same strains as those recovered from surfaces in the patient room. Genome sequencing of one of the Serratia strains by collaborating investigators revealed that it contained four different qac resistance genes that permitted the organism to grow and survive in the disinfectant (unpublished data). If disinfectant contamination is suspected, a sample of the product can be used to inoculate a broth medium or solid agar containing neutralizers effective against the active agent(s) in the disinfectant solution.

Numerous studies have found that standard manual cleaning or disinfection of surfaces can reduce, but often does not eliminate, important pathogens such as C. difficile, staphylococci including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), and multi-drug-resistant Acinetobacter [7, 22‐28]. Failure to adequately disinfect patient rooms at the time of hospital discharge contributes to the increased risk of acquisition of resistant pathogens among patients admitted to a room where the prior room occupant was colonized or infected with a multidrug-resistant pathogen [29‐31].

In order to improve standard cleaning and disinfection practices, it is recommended that the practices of housekeepers be monitored and that they receive feedback regarding their performance. However, monitoring of housekeeper performance is often not performed as frequently as needed, if at all [10]. Recently, fluorescent marking systems (Fig. 2) and ATP bioluminescence assays (Fig. 3) have proven useful for evaluating cleaning practices and providing housekeepers with feedback [32, 33]. Unfortunately, such objective means of monitoring the adequacy of cleaning/disinfection practices are not routinely used in many facilities [10]. Perhaps the lack of monitoring of housekeepers is due in part to the fact that monitoring activities can be time-consuming and must be conducted on an ongoing basis in order to be effective [34].

Given the multitude of challenges to achieving and maintaining adequate cleaning and disinfection in healthcare facilities, there is a need to consider the use of modern technologies designed to improve disinfection of surfaces in hospitals. New technologies fall into several categories, including: (A) new liquid surface disinfectants, (B) improved methods for applying disinfectants, (C) self-disinfecting surfaces, (D) light-activated photosensitizers, and (E) no-touch (automated) technologies.

Aerosolized hydrogen peroxide systems that utilize 3 to 7 % hydrogen peroxide with or without the addition of silver ions have been evaluated by several investigators [25, 73‐79]. Aerosols (which are not vapor) generally have particle sizes ranging from 2 to 12 μ, are injected into a room, followed by passive aeration. These systems have been shown to significantly reduce bacteria, generally a 4 log₁₀ reduction of spores, although in several studies spores were not completely eradicated. One system has a sporicidal claim from the EPA in the United States. In one study, use of the aerosolized hydrogen peroxide system was associated with a reduction in C. difficile infection, and possible reduction of MRSA acquisition in a second study [25]. Like many other strategies in infection control, there are currently no randomized controlled trials of the efficacy of these systems in preventing health-care-associated infections.

A “dry gas” vaporized hydrogen peroxide system that utilizes 30 % hydrogen peroxide has been shown to be effective against a variety of pathogens, including Mycobacterium tuberculosis, Mycoplasma, Acinetobacter, C. difficile, Bacillus anthracis, viruses, and prions [80‐83]. In before/after studies, dry gas vaporized hydrogen peroxide system, when combined with other infection control measures, appears to have contributed to control of outbreaks of Acinetobacter in a long-term care facility and in two intensive care units in a hospital [84‐86]. However, long cycle times have made it difficult to implement this system in healthcare facilities.

A micro-condensation hydrogen peroxide vapor system, which utilizes 35 % hydrogen peroxide, is effective in eradicating important pathogens including MRSA, VRE, C. difficile, Klebsiella, Acinetobacter, Serratia, Mycobacterium tuberculosis, fungi, and viruses. Laboratory-based and in-hospital studies documented significant reductions (often 10⁶ log₁₀) of a number of these pathogens, with 92 to 100 % reduction of pathogens on surfaces [23, 83, 87‐93]. In before/after trials, when used in conjunction with other measures, the micro-condensation hydrogen peroxide vapor system appears to have contributed to control of outbreaks caused by MRSA, multi drug-resistant Gram-negative bacteria, and C. difficile [78, 87, 94‐99]. A prospective, controlled trial performed by Passaretti et al. demonstrated significant reduction in the risk of acquiring multidrug-resistant organisms (MDROs), especially VRE [30]. It has also been used to decontaminate the packaging of unused medical supplies removed from isolation rooms, instead of discarding such items [100]. This system has also been used to decontaminate rooms previously occupied by patients with the Lassa fever and Ebola virus infection [101, 102]. Despite the demonstrated ability of this system to eradicate nosocomial pathogens from surfaces, concerns over its cost and room turn-around-times have hampered adoption of this technology in healthcare settings. At least one study found that the micro-condensation hydrogen peroxide system can be implemented in hospitals when census levels are relatively high [103]. Recent improvements in the efficiency of the system permit more rapid turn-around-times than earlier equipment, which may lead to wider adoption. To date, there are no randomized, controlled trials establishing the impact of the micro-condensation hydrogen peroxide system on reduction of healthcare-associated infections. Other vapor- or aerosol-based no-touch disinfection technologies that have been described, but whose adoption appears to be limited include gaseous ozone, chlorine dioxide gas, and saturated steam systems [104‐109].

Automated mobile ultraviolet light devices that continuously emit UV-C in the range of 254 nm can be placed in patient rooms after patient discharge and terminal cleaning has been performed. A number of these devices can be set to kill vegetative bacteria or to kill spores. These systems often reduce the VRE and MRSA by four or more log₁₀, and C. difficile by 1–3 log₁₀ [110‐118]. In one comparative trial, a continuous UV-C light system resulted in lower log reductions than a micro-condensation hydrogen peroxide vapor system [119]. Advantages of the mobile, continuous UV-C light devices include their ease of use, minimal need for special training of environmental services personnel, and unlike hydrogen peroxide vapor systems, the ability to utilize the devices without having to seal room vents or doors. Recently, a prospective, multicenter randomized controlled trial comparing a mobile continuous UV-C light system with standard and other enhanced surface disinfection methods has been completed [120]. Results of the trial should be published in the near future.

A pulsed-xenon device, which does not use mercury bulbs to produce UV light, emits light in the 200–320 nm range. It has been shown to significantly reduce pathogens in patient rooms [121‐127]. The manufacturer recommends placing device in 3 locations in a room with 5–7 min cycles (shorter than with some continuous UV-C systems). While a few studies utilizing the device reported reductions in C. difficile infection [122, 127], a more recent 8-month study in a large institution found no significant reduction in C. difficile infection rates hospital-wide or on four units with high C. difficile infection rates [128]. One carefully-performed trial which compared the pulsed-xenon system with a continuous UV-C light device found that log₁₀ reductions of pathogens achieved with the pulsed-xenon system were lower than with the continuous UV-C light device [129]. Additional evaluation of the pulsed-xenon UV system by independent investigators is needed.

High-intensity narrow-spectrum (HINS) light, which is visible violet-blue light in the range of 405 nm has been tested as a means of disinfecting air and surfaces and hospital rooms. This technology targets intracellular porphyrins that absorb the light and produce reactive oxygen species [130‐132]. Its antimicrobial efficacy is lower than UV-C light, but it can be used in areas occupied by patients. In one study, continuous HINS light showed a 27 to 75 % reduction in surface contamination by staphylococci compared to control areas [131]. Further investigation of this technology, including its level of activity against C. difficile, appears warranted.

An enclosed air purifying system designed for use by NASA utilizes UV-activated titanium dioxide photocatalytic reactions to oxidize volatile organic compounds and airborne microorganisms. Since aerosolization of pathogens such as S. aureus and C. difficile during patient care activities is known to occur, there may be some interest in using such systems in patient rooms to reduce airborne bacteria may settle onto environmental surfaces [133].

Given the increasing interest in the above-mentioned new technologies for cleaning and disinfection of environmental surfaces, the Agency for Healthcare Research and Quality (AHRQ) recently commissioned an expert panel to review data regarding these modern technologies. The panel concluded that there is a relative lack of comparative studies addressing the relative effectiveness of various cleaning, disinfecting and monitoring strategies, and that future studies are needed that directly compare newer disinfecting and monitoring methods to one another and with traditional methods [4].