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Exploring a New Paradigm for Cleaning Efficacy

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By Kelly M. Pyrek

Just how efficacious are the cleaning and disinfection interventions performed in healthcare institutions? And what standard are hospitals using to evaluate cleaning efforts?  While it has been suggested that the food industry cleanliness standard (surface bioburden level of <2.5 cfu/cm²) be adopted in healthcare as an indication of relative cleanliness, there is still a lack of conclusive evidence that these levels of contamination relate to the prevention of healthcare-associated infections (HAIs).

A historical review to place this topic in perspective is in order here. As Dancer (2004) observed, “There may be a link between dirty hospitals and the rising numbers of hospital-acquired infections but there is little evidence to be able to substantiate this at present ... Unfortunately, the mechanisms for evaluating the quality of hospital cleaning regimens are limited.”

Dancer (2004) also outlined the challenges associated with trying to measure cleaning efficacy: “The difficulties in measuring cleaning efficacy are compounded by the lack of standardized methodologies and are rarely quantitative. Environmental screening usually takes place on an ad hoc basis after an outbreak, but it is patently impossible to screen the entire surface of a ward and finding the outbreak strain is not guaranteed. Furthermore, organisms still have to be transmitted to patients. As this is thought to occur via staff hands, strategies for controlling HAI are more likely to favor improvements in hand hygiene than comprehensive screening programs. Cost-benefit and lack of standardized methodologies might also explain the perceived reluctance of private cleaning companies to participate in screening. Certainly, most microbiologists would be cautious about taking environmental samples from hospital wards on a routine basis.” She adds, “No one set of standards exists for general hospital wards, however, and there is considerable variation in sampling methodologies and quantitative reporting. There are further differences in whether sampling is carried out routinely or in response to an infection incident. This makes it difficult to compare fluctuating situations in a ward, between wards and between different hospitals, let alone investigate specific levels of contamination in relation to infection risk.”

In a time when commercial ATP systems were either in their infancy or unavailable, Dancer (2004) called for bacteriological standards with which to assess clinical surface hygiene in hospitals, based on those used by the food industry. The first standard concerns any finding of a specific ‘indicator’ organism, the presence of which suggests a requirement for increased cleaning. Indicators would include Staphylococcus aureus, including methicillin-resistant S. aureus, Clostridium difficile, vancomycin-resistant enterococci and various Gram-negative bacilli. The second standard concerns a quantitative aerobic colony count of <5 cfu/cm2 on frequent hand-touch surfaces in hospitals. As Dancer (2004) noted, “As cleaning could be a cost-effective method of controlling HAI, it should be investigated as a scientific process with measurable outcome. To achieve this, it is necessary to adopt an integrated and risk-based approach. This would include preliminary visual assessment, rapid sensitive tests for organic deposits, and specific microbiological investigations.” She adds, “Both indicator organisms and those gathered within numerical counts can be identified, quantified, documented and audited. The methods required are simple, cheap and reproducible and could be adopted by any healthcare institution with access to a clinical microbiological laboratory. Furthermore, as evidence becomes available, these standards can be modified to reflect the overall risk of infection, and adapted to high-risk patients, high-risk units and emergency or outbreak situations.”

Lewis, et al. (2008) acknowledge that “Calls have been made for a more objective approach to assessing surface cleanliness. To improve the management of hospital cleaning the use of adenosine triphosphate (ATP) in combination with microbiological analysis has been proposed, with a general ATP benchmark value of 500 relative light units (RLU) for one combination of test and equipment.” In their study, Lewis, et al. (2008) used this same test combination to assess cleaning effectiveness in a 1,300-bed teaching hospital after routine and modified cleaning protocols. Based upon the ATP results a revised stricter pass/fail benchmark of 250 RLU is proposed for the range of surfaces used in this study. This was routinely achieved using modified best practice cleaning procedures which also gave reduced surface counts with, for example, aerobic colony counts reduced from >100 to <2.5 cfu/cm2, and counts of Staphylococcus aureus reduced from up to 2.5 to <1 cfu/cm2 (95 percent of the time). The researchers say that benchmarking is linked to incremental quality improvements and both the original suggestion of 500 RLU and the revised figure of 250 RLU can be used by hospitals as part of this process, and that they can also be used in the assessment of novel cleaning methods.

Al-Hamad and Maxwell (2008) concur that “Although microbiological standards have been proposed for surface hygiene in hospitals, standard methods for environmental sampling have not been discussed.” In their study, Al-Hamad and Maxwell (2008) sought to assess the effectiveness of cleaning and disinfection in critical-care units using the wipe-rinse method to detect an indicator organism and dip slides to quantitatively determine the microbial load. Frequent hand-touch surfaces from clinical and non-clinical areas were microbiologically surveyed, targeting both methicillin-susceptible (MSSA) and methicillin-resistant (MRSA) Staphylococcus aureus. A subset of the surfaces targeted was sampled quantitatively to determine the total aerobic count. MRSA was isolated from nine (6.9 percent) and MSSA was isolated from 15 (11.5 percent) of the 130 samples collected. Seven of 81 (8.6 percent) samples collected from non-clinical areas grew MRSA, compared with two (4.1 percent) from 49 samples collected from clinical areas. Of 116 sites screened for the total aerobic count, nine (7.7 percent) showed >5 cfu/cm2 microbial growth. Bed frames, telephones and computer keyboards were among the surfaces that yielded a high total viable count. There was no direct correlation between the findings of total aerobic count and MRSA isolation; however, Al-Hamad and Maxwell (2008) suggest that combining both standards will give a more effective method of assessing the efficacy of cleaning/disinfection strategy. They add that further work is required to evaluate and refine these standards in order to assess the frequency of cleaning required for a particular area, or for changing the protocol or materials used.

Without definitive standards for defining cleanliness, infection preventionists and environmental services directors must evaluate the literature as well as the current chemistries and technologies in the marketplace to determine a plan of action for their institutions. It can be a confusing process, as Bartlett (2014) observes, “Surfaces near patients are increasingly being recognized as important links in transmission of HAIs. It seems obvious that clean surfaces pose a lower risk for transmission than contaminated surfaces, but the relative contributions of different cleaning products, application devices, and new technologies are not clear. U.S. Environmental Protection Agency-approved disinfectants must demonstrate efficacy against viruses, bacteria, and spores, but there is no requirement to assess the clinical effectiveness of a product.”

Enter Philip Carling, MD, of Carney Hospital and Boston University School of Medicine, and colleagues, who hoped to learn, upon completion of their two-phase evaluation, about the clinical effectiveness of two surface disinfectants in a general acute-care hospital. What came out of this study is a new way of thinking about quantifying bioburden reduction while monitoring the possible impact of differences in cleaning thoroughness. Essentially, Carling and colleagues developed a system for the simultaneous assessment of both the cleaning process and cleaning products.

The products compared were a traditional quaternary ammonium compound (QAC) and a novel peracetic acid/hydrogen peroxide disinfectant (ND) as part of terminal room cleaning. As a result of QAC cleaning, 93 (40 percent) of 237 cleaned surfaces confirmed by fluorescent marker removal were found to have complete removal of aerobic bioburden. During the ND phase of the study, bioburden was removed from 211 (77 percent) of 274 cleaned surfaces. Because there was no difference in the thoroughness of cleaning with either disinfectant (65.3 percent and 66.4 percent), the researchers say that significant difference in bioburden reduction can be attributed to better cleaning efficacy with the ND.

In essence, the researchers concluded that in the context of the study design, the ND was 1.93 times more effective in removing bacterial burden than the QAC. Furthermore, the researchers say that study design represents a new research paradigm in which two interventions can be compared by concomitantly and objectively analyzing both the product and process variables in a manner that can be used to define the relative effectiveness of all cleaning and disinfection interventions.

Deshpande, et al. (2014) also compared the efficacy of a PA/H2O2 sporicidal disinfectant with a 1:10 dilution of bleach against vancomycin-resistant enterococcus (VRE), MRSA and Clostridium difficile spores in a laboratory setting. The researchers reported that PA/H2O2 effectiveness was not affected by the presence of organic material, whereas bleach was significantly impaired by the presence of organic material. When used in a clinical setting, both bleach and PA/H2O2 eliminated C difficile, MRSA, and/or VRE contamination on bed rails and bedside tables. On floors where it was compared with a quaternary ammonium disinfectant, only PA/H2O2 significantly reduced C difficile, MRSA, and/or VRE contamination.

Bartlett (2014) asserts that a significant limitation of the Carling and Deshpande studies is “the universal lack of data defining the relative risk for transmission of healthcare-associated pathogens based on specific levels of microbial contamination of surfaces (bioburden).” She adds, “Given that there is no evidence-based standard of ‘how clean is clean,’ interpretation of the reduction in bacterial burden is unclear. Some have suggested using the same threshold as in food preparation surfaces (<2.5 colony-forming units [CFU]/cm2), but whether this level of contamination is associated with a lower risk for transmission of healthcare-associated pathogens is unknown. In this study, only 1.7 percent of cleaned surfaces would have been defined as a failure (>2.5 CFU/cm2), and 85 percent of surfaces would have been counted as ‘clean’ prior to actual cleaning. Stated another way, using only post-cleaning colony counts, 98 percent of surfaces would be declared ‘clean,’ whereas using the fluorescent marker showed that only 66 percent of surfaces were ‘cleaned.’ Whether the increased effectiveness of PA/H2O2 compared with the quaternary ammonium disinfectant or 1:10 dilution of bleach will result in clinical reductions in transmission of environmental pathogens and improved patient outcomes requires further evaluation. However, the technique described by Carling and colleagues, which pairs evaluation of thoroughness of cleaning (using fluorescent marking) with effectiveness of the cleaning product itself (using colony counts from dip slides), is novel. The study authors commented on the potential for using this paradigm to study the relative clinical efficacy of other cleaning and disinfection products, materials, and technologies. Are microfiber cloths better than paper towels? Are disposable disinfectant wipes better than towels soaked in disinfectant? This brings us back to the important question: Does it matter for patients? We don’t have the answers yet, but the techniques described in these articles, combined with studies evaluating the impact of ‘better cleaning’ on patient outcomes, will be instrumental to advancing the science of preventing HAIs.”

One stumbling block could be the methodologies embraced by the Environmental Protection Agency (EPA) when evaluating and approving disinfectants for the disinfection of surfaces that harbor and transmit pathogens. As Carling, et al. (2014) explain, “Although the EPA process for evaluating the intrinsic efficacy of disinfectants in terms of their bactericidal, viracidal and sporicidal efficacy provides the basis for EPA certification labeling, actual assessment of clinical effectiveness is not used as part of the approval process.”

“It’s frustrating that we have no way of clinically evaluating this world of environmental hygiene,” Carling says. “The reality is that almost all studies out there on technologies such as HPV or ultraviolet light have been outbreak situations, and you can’t rely on outbreak situations to dictate practices in non-outbreak situations — it’s not good science. Now that we have some of these new disinfectants, it’s time to ask, are they really better and are they worth it in terms of expense over traditional cleaners and disinfectants. If these new disinfectants are as good as bleach, efficacy-wise, then why not consider them? But first you have to find a way of saying they are equivalent. The EPA approval system is limited. They are providing a level of basic laboratory efficacy of a chemistry. Not to say that’s not important, but there’s no reason not to take the next step in evaluating cleaning efficacy.”

The process that Carling and colleagues used is easily replicated by hospitals, he says. Before cleaning each room, 12 surfaces were concurrently marked with an invisible fluorescent marker and cultured for aerobic bacteria on an adjacent surface to the left of the fluorescent marker using an agar dip slide (10 cm2 surface area) with neutralizer. The slides were incubated for 24 hours, and the total aerobic colony count was determined by the test site microbiology laboratory. Following room cleaning, a black light was used to determine whether the fluorescent marker had been completely removed (the surface was cleaned) as previously described, and a second dip slide culture of the surface adjacent and to the right of the fluorescent marker site was obtained and processed. Culture results were recorded as the absolute number of aerobic colonies per slide after incubation (colony-forming units [CFU]/10 cm2). Carling says that surfaces that had no detectable aerobic bacteria before cleaning were excluded from additional analysis because the effectiveness of the disinfectant on such a surface could not be evaluated. Surfaces that had been overlooked during cleaning as evidenced by the persistence of the fluorescent marker were tabulated to determine the thoroughness of cleaning in each phase of the study. Only surfaces with no detectable bacterial burden (0 CFU) after documented cleaning were defined as effectively cleaned for the purpose of the study.

As Carling, et al. (2014) explain, “Over the past decade, dip slide systems have been used extensively to study the epidemiology of bacterial healthcare environmental surface contamination but have not been used to compare the clinical efficacy of surface disinfectants. Culture swab samples have been used in the evaluation of disinfection cleaning of specific pathogens, such as VRE, MRSA, Clostridium difficile and Acinetobacter, but the high level of non-quantitative sensitivity (standard culture area is 100 cm2) of swab samples or sponge culture systems precludes their use in general bioburden evaluation. Furthermore, it is likely that the performance variability when quantitatively swabbing an estimated or template 100-cm2 surface is prone to both user variability and possible intervention bias. Although the dip slide system, because of its small culture surface, would be expected to have low sensitivity for frequently identifying by culture anaerobic healthcare-associated pathogens that are typically found at very low densities on or near patient surfaces, it is reasonable to assume that bioburden removal represents a good surrogate for healthcare-associated pathogen removal, because many studies have confirmed the absence of disinfectant resistance in pathogens such as MRSA, VRE, and drug-resistant Gram-negative organisms.”

The researchers add, “The modeling used in this study fulfills all elements of what Kuhn first described as a paradigm shift in 1962. Kuhn specifically noted that such a shift leads to a ‘reconstruction of investigation’ that allows for ‘the emergence of highly directed, or paradigm-based research.’ As a result of the described modeling, two interventions can be compared by concomitantly and objectively monitoring the ‘process and product’ elements of disinfection cleaning. This has potential for effectively defining the relative clinical efficacy of cleaning and disinfecting materials such as microfiber cloth, disposable disinfectant wipes, detergents without disinfectant activity, all forms of nontouch disinfection technologies, and self-disinfecting surfaces. Such studies may then begin to objectively clarify best practices for decreasing the risk of pathogen transmission from contaminated surfaces to patients through the use of various cleaning modalities and chemistries while providing guidance for more in-depth clinical studies of cost-benefit issues and healthcare-associated pathogen transmission prevention.”

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