Chemical disinfectants: Controversies regarding their use in low risk healthcare environments (part 1)

Abstract

In recent years, the number of disinfectants designed to decontaminate healthcare environments and reusable, non-invasive care equipment (NICE) has increased markedly, making the selection of the most appropriate disinfectant a somewhat daunting prospect. In addition to the microbial challenge, there are numerous factors to consider including: efficacy; range and speed of activity; stability of the ingredients; compatibility of the disinfectant with surfaces; inactivation of the disinfectant by organic matter; method of application; convenience; health and safety concerns; and cost. While the microbial challenge continues to evolve, and novel disinfectants continue to emerge, guidance updates have been notably absent. Most healthcare surfaces belong to a UK-defined category of ‘low risk’ for which guidance dictates ‘cleaning and drying is usually sufficient’. This paper assesses the evidence and arguments regarding the use of disinfectants for low-risk healthcare surfaces. A novel subcategorisation of ‘low risk’ is presented to provide a more specific up-to-date disinfectant needs assessment.

Introduction

Over the past decade, there has been an unprecedented increase in new/modified disinfection products designed to decontaminate reusable, non-invasive care equipment (NICE) and the healthcare environment. For such tasks, novel modes of supply have also increased, such that disinfectants can now be delivered remotely via a vapour, mist or aerosol (hydrogen peroxide), or as light beams (ultraviolet light) (Rutala and Weber, 2013a). Also available are impregnated wipes (e.g. alcohol, chlorine-releasing agents, peracetic acid or hydrogen peroxide) (Abreu et al., 2013; Boyce and Havill, 2013; Carter and Barry, 2011; Gonzalez et al., 2015). Traditional disinfectants, which can be applied as a solution directly using paper towels, single cloths or mop and bucket are also still available, e.g. chlorine-releasing agents, including sodium dichlorisocyanurate (tablets or granules) and quaternary ammonium compounds (Gerba, 2015; McDonnell and Russell, 1999). Finally, some established disinfectants have been modified to affect their speed of action or lessen their impact on the environment or equipment, e.g. peracetic acid and hydrogen peroxide (Doan et al., 2012; Gonzalez et al., 2015).

The wide variety of options can leave the user confused over which disinfectant(s) is/are most appropriate for the required task. The use of disinfectants, like most things in the infection prevention world, is based as much on opinion as science. In this, the first of two papers, controversies on disinfectant use in healthcare environments and for reusable NICE will be explored.

Cleaning, disinfection, decontamination and sterilisation

Decontamination is one or more procedures that result in a lack of residual pathogens. According to the Medicines and Healthcare products Regulatory Agency (MHRA), it can involve: cleaning alone; or cleaning followed by disinfection; or cleaning followed by sterilisation (MHRA, 2010). Sterilisation is a process that makes any item free from all living organisms (MHRA, 2010). Disinfection will reduce the number of—but not remove all—organisms so that the object is subsequently unlikely to cause infection when used. Cleaning removes substantial amounts of any material which is not part of the item (Hoffman et al., 2004). Although cleaning removes soil, and the organisms within the soil, there is an absence of a disinfectant to act on any remaining organisms. By removing soil, cleaning serves three goals:

• to reduce the microbial challenge and increase the margin of safety for disinfection;

• to prevent inactivation of the disinfectant by soil;

• to enable the disinfectant to gain access to the residual micro-organisms on the surface (Hoffman et al., 2004; Centers for Disease Control and Prevention [CDC], 2008).

There is no word for a procedure which involves cleaning and disinfection alone, which can lead to some confusion: for example, Health Facilities Scotland (HFS 2016) uses the terms ‘Terminal clean’ for a procedure which involves disinfection and ‘Discharge clean’ for a procedure that does not.

What comes first: cleaning or disinfection?

Traditionally, a disinfectant was considered most likely to achieve disinfection if it was applied after cleaning (Hoffman et al., 2004). Apart from decontaminating blood spillages, the generally accepted adage was to clean before disinfection. However, some novel products, including impregnated wipes and sprays, contain both surfactants and disinfectants meaning that these procedures can be performed simultaneously. The efficacy of a (cleaning and disinfecting) impregnated wipe in achieving disinfection is dependent on the following:

• the wipe contains sufficient surfactants, disinfectants and wetness while the procedure is performed (and for a stated contact time);

• the disinfectant can achieve disinfection given the microbial and soil challenge;

• the wipe is used in a systematic way to remove gross soil and then to clean and disinfect the entire surface area.

The efficacy of cleaning and disinfection of any pre-impregnated wipe requires that both the disinfectant has been tested as well as the delivery method, i.e. suspension tests and surface tests with a wiping action. Those selecting disinfectants also need assurance of the benefits of use within clinical settings, e.g. minimal time requirements to prepare, perform and remove residues/waste.

Does today’s microbiological challenge necessitate disinfection?

In a review of the environmental survival times of micro-organisms, Kramer et al. (2006) showed that all clinically relevant pathogens acquired via contact with surfaces remain viable long enough to present a risk to the next patient. These pathogens are referred to by Infection Prevention and Control Teams (IPCTs) as alert organisms. Chemical disinfectants used in the healthcare environment must be able to kill these alert organisms and so minimise cross-transmission risk. While many alert organisms are resistant to antibiotics, there is scant evidence that these antibiotic-resistant organisms (AROs) are more difficult to kill with disinfectants than sensitive pathogens, especially at in-use concentrations (CDC, 2008). However, there is a hierarchy of resistance to chemical disinfectants which is dependent on the organism’s structure (Russell, 1999). Apart from C. difficile spores, most micro-organisms that could present a cross-transmission risk from the environment or from reusable NICE are sensitive to a wide range of disinfectants (Rutala and Weber, 2013b). The following bullet points summarise how the presence of alert organisms, including AROs, in the healthcare setting imparts risk:

• alert organisms survive on surfaces in care environments and are readily transferred to healthcare workers, subsequent patients and other surfaces via contact;

• hand hygiene and glove use is insufficiently well practised to negate the risk;

• alert organisms are not solely found in the environment/equipment associated with known positive patients. This may be influenced by an:

  • inability to identify all persons who present a risk in real time;

• inability to provide isolation facilities for all patients who present a cross-transmission risk (CDC, 2008; Kramer et al., 2006; Loveday et al., 2014a; Mitchell et al., 2015; Poole et al., 2016; Wigglesworth and Wilcox, 2006).

Cross-transmission with AROs increases the risk of a healthcare-associated infection (HAI) developing with reduced therapeutic options. But, importantly, patient harm may result even in the absence of infection, e.g. ARO-colonised patients may be isolated and have their antibiotics changed to a more toxic combination (Public Health England, 2013). In addition, action is required, including the screening of roommates when a newly colonised patient is identified (Public Health England, 2013). It is therefore reasonable to argue that AROs in the healthcare environment and on reusable NICE present sufficient risk, such that disinfection is required more routinely than currently recommended.

The microbial challenge from specific environments and equipment is invisible and, therefore, in the absence of sampling, unknowable. It is also persistent, as people remain colonised with AROs for significant periods of time, resulting in ongoing microbial contamination – even in the absence of visible soil. The microbial challenge within the care environment and on reusable care equipment can include: viruses (respiratory, blood-borne [BBV] and enteric); bacteria (Gram-positive and -negative organisms); fungi; and the spores of C. difficile (Kramer et al., 2006). The main defence against this microbial challenge is cleaning.

Cleaning: a complex system

Hospital cleaning is a complex system and complex systems always operate in a degraded mode (Cook, 2000), e.g. there will always be some resource that is absent and when additional cleaning is required, there are often insufficient resources available. Hence, on any given day, not everything scheduled for cleaning will be cleaned. Increased hospital throughput and occupancy means that the number of surfaces to be decontaminated and readied for subsequent patients has increased, with a concomitant increase in time pressure. Cleaning has poor and delayed feedback loops; in addition, visible cleanliness is an inadequate indicator of the presence of soil or microbes (Mulvey et al., 2011). Moreover, as cleaning often involves visibly clean surfaces, areas are frequently missed. One review found from eight reports that 40% of near-patient surfaces were not cleaned as per protocols (Carling and Bartley, 2010).

In the absence of direct evidence, it is difficult to identify whether inadequate cleaning was due to:

• a failure of process (inadequate cleaning protocol); or

• a failure to follow process (the cleaning process being poorly implemented [resource or practice issues]).

In addition to assessing visual monitoring, Mulvey et al. (2011) also examined surfaces using microbial screening and adenosine triphosphate bioluminescence. They found that although cleaning reduced levels of soil by 32%, and reduced microbial surface contamination, it eliminated neither soil nor microbes. However, another study found that extra cleaning was associated with reduced HAI and costs (Dancer et al., 2009). That both are vital is evidenced by researchers, who showed a significant reduction in alert organisms and HAI using a disposable disinfectant wipe but only when cleaning compliance was ⩾ 80% (Alfa et al., 2015). Next-patient-room cross-transmission provides evidence of inadequate decontamination including disinfection; however, in the Mitchell et al. (2015) review, this phenomenon was identified when the prior occupant was known to be colonised or infected (hence, this could be a failure of process and/or a failure to follow process).

Another factor which has (anecdotally at least) resulted in increased use of disinfectants is the financial penalties for more than expected cases of C. difficile infection (CDI). One senior infection prevention and control nurse consultant recently stated in a personal communication: ‘We started using them because we had to throw everything at CDI (the timing of which predates my tenure) and now it ain’t broke so we ain’t gonna fix it.’ This pressure not to have excess cases of CDI makes it appealing to increase disinfectant use and to see disinfectants as a panacea (perhaps even as a supplement to inadequate cleaning and hand hygiene). However, if cleaning is poorly done, it is likely that the disinfection procedure will be performed likewise. Clearly the guidance on decontamination needs further exploration.

Problems with guidelines…

Guidelines for the decontamination of low-risk environments have not kept pace with the increasing evidence of risk and the burgeoning disinfectant options. Furthermore, there is variation in the application of the precautionary principle. These two issues are discussed below.

Guidance for low-risk environments and equipment

Spaulding set out criteria for the sterilisation and disinfection of patient-care items and equipment, devising three categories: critical; semi-critical; and non-critical (Spaulding, 1957). Non-critical items comprise those designed to make contact with intact skin. This would include all the reusable NICE and environmental surfaces. In the UK, a modified Spaulding classification (high, intermediate and low risk) was adopted based on the risk of HAI arising from ‘medical devices’ (MHRA, 2010). This classification was further developed to include a category ‘minimal’ to take account of the environmental surfaces (Hoffman et al., 2004). However, these low and minimal classifications still provide scant direction, other than stating that ‘cleaning and drying is usually sufficient’. Precisely when cleaning and drying is insufficient is undefined. The ‘low-risk’ category used by the MHRA (2010) and Hoffmann et al. (2004) includes items that will be ‘in contact with healthy skin’. Technically, this category includes items which are heavily contaminated with, e.g. faecal matter, which may be inadequately decontaminated by cleaning. Disinfection is required for some items in the intermediate category which are ‘contaminated with particularly virulent or readily transmissible organisms’ (MHRA, 2010). However, this criterion is impossible to apply as visual inspection cannot determine whether any item, soil or surface, meets the definition. An additional recommendation in Epic3 advises ‘disinfectants should be considered for cases of infection and/or colonisation, when a suspected or known pathogen can survive in the environment and environmental contamination may contribute to the spread of infection’ (Loveday et al., 2014b). This recommendation could be seen to support the widespread use of disinfectants, given it is impossible to know all who are colonised and it is easy (and perhaps considered safer) to suspect everyone is. The Department of Health’s Code of Practice (2008, p. 26) is vague regarding the contents of a required disinfectant policy, stating only ‘The use of disinfectants is a local decision and should be based on current accepted good practice’.

The application or omission of the precautionary principle

Current UK decontamination guidelines vary in the use of the precautionary principle, e.g. disinfect regardless of knowing whether a pathogen is present, and at other times disinfect only when there is evidence of a recognised risk. This is illustrated in the standard precaution recommendation for the decontamination of blood and body fluid (BBF) spillages where blood-borne viruses may be present. Recommendations require immediate decontamination including disinfection for blood spillages (Health Protection Scotland [HPS], 2016a). However, this precautionary principle is deemed unnecessary for other alert organisms, such as AROs or Clostridium difficile, which are shed and remain viable in the environment and on equipment for significant time periods. Disinfection is only recommended when patients who used equipment and environments were known or suspected of being colonised with alert organisms (HPS, 2016b). This variation exists even though it is recognised that we are unable in real time to identify everyone who is colonised, and contamination has been identified outwith areas where patients with known AROs are cared for (Poole et al., 2016; Weber et al., 2013). Thus, the question still to be answered is: when and where should disinfectants be used as part of a routine decontamination regimen?

The use of disinfectants between patients

Arguments for and against the routine use of disinfectants between patients have been published (CDC, 2008; Rutala and Weber, 2001). The CDC advocates routine disinfection, but the UK guidance (if not practice) remains to disinfect only in the presence of a recognised risk or BBF spillage. However, some of these arguments need revisiting. Before doing so it is prudent to remind ourselves of the motivation behind such guidance.

Guidance aims to:

• provide a safe environment (equipment and surfaces) which is adequately decontaminated;

• reduce the risk of cross-transmission through contact;

• mitigate risks to people and surfaces from decontamination procedures.

These goals exist in the context of modern healthcare: high throughput; vulnerable patients; unreliable scheduled cleaning; the inability to detect all patients colonised with alert organisms; undetected alert organisms surviving on surfaces; transmission risks from failures to decontaminate environments; pressure to reduce HAI; and pressure to reduce antibiotic usage. The increased usage of disinfectants can seem almost inevitable. However, arguments against this increased usage deserve careful scrutiny; six such arguments are explored below.

Six arguments against routine disinfection

Recolonisation happens too quickly

The oft-cited argument against increased disinfectant use is that although disinfectants kill micro-organisms, airborne dissemination of micro-organisms means that the recolonisation of sites takes place so quickly the disinfectant does not provide a patient benefit (Ayliffe et al., 1966, 1967). However, these excellent ground-breaking experiments were done on floors and occasionally walls before today’s nosocomial pathogens were prevalent. Also, much more is now known about the presence of organisms on frequently touched surfaces and the close patient equipment, e.g. the bed, bedframe, overbed table, etc., all of which will be exposed to the patient’s flora (Weber et al., 2013). Rapid recolonisation remains a valid argument against disinfectant use on communal floors without obvious body substance spills. However, this argument is not relevant for the post-discharge decontamination performed before the admission of a new patient. Disinfection post-discharge provides the opportunity to greatly reduce the risk of transmission via patient–surface contact. The anticipated infection prevention benefits of single room accommodation will only be realised if there is an absence of microbial risk from the prior room occupants.

Disinfectants damage the environment

Some chemical disinfectants are harmful to environmental surfaces, such that damage may render items uncleanable and shorten their life-span. Therefore, replacement costs need to be added to the cost of disinfectant usage. Some chemical disinfectants, including alcohols, are known to harden plastic and crack rubber. Chlorine can also damage the environment (Rutala and Weber, 2013a). However, newer disinfectants, such as hydrogen peroxide, contain active agents which degrade to harmless residues (oxygen and water) and are reported to be less damaging. Unfortunately, there is an absence of studies demonstrating this in clinical practice.

Disinfectants present an occupational hazard

The argument that chemical disinfectants present an occupational hazard is real but no more so than for the millions who use disinfectants in their own homes. Furthermore, the occupational hazard from undisinfected BBF spillages is also real and ubiquitous. Both of these risks are lessened by using personal protective equipment and following basic safety precautions.

Disinfectants themselves can become contaminated and present an outbreak risk

All fluids used in healthcare, even ‘sterile’ fluids, can become contaminated during manufacture or usage. One minireview of outbreaks related to antiseptics and disinfectants found 22 reports due to disinfectants alone – most provoked by poor ergonomic product presentation (Weber et al., 2007). This is also true of detergents. Ayliffe et al. (1966) reported that a dirty mop would result in floors contaminated with Gram-negative organisms, although they quickly died upon drying. Reliable quality assurance in production and improved product presentation can negate some of the risk, i.e. freshly prepared applications, appropriate storage and correct usage. Misreading instructions for use, misapplication of products and general misuse cannot be entirely avoided – but, as stated, this equally applies to detergents as disinfectants. However, the oversized disinfectant container, with its associated contamination/deactivation risk from soil, sunlight and other elements is largely a thing of the past. The ergonomic improvements in design and presentation of disinfection products have undoubtedly reduced the risk.

Disinfectants are costlier than detergents

This is a difficult argument to counter if the price comparison is a straight detergent versus disinfectant. To compare true costs, many other factors must be considered, e.g. the cost of a single case of CDI, the cost of even a small outbreak of an ARO or days lost due to ward closures. It is inherently difficult to demonstrate a counterfactual, i.e. the introduction of a disinfectant prevented infection or outbreak. However, one study, using an interrupted time series during 2006–2010, demonstrated a 72% reduction in C. difficile rates following the introduction of wipes (Carter and Barry, 2011). The introduction occurred at a time when other C. difficile prevention strategies were being implemented nationally. More studies of a similar nature are required to increase the evidence base for cost comparison. When considering costs, it is important to assess the financial implications of both success and failure

Micro-organisms could develop tolerance and resistance such that disinfectant-resistant organisms emerge

This hypothetical outcome merits constant vigilance. There are no data to suggest that the environmental microbiota in hospitals is developing resistance to chemical disinfectants. In assessing whether disinfectant-tolerant organisms will emerge and be problematic in clinical terms, the CDC concludes ‘the level of tolerance is not important because it is unlikely to compromise the effectiveness of disinfectants of which much higher concentrations are used’ (CDC, 2008).

What is the disinfectant needs assessment for today?

Current UK guidance is impossible to deploy in real time, as microbial risks in the absence of obvious body fluid spillages or gross soiling are not visible to the naked eye. In the complex and busy world of healthcare, what is needed is a simple system akin to that used for hand hygiene: five moments for when, six steps to perform and just two procedural options (wash or alcohol-based hand rub) (Sax et al., 2007). Devising a limited range of choices and ergonomic procedures will increase the chance of correct performance. To achieve this, there needs to be an expansion of the MHRA’s ‘low risk’ category and greater specification as to when disinfection is needed.

Logically, the low-risk category can be divided into three sub-categories (Table 1). First, the highest level (Low Risk I) includes blood spillages, where the risk is from possible BBVs. In addition, in this category is the risk of acquisition of C. difficile from spores which remain dormant in the environment. This applies to the environments/equipment of people recognised as having had CDI at some point. Both BBVs and CDI can cause life-threatening infections. This category also includes those with a recognised risk of carrying an alert organism (including AROs). Although the risk of ARO cross-transmission cannot be precisely quantified, it will be higher from those with recognised risk factors for carriage. Note while the first of these examples applies to the environment (all blood spillages), the last two apply to patient environments, which will need cleaning and disinfecting at regular intervals. Routine disinfection of floors would only be required in Low Risk I environments.

Table 1.

Sub-categorisation of “low risk” for effective decontamination.

Subcategory of low risk	Decontamination scenario	Requirement
Low risk I	Blood spillage (BBV risk)	Disinfect + clean
	Environments and equipment used on patients know to have / have had C. difficile	Clean + disinfect
	Environment and equipment used on patients known or suspected of having another alert organism	Clean + disinfect
Low risk II	Other body substance spillages	Clean + disinfect
	Before equipment moves between patient zones	Clean + disinfect
	Before patient zone is used by a different patient	Clean + disinfect
	Surface preparation before an aseptic technique	Clean + disinfect
Low risk III	Outwith the patient zone and none of the above apply	Clean

The middle-low-risk category (Low Risk II) includes four possible scenarios where cross-transmission from alert organisms cannot be excluded. Obviously, other body substance spillages will need decontamination (including disinfection) to negate a cross-transmission risk, e.g. faeces contains the highest microbial load of all body substances (10¹¹ per gram of stool; Sender et al. 2016). The next two scenarios incorporate a familiar-to-healthcare-worker concept of the patient zone, i.e. any time equipment enters a patient zone it will need to have been cleaned and disinfected, likewise before a patient enters a previously occupied patient zone the environment needs to have been cleaned and disinfected. The rationale for disinfection here is to reduce unrecognised, but periodically present, cross-transmission risks. Furthermore, as hands require decontamination between entering patient zones, logically equipment will need the same treatment. The final scenario in Low Risk II is for surfaces on which sterile equipment will be placed, e.g. trolley tops. Such practice would likely have prevented an outbreak that one of the authors dealt with, involving surfaces wiped down each morning with a tap-borne Stenotrophomonas sp. Finally, Low Risk III contains all other surfaces outwith the patient zone that are not specified in earlier categories.

As Boyce (2016) states, ‘manual cleaning and disinfection of environmental surfaces in healthcare facilities (daily and at patient discharge) are essential elements of infection prevention program[me]s’. It would be helpful therefore for those selecting regimens to have an approved list of disinfectants for environments and reusable NICE. To be approved the disinfectant would pass the relevant European Standard tests under expected in-use conditions and pass an environmental standard test (lack of harm to surfaces and people during and after use). Such a list in the UK would be a boon to both disinfectant manufacturers and those who select products to use.

Conclusion

The increase in novel and modified disinfectants has been mirrored by an absence of updated guidance. Current guidance is difficult to apply as it is impossible to determine whether alert organisms are present in people, soil and on surfaces. Manufacturers claim that their novel products support wider disinfectant use, i.e. there is now evidence of reduced risk of product contamination, harmless residues, absence of resistance development and reduced surface damage. With the increased need to prevent alert organism cross-transmission, coupled with evidence of missed cleaning opportunities, and the above developments, it is now possible to argue for the wider use of disinfectants using three subcategories of the original MHRA low-risk category. Publishing by IPCTs of their disinfectant usage and results is needed. An approved disinfectant list for low-risk surfaces would aid those selecting products.

Limitations

This paper has deliberately omitted mention of specific products or disinfectant modes of action. It is necessary for those selecting a disinfectant to possess reliable information regarding: the efficacy of the product; how it is to be used; whether toxic residues are left behind; the precautions necessary for use; any cost-comparisons; and the safety data. Hence the need for the second paper.