What’s going on with surface disinfection in dental settings?


An interesting new article reviews the history and state-of-the-art for surface disinfection in dentistry settings. Historically, aerosols and sprays were the most common approaches to the delivery of disinfectants in dentistry. However, due to occupational exposure concerns, disinfectant wipes are quickly becoming the most common method for surface disinfection in dental settings.

The article spans space and time, beginning with acidic rinses used by ancient Egyptians in 3000 BC, and ending with a review of current disinfection approaches. The article provides a helpful list of chemicals currently used for surface disinfection in dentistry settings.  Quaternary-ammonium based disinfectants the most common disinfectant, and wipes are becoming the most common mode of delivery. The article also highlights some of the unique challenges of dentistry settings, with a need for local sterilisation of some items and the associated surface hygiene requirements, x-ray equipment, rapid service user throughput, and limited availability of support staff.

Finally, the article provides some good practice recommendations for surface hygiene in dental settings. These include the need for a local infection control and environmental hygiene policy, a recommendation in favour of using disinfectant wipes, and recommendations around best-practice use of wipes in dental settings along with a visualisation of common high-touch surfaces to target.

Dentistry often includes invasive procedures and infections can be serious and difficult to treat. So it’s vital that the dental environment is kept clean and safe to prevent the transmission of microorganisms that can cause infections.

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Celebrating world hand hygiene day

As we come towards 5th May, it’s time to celebrate global hand hygiene day! This year, the theme for the WHO’s campaign is ‘Clean care for all – it’s in your hands’.

The WHO team in Geneva have published editorials in a range of journals (including one here in Infection Control and Hospital Epidemiology) outlining the details of the campaign. The campaign includes individual calls to action for different staff groups. This is a good message: regardless of your professional background or role, hand hygiene is in your hands! The campaign and also launches a Global Survey on Hand Hygiene (details here).

The idea of ‘Clean care for all’ is broader than just hand hygiene – and encompasses the cleaning and disinfection of surfaces and medical devices in what is a ‘multi-modal’ approach to infection prevention. The transmission of pathogenic micro-organisms between patients occurs through a complex network of vectors and fomites. If we are to prevent the transmission of pathogens that cause HCAI in hospitals, it’s no good just focussing on hand hygiene – otherwise the organisms will ‘choose’ an alternative route (see the Diagram below)!

   Diagram: Dynamic transmission routes of microorganisms that can cause HCAI

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The importance of standardised testing of disinfectants for hospitals

We blogged last time on the first in a series of articles in the Journal of Infection Prevention about disinfection in healthcare. The first part in the series argues for routine disinfection of the healthcare environment. This second instalment describes the importance of standardised testing of disinfectants for hospitals.

The authors describe the bewildering choice of disinfectant chemistries and formulations that are now available for disinfecting healthcare surfaces. Infection Prevention and Control experts have a key role to play in ensuring that the most appropriate range of disinfectants are available to hospital cleaning teams. The key property of a disinfectant is its ability to kill microorganisms. Therefore, a crucial step in the process of selecting an appropriate disinfectant is ensuring that it has the required level and range of biocidal activity through standardised laboratory testing.

The article describes the family of European testing standards (EN standards) that are currently available, including both suspension testing methods, which test the ability of a disinfectant to kill microorganisms in a liquid suspension, and surface/carrier testing methods, which test the ability of a disinfectant to kill micro-organisms dried onto a surface. Key considerations when considering testing standard include:

  • Disinfectant neutralisation. If this is not done properly, efficacy will be over-estimated.
  • The level of soiling. Various different approaches can be taken to replicate soiling, often using proteins. This should reflect in-use conditions to the extent possible.
  • Selection of test organisms. For example, it’s no good only testing against vegetative bacteria if you need a sporicidal disinfectant!
  • Contact times. Unrealistically long contact times may well not provide a meaningful assessment of the disinfectant that is being tested.
  • Pass criteria. Most EN standards require a greater-than-or-equal-to 5-log reduction, but some standards have a lower pass criteria for practical reasons.
  • On a more practical level, it is vital to perform disinfectant testing in accredited laboratories who are experienced at performing this sort of testing. Otherwise, common pitfalls can occur and efficacy can be over-estimated. Commonly, disinfectant neutralisation is not performed adequately, meaning that the actual contact time is longer than the intended contact time and the efficacy of the disinfectant is over-estimated. For example, many ‘sporicidal’ disinfectants that are on the market do not exhibit meaningful sporicial activity when tested using appropriate laboratory methods. Therefore, when reviewing a disinfectant for use in a hospital, it is wise to ask the following questions:

  • Is it biologically plausible that this disinfectant chemistry will have the level and range of biocidal activity that is being claimed? For example, we know that only a relatively few disinfectant chemistries can have meaningful sporicidal activity.
  • Was an appropriate testing standard used? For example, a suspension test (such as EN 13727:2012) does not provide good evidence that a disinfectant will be active against bacteria dried onto surfaces; instead, a carrier test (such as EN 13697:2015) should be used.
  • Were the tests performed in an accredited, experienced laboratory that has produced a report with a sufficient level of detail? If not, biocidal efficacy could be over-estimated.
  • Biocidal activity is a vital factor in selecting an appropriate disinfectant. However, other factors are also crucial when selecting the right disinfectant, including the mode of application, environmental impact, potential occupational exposure issues, and formulation. These factors must be considered together when selecting the most appropriate hospital disinfectant. 

     

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    Arguing for routine disinfection of the healthcare environment



    A new review in the Journal of Infection Prevention by Dr Evonne Curran and colleagues sets out the arguments for and against the routine use of disinfectants in the healthcare environment. The review dispels some of the common arguments used against the routine use of disinfectants in the healthcare environment, and presents a novel risk-based scheme for deciding when to use detergent only for cleaning surface in the healthcare environment (which is not very often!).

    Historically, the use of detergent cleaning only without the use of a chemical disinfectant has been the favoured model for cleaning the healthcare environment in the UK (whilst other countries have historically taken a more disinfectant-centric approach). However, we now know that detergent cleaning only does not reliably eliminate pathogenic micro-organisms from surfaces, and can inadvertently spread pathogens between surfaces. Therefore, routine use of disinfectants in the healthcare environment is becoming more common.

    This review article examines the common arguments against the routine use of disinfectants in the healthcare environment:

  • “Recolonisation happens too quickly”. Whilst recontamination of surfaces in the environment can happen quickly, the use of disinfectants should be targeted to the surfaces and scenarios where surface contamination is involved in transmission, for example, at the time of discharge, and when patients are not (yet) known to be colonised or infected with a pathogen.
  • “Disinfectants damage the environment”. We know that some chemical disinfectants damage the environment (e.g. chlorine) but the risk profile of other disinfectants are considerably better (especially the peroxygens such as peracetic acid and hydrogen peroxide, which break down into environmentally-friendly by-products). The risk of environmental impact from disinfectants is mitigate by appropriate use and disposal, and detergents are not without their own environmental impact!
  • “Disinfectants present an occupational hazard.” This is true, again, for some disinfectants more than for others; this is especially a concern for chlorine-based disinfectants. However, the risk of occupational exposure can be managed out through the appropriate use of personal protective equipment.
  • “Disinfectants themselves can become contaminated and present an outbreak risk.” This is a risk for certain application modes of certain disinfectants. However, it is much more of a risk for detergents, which don’t kill microbes! Also, the use of disinfectant wipes eliminates this risk.
  • “Disinfectants are costlier than detergents”. Taking account of all factors, including the impact of reduced HCAI, and investment in disinfectants is likely to be cost neutral or even cost saving. Whilst the true cost of HCAI can be difficult to measure, it only takes a small number of HCAI events to tip the financial scales towards using disinfectants.
  • “Micro-organisms could develop tolerance and resistance such that disinfectant-resistant organisms emerge”. If disinfectants are used at their in-use concentrations, clinically meaningful disinfectant resistance is unlikely to emerge. Indeed, common disinfection chemistries (such as quaternary ammonium compounds, peroxygens, and chlorine) have been in global use for many years and resistance to these chemical disinfectants has not emerged.
  • The article also makes a case that the traditional approach to risk assessment for when to use a disinfectant and when to use a detergent needs to be re-evaluated in light of modern healthcare, restricting the use of detergent-only cleaning to settings outside of the patient zone when no medical equipment is around.

    In summary, the use of disinfectants for cleaning and disinfecting the healthcare environment is evidence based, maximises patient safety, and is likely to be at least cost-neutral if not cost-saving.

     

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    The risk of keyboard contamination

    Computer keyboards are a potential contamination risk in the hospital setting. A new systematic review of the literature concludes that computer keyboards are frequently contaminated and that more studies are required to understand the risk they pose and effective and practical methods to prevent and reduce contamination. 

    Computer equipment in hospital settings, such as keyboards, mice, and smartcard readers, frequently become contaminated with pathogens that can cause HCAI and are difficult to clean and disinfect. Furthermore, hand hygiene rarely follows contact with computer equipment in clinical settings. Since computer keyboards are handled by multiple staff groups, and since hand hygiene practice is rarely optimal, pathogenic organisms could be deposited onto keyboards by one staff member, and acquired on the hands of subsequent staff members, fuelling the spread of pathogenic organisms in hospitals.

    Improved design and disinfection of computer keyboards has been shown to reduce the level of microbial contamination, and so reduce the risk of transmission. For example, Clinell EasyClean computer keyboards, mice, and smartcard readers have been designed to simplify cleaning procedures and increase compliance.

    The review identified 75 studies including data from 2804 individual computer devices. Around one third of these studies also reported on the efficacy of disinfection methods for computer keyboards. The most common organisms found to contaminate keyboards in healthcare settings are, unsurprisingly, skin commensals. However, potential pathogens including MRSA, C. difficile, and VRE have also been identified. Disinfectant wipes were one of the methods found to be effective in tackling contamination of computer keyboards. The review concluded that more studies are required to scale the risk of computer keyboards as a potential fomite for the transmission of pathogens in healthcare settings.

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