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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