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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