INF ECT ION PR EVENT ION & CONT ROL
to ensure the highest infection prevention standards are maintained, but this may require a little research to ensure disinfectant claims are truly comparable.
Disinfectants have a variety of properties that include spectrum of activity, mode of action, and efficacy. Equally, the actual active chemicals in the disinfectants may be categorised into groups based on their chemical nature, spectrum of activity, or mode of action. Effectiveness is assessed through disinfectant efficacy testing, but a problem faced when selecting a disinfectant, is the array of different standards. This is where the EU standards have a useful role to play, although some understanding of them is required if they are to be used as the basis for disinfection selection. It is worth noting that the European approach of CEN (European Committee for Standardization) to the evaluation of disinfectants differs from that taken in North America by ASTM (American Society for Testing Materials) standards and the AOAC (Association of Official Analytical Chemists International). This does nothing to alleviate potential confusion about testing and there have been calls for agreed international test standards. However, that is outside the scope of this article.
Disinfectant standards are required for several reasons. Primarily, any company that wishes to market a product in the European Economic Area needs a CE mark which identifies that the product conforms to an accepted standard of quality. The mark stands for Conformité Européenne. By placing the CE marking on a product a manufacturer is declaring conformity with all of the legal requirements to achieve CE marking. It means that the manufacturer has checked that the product complies with all relevant essential requirements, for example health and safety requirements.
Standards for disinfectants aim to prevent manufacturers from claiming activity in a product which is not, in fact a disinfectant. For example, distilled water lyses many bacteria and therefore does have some very limited bactericidal effects, however distilled water could not be described as a disinfectant.1 Agreed standards allow for the definition of a minimum requirement for a product to be described as a disinfectant. It also
ensures that manufacturers need to be able to validate claims of bactericidal, virucidal or tuberculocidal activity. Standards give clear guidance on what is required to validate such claims.
There are a number 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 microorganisms dried onto a surface. Key considerations when considering which testing standards, a manufacturer has employed include: l Disinfectant neutralisation. If this is not performed correctly, efficacy will be over- estimated.
l The level of soiling. Various approaches can be taken to replicate soiling, often using proteins. This should reflect in-use conditions as far as is possible.
l Selection of test organisms. For example, only testing against vegetative bacteria is unhelpful if a sporicidal disinfectant is required.
l Contact times. Unrealistically long contact times may well not provide a meaningful
It is important that contact times have been correctly assessed and are adhered to, since reduced contact times are less effective against microorganisms, which may lead to a high proportion of pathogens surviving.
OCTOBER 2020
assessment of the disinfectant that is being tested.
l 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.
It is also vital that manufacturers have performed disinfectant testing in accredited laboratories, with experience at performing this type of rigorous and specific testing. If disinfectant neutralisation is not performed correctly, the actual contact time required will be longer than the published contact time which means the efficacy of the disinfectant may have been overestimated. Therefore, when reviewing a disinfectant for use in a hospital, it is worth asking:
l Is it biologically plausible that this disinfectant chemistry will have the level and range of biocidal activity that is being claimed? For example, only a relatively few disinfectant chemistries have meaningful sporicidal activity.
lWas 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.
l 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.
For hospital and medical use, there are a number of applicable standards which manufacturers of disinfectants may be
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