Testing virucidal efficacy of disinfectant laundering processes
Testing laundering processes for anti-viral (virucide) efficacy has only been carried out under in vitro conditions in the laboratory until now. At the moment, no laundering process on the market has been proven and certified as virucidal because methods for in situ testing under actual working conditions have been unavailable.
Even the lists of certified disinfectant laundering processes suited for killing or inactivating bacteria and fungal pathogens (A) and viruses (B) [lists maintained by the Robert Koch Institut (RKI), and the Disinfectant Commission of the Association for Applied Hygiene, (Verbund für Angewandte Hygiene e.V., (VAH)] are based on in-vitro tests.
The Institute for Hygiene and Biotechnology (IHB) at Hohenstein has developed a virus bioindicator that will make possible in situ testing of laundering processes for virucidal efficacy [data published in Hygiene und Medizin, (June edition)]. This is a new approach to testing of disinfecting laundry processes
on virucidal efficacy in practice.
The current statistics for cases of viral disease indicate the need for in situ testing is indisputable. Take, for example, gastro-intestinal viral infections – in particular, those caused by noroviruses (NoVs) – that are constantly increasing in number in Germany. Hardest hit by these infections are social and health care institutions, such as hospitals, homes for the elderly and nursing care homes.
Human noroviruses are very resistant and efforts to grow NoV cultures under laboratory conditions have been unsuccessful so far. As a result, investigations of disinfectant efficacy up to now have been based primarily on the results of tests using viruses that are structurally similar. A virus that affects bacteria, the bacteriophage MS2, has currently been accepted as a suitable surrogate for NoVs. Researchers at the Institute for Hygiene and Biotechnology have used MS2 in their development of a viral bioindicator.
As a general practice, small textile cotton swatches contaminated with bacteria, known as bioindicators, are used to test the bactericidal effect of processes or agents. Using a similar method, the scientists at Hohenstein applied MS2 bacteriophages (as a pathogen similar to norovirus) to small cotton swatches and laundered them as they would be cleaned in situ. A disinfectant listed as a virucide was used in a low temperature (40°C) laundering process during which thermal deactivation of the virus could not be expected as a matter of course.
In order to simulate realistic processing conditions for laundry at homes for the elderly and care homes, the virus was introduced into organic, artificial faecal material that was used to simulate soiling for test purposes. Used in this form, the bacteriophages met the standard requirements for use as a test virus and could be applied successfully to evaluating the listed low-temperature laundering process.
In addition, the Institute for Hygiene and Biotechnology carried out further, comprehensive, analyses of cultivability, proof of specificity, stability and ability to disinfect. These emphasise the practicality of using the MS2 bacteriophage to simulate NoVs.
The IHB's experiments demonstrate bacteriophages such as MS2 are suitable viral bioindicators for the purposes of testing and demonstrating the virucidal efficacy of laundering processes under conditions similar to those in the field.