DECONTAMINATION
hours. This means the risk of contracting coronavirus and becoming infected through contact with contaminated surfaces is high.5 In addition to the predominant modes of transmission, initial research has also identified the presence of the COVID-19 virus in the stools of confirmed cases. The virus has also been found in blood, saliva, tears, cerebrospinal fluid, and conjunctival secretions.6
Therefore, Public Health England has advised that ‘all secretions (except sweat) and excretions, including diarrhoeal stools from patients with known or possible COVID-19, should be regarded as potentially infectious.’7 The BSG recommends that a guiding principle for decontamination is that ‘any patient must be considered a potential infection risk, and each endoscope and device must be reprocessed with the same rigour following every endoscopic procedure’.8
This is a principle which is just as relevant to reprocessing in the COVID era.
Human coronaviruses and disinfection
Human coronaviruses, including SARS- CoV-2 are classified as ‘enveloped’ viruses, whereas viruses, such as rotavirus or poliovirus, are termed ‘non-enveloped’. Enveloped viruses have an envelope or outer coating that is composed of a lipid layer (fat-like substance that is water insoluble). The envelope is needed to help the virus attach to the host cell. Without the protective coating, the virus cannot cause infection. According to Public Health England:
‘As coronaviruses have a lipid envelope, a wide range of disinfectants are effective.’7 However, a 2012 study examining human coronaviruses in relation to environmental resistance and disinfectant strategies strikes a note of caution, warning that despite the accepted fragility of enveloped viruses, they are potentially capable of developing significant environmental resistance.9
Their
survival in different biological fluids such as respiratory secretions or faeces has been proved. Furthermore, some parameters seem to benefit the survival of human coronaviruses such as the stabilising effect of low temperatures and high relative humidity or the protective action of organic materials.’9 However, the scientific community is constantly learning more about human coronaviruses, how they behave and the most effective management strategies. For now, the emphasis must be on the most effective possible cleaning and disinfection procedures to minimise the risk of infection.
Efficacy vs material compatibility When selecting a detergent/disinfectant for use in a washer disinfector, the additional challenges posed by COVID-19 need to be considered. Any instruments or devices used on COVID-19 patients or patients suspected
OCTOBER 2020
of having COVID-19 should be considered particularly high risk in terms of potential cross infection. The aim of medical device decontamination should be to minimise the risk of contamination between patients, staff and procedures. It is essential that the selected chemical is compatible with the range of medical devices and surgical instruments being reprocessed, as well as with the washer disinfector. HTM 01-01 1.126 states ‘that the cleaning formulation should have no long-term effects on the components of the washer-disinfector.’ The 2018 European Society of Gastrointestinal Endoscopy guidelines make recommendations about the disinfectants used in reprocessing procedures which include coronaviruses. ‘Disinfectants used for this purpose must be bactericidal, mycobactericidal, fungicidal, and virucidal against enveloped and nonenveloped viruses.’2 According to the BSG, 2016 the ideal chemical disinfectant/detergent should include a broad antimicrobial spectrum; be rapid-acting, noncorrosive, and not harmful to the device and its parts; non-toxic to humans and the environment; and capable of being monitored for concentration and effectiveness.10
This underlines the importance of striking an optimum balance between achieving a high level of antimicrobial efficacy and ensuring material compatibility with the device(s) being reprocessed.
The potential ‘environmental resistance’ of coronaviruses will need to be carefully considered when developing disinfection strategies. One solution may appear to be to use a higher quantity and/or concentration of the antiseptic-disinfectant product and so produce a higher toxicity to the virus; or possibly to select a new detergent/ disinfectant with a stronger virucidal action. However, before making changes, material compatibility with the medical device being reprocessed and also the washer-disinfector itself must be considered.
Put simply, there is little point in switching to a harsher chemical agent which may over a relatively short period of time damage expensive medical equipment, invalidate warranties and affect processing downtime resulting in patients waiting even longer for procedures. The worst-case scenario is that the decontamination process may not be of the appropriate standard. Interestingly Public Health England recommends that ‘instruments and devices should be decontaminated in the normal manner in accordance with manufacturers’ advice’ and ‘products must be prepared and used according to the manufacturers’ instructions.7
PHE does not recommend
using a stronger or more concentrated detergent/disinfectant. The recommendations in HTM 01-06 Decontamination of Flexible Endoscopes highlight the need to find a balance between efficacy and compatibility. The chemical additives used in the decontamination process ‘must be compatible with the materials of which the washer- disinfector is constructed and also with the items to be processed.’
These recommendations are similar to those in HTM 01-01 Management and decontamination of surgical instruments, which specifies the need for the selected cleaning formulations to ‘have no long-term effects on the components of the washer- disinfector.’ This is because they can be adsorbed onto surfaces of the washer- disinfector and may then be carried over into subsequent stages of the process. e.g. phenolic compounds used in detergents and disinfectants might cause material changes in rubber and plastics, while the anodic coating on the surface of anodized aluminium is removed by strongly acid or strongly alkaline compounds. Most washer-disinfectors are composed
partly or wholly of stainless steel; meaning that the detergent and other chemical additives used, should have a low chloride content to minimise the risk of corrosion.
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