Whilst ‘temperature’ is the accepted ‘traditional method of control’ for controlling waterborne bacteria such as Legionella within healthcare water distribution systems (ACoP L8, HSG274 Part 2 - paragraph 2.6 and HTM04-01 Part B - paragraph 4.7), there are now many methods which can be employed to suitably disinfect these systems (chemical, physical as well as thermal) thus mitigating the risk of; local or system-wide colonisation and associated infection and disease – when patients come into contact with waterborne pathogens.
Strategies to control waterborne pathogens
It’s widely accepted that the sufficient turnover of water (including the flushing of infrequently used outlets) and adherence to the prescribed hot and cold water temperatures (detailed in HSG274 Part 2 – paragraph 2.6 and Appendix 2:2 as well as HTM 04-01 Part B, paragraphs; 4.7 & 5.11) predominate the water treatment strategies which can be employed to control waterborne pathogens such as Legionella and Pseudomonas within health estates. As firstly; the movement or velocity of water whilst under sufficient pressure will create a ‘shearing’ force within the system which seldom provides planktonic (free floating) bacterial cells with the opportunity to settle and adhere to the inner surface of pipe work (often resulting in the early stages of biofilm formation (conditioning)). As such, these planktonic cells (ubiquitous in the environment) and system-wide particulate are moved through the water system and harmlessly flushed to drain. Secondly; waterborne pathogens such as Legionella typically grow or multiply between the temperatures of 20-45°C. Therefore, provided that the cold water is ‘cold’ (≤20°C) and the hot water is ‘hot’ (stored at 60°C and returned at ≥50°C), both temperature control and the sufficient turnover of water remain very effective methods for controlling the bacterial load and associated waterborne pathogens in health estates.
Mitigate the risk of colonisation
Eliminating the stagnation of water is imperative for mitigating the risk of biofilm formation - both within the system (as commented above) as well as within the asset (shower or tap). Therefore, as well as ensuring; an outlet is in regular use and flushing – where appropriate, it’s also prudent to ensure that these outlets are suitably cleaned and free from scale - which may also harbour harmful aquatic microbes. The adequate cleaning of assets will help to mitigate the risk of colonisation from biofilm bacteria such as Pseudomonas, which is an opportunistic microorganism (awaiting a breach in the host defences) that frequently colonises infrequently used or inadequately maintained outlets. Pseudomonas is considered a ‘primary infecting organism’ in that by virtue of its biofilm-forming nature, will provide a suitable environment for other (sometimes pathogenic) organisms to grow within, such as Legionella (considered a secondary infecting organism). Legionella bacteria will rarely survive (in planktonic form) outside of biofilm or a protozoan host, therefore in ensuring that outlets are free from scale (also considered a biofilm) in as far as what’s reasonable and practicable, this will help to mitigate the risk of individuals contracting waterborne infection. In this sense; control the ‘home’ in which aquatic bacteria propagate and proliferate and control the risk…
Scale formation will vary considerably based on geographic location of the estate, so for that reason, consideration must be given to the ‘natural chemistry’ of the water system being managed and how that may impact on cleaning frequency, as ‘hard water’ areas (those with an abundance of calcium carbonate) will undoubtedly require greater vigilance (with regards to scale formation…) than ‘soft water’ areas due to their propensity to produce more scale. For this reason ‘periodic’ cleaning is advised in HTM 04-01, whereby frequency of cleaning is ‘site/system specific’.
Mitigate risk of cross-contamination
The importance of adequately cleaning outlets whilst ensuring that assets are not misused (WHB are used for hand washing…) are key considerations in HTM 04-01, whereby guidance in this regard is given specifically – to mitigate the risk of augmented care patients from acquiring Pseudomonas aeruginosa. Moreover, the focus of this guidance is to not only ensure that assets are suitably cleaned, but to also mitigate the risk of cross-contamination of assets (WHB & taps) with waterborne bacteria such as Pseudomonas. With this in mind; it’s noteworthy that whilst it’s accepted that tap and shower outlets may be a reservoir for contamination for bacteria such as Pseudomonas, one must also consider that Pseudomonas bacteria are ubiquitous. Therefore, just because an outlet becomes colonised with these bacteria - the associated water system doesn’t always represent the cause of the problem especially when non-conformances have been observed from either a cleaning or use (misuse…) perspective.
The principles behind ensuring that water is wholesome and microbiologically safe are quite straightforward but ongoing compliance to these principles takes time, consideration and buy-in from a number of key stakeholders from; infection control teams, microbiology, estates, health & safety, projects & design and most certainly facilities. As such, the formation of water safety groups (WSG) are multidisciplinary groups with responsibility for ensuring the safety and quality of water. In addition, these groups also welcome professional support from Authorising Engineers – to provide further advice and support with shaping water safety plans and policies - to help ensure that all appropriate operational and managerial water safety concerns have been considered and that the organisation being advised – understands its health and safety obligations (in this regard) and how to comply with them.
Editors Note: The information provided in this blog is correct at date of original publication - October 2017.
© Water Hygiene Centre 2019