- 11 October 2018
Dr Rosalind Stanwell-Smith, Deputy Editor of Perspectives in Public Health, reports from the conference 'Water Safety – it’s choice not chance!'
This conference focused on the implementation of Water Safety Plans (WSPs) in hospitals, covering a range of water topics from adhesion in biofilms to ‘wipes stuck in pipes’, in addition to updates on microbiology, regulations and how to develop a Water Safety Group (WSG).
A good WSP can change the culture of an organisation, but only if there is more than ‘tick-box’ compliance and support for innovation. There may be a lack of demand for change, with staff simply putting up with poor tap and sink design. Also, finding the best possible solution involves tailoring training to the particular environment, appreciating the range of chemical as well as microbiological hazards and working on multiple-barrier approaches.
Patient stays have shortened, but with more at-risk seriously ill patients: the WSP should incorporate a whole system framework that covers all the uses of water within the hospital including: food preparation, heating, cleaning, irrigation and water features, as well as the more obvious uses. Many water hygiene challenges can be traced to poor design, including corrosion, scale, leaching of nutrients and potential build-up of hazards within the system. The associated infections may result in legal fees, long-term effects and mostly preventable deaths: a US survey of Pseudomonas aeruginosa infections estimated around 1400 fatalities annually from waterborne pneumonia.
Validation and verification are important WSP stages. Verification includes assessing if the water system meets the design specification, for example in storage, heating, biocide dosing, pipework, components and outlets. Validation assesses if the system meets operational needs in terms of water volume, temperature, control of scalding risks and whether outlets are in the right place for clinical use, staff and the public. Monitoring then checks whether a system continues to operate safely.
The risk assessment should be the basis of what is measured – organisms, sentinel outlets and key risk usage areas - always considering the reliability of the information in terms of equipment and good sampling technique. Augmented care units are an obvious high risk for patient safety. It is important to be realistic in terms of monitoring frequency and for detecting changes in risk. A one-off sample for P. aeruginosa, for example, may give false reassurance if negative.
Monitoring is not just sampling: there should be a check on cleaning procedures, including when it is done and if it follows a ‘top down’ clean to dirty sequence. Since the ideal disinfectant does not exist, the best means of keeping a system clean is to stop the dirt getting in. Resistance to biocides means that a multi-barrier approach is essential. Keeping the system clean includes minimising blockages and stagnated water in parts of the system: an average of 391 blocked sinks, toilets or sluices occurred per hospital each year from 2005 to 2010. Biofilm formation can be minimised by attention to pipe materials, controlling potential organisms and avoiding stasis. The shedding from biofilms contributes 1% of the bio-burden in the water system.
The highest risk area is in the system periphery or in under-used facilities such as showers. The risk assessment should include the design of the taps and whether there is sufficient ‘activity space’ to avoid contaminating the tap or sensor. High background levels of contaminants may mean that those causing infection can be missed and sampling needs to be well planned. A pre-flush sample should be taken after 5 hours of non-use, waiting for the tap to run for at least 2 minutes before taking a post-flush sample.
One of the aims of monitoring is to identify opportunistic premise plumbing pathogens (OPPPs). This involves considering the location and timing of a sample to obtain the most representative results. Sampling technique differs for different organisms – and the laboratory needs to receive pertinent information on each sample. Microbiological culture is still the ‘gold standard’, although it is slow and the organisms may be ‘in shock’ and unrecoverable, up to 50% in the case of Legionella.
Culture may take days or even weeks, which is why rapid testing is so useful. Its advantages over culture include higher sensitivity, detection of viable but non-culturable cells (VBNC) and point of use testing. Real-time polymerase chain reaction (RT-PCR) can produce results in around 3 hours and a particularly useful feature is its good negative predictive value – i.e. to detect that an organism such as Legionella is absent. Enzyme-based kits are helpful in monitoring P.aeruginosa, producing a fluorescent signal if the organism is present.
One of the fastest rapid tests is the immuno-magnetic method, which takes about an hour to show a colour change, allowing the number of e.g. Legionellae to be quantified. For all these tests it is essential to check validation, peer-reviewed evidence, cost and, not least, how the end user will interpret the results. The laboratory has a responsibility in making sure there is good understanding of new tests, including the limitations.
An outbreak of mycobacterial infections following cardiac surgery illustrated the value of surveillance and investigation. The infections had occurred over 7 years in 11 different NHS hospitals. All the hospitals had used heater cooler units (HCUs) during surgery: testing revealed mycobacteria and very high total viable counts of other organisms, notably Pseudomonas and Stenotrophomonas. These were present both inside the machine and outside, where a fan facilitated aerosol release of the organisms. Control involved enhanced decontamination, changes in how the HCU was used and microbiological monitoring.
The regulatory approach is underpinned by evidence and science, and in the last 15 years the Health and Safety Executive has focused more on health outcomes, with health based legislation such as regarding lead, noise and asbestos. While neither WSPs nor WSGs are legal requirements, they are considered good practice, fitting with a holistic approach to risk.
Competence of those managing the risks continues to be a concern, with a lack of training identified in 27% of those responsible for evaporative cooling towers. Apart from emphasising the need for a WSP and WSG in every hospital, the take home thoughts were about training, considering the uses of water as a whole, encouraging innovation and staff feedback and how to monitor intelligently. And above all, remember to treat the risk, not the sample!