In hospitals, bacteria such as Pseudomonas aeruginosa and Legionella can contaminate water systems and potentially lead to serious infections in vulnerable patients. Hospital facilities managers must test water systems regularly to ensure any contamination is detected as early as possible, so that remedial action can be initiated before any risk to patient safety arises.
The IDEXX Pseudalert® and Legiolert® methods provide rapid, accurate testing options for Pseudomonas aeruginosa and Legionella pneumophila respectively. With minimal staff training and capital expense, the tests can be carried out on-site at a hospital. A user can process a sample for each test in a minute, while the interpretation of results is as simple as observing fluorescence or a colour change after incubation.
Carrying out the test on-site reduces delays and allows for more frequent and rapid routine detection and trend analysis, empowering facilities managers to take control of sampling, analysis and detection, thereby reducing risk to patient safety.
Case Study: Guy’s and St Thomas’ NHS Foundation Trust, London, UK
With a water system including 10,000 thermostatic mixing valves and approximately 18,000 outlets, coordinating testing and remedial work against waterborne microbiological contamination is essential to keep the system at Guy’s and St Thomas’ fully operational.
When a Pseudomonas aeruginosa contamination problem developed a few years ago, the trust was using a specialised external water contractor. The need to coordinate sampling and send samples to an external laboratory made the process time consuming, and there was always the risk that issues would develop while waiting for results.
The trust began to work with IDEXX, and following the incident, adopted Pseudalert to identify and locate any issues with Pseudomonas aeruginosa. Now, samples are collected and processed by the estates team – which ensures that all the correct parameters are followed throughout the process – and tested with the IDEXX system on-site. Confirmed results are available within 24 hours, as opposed to the week-long turnaround that was common using contractors and an external laboratory.
“Using the IDEXX tests puts us in control of the whole process, and we can ensure that each stage is conducted correctly, samples are being taken correctly, and maintained within the correct temperature range throughout the transit stages – from sample point to laboratory.” Louise Clark, Associate Director of Engineering at Essentia, part of Guy’s and St Thomas’ NHS Foundation Trust.
During the Covid-19 pandemic, the trust faced a potentially major Legionella issue in a non-patient area, where outlet use had dropped due to reduced staffing, despite the introduction of enhanced flushing procedures throughout the estate wherever lower utilisation had been identified. The restrictions in place because of the pandemic meant that there were challenges in coordinating external contractors to sample and test water. The trust turned to IDEXX for advice and assistance based on their experience with the benefits of the Pseudalert method.
The trust trialled the use of the IDEXX Legiolert test to see if the problems could be identified and resolved more effectively than they were with spread plate tests, which take up to two weeks to confirm the presence of Legionella. The Legiolert method delivers confirmed results for the presence of Legionella pneumophila – the principle causative agent of Legionnaires’ disease – within seven days.
Samples were run using both the Legiolert method and spread plate method to determine whether there was correlation between the results. The comparison was very favourable towards Legiolert, which allowed the estates team to implement its use to quickly pinpoint contamination issues, undertake rapid remedial actions and check their effectiveness.
After this initial trial, the Guy’s and St Thomas’ estates team installed an on-site Legiolert testing system and continue to use both the Pseudalert and Legiolert methods. Having reviewed its internal arrangements and procedures, the trust recognised the importance of continual monitoring and testing, and amended its standard operating procedures to include the use of IDEXX rapid testing methods alongside accredited procedures to support and understand the extent and impact of any contamination and remedial actions.
Legiolert is used to support the testing for Legionella alongside testing by external laboratories. For Legionella risk management, the Approved Code of Practice (ACoP), “The control of legionella bacteria in water systems (L8)”, takes the relevant parts of regulations and provides a helpful guidance document and is supported by the guidance document, HSG274 Parts 1, 2 and 3, “Legionnaires’ disease: Technical guidance”, published by the HSE.
The estates team sees the benefits of on-site testing when evaluating areas of low usage, where counts can be high. Legiolert can be used to monitor the outlets here, giving an early indication and enabling quicker remedial action. Where there is suspected Legionella contamination, three clear results are needed to remove point-of-use-filters, so Legiolert offers an early indication of any bacterial growth, speeding up the process and reducing costs.
The guidance on testing for Pseudomonas aeruginosa in Health Technical Memorandum 04-01 (HTM 04-01) Addendum: Pseudomonas aeruginosa – advice for augmented care units, does not specify testing by an external laboratory, and the trust’s longer-term use of the method gives it confidence in the test’s value and accuracy. In 2018, Pseudalert was accepted as the worldwide standard ISO 16266-2 for the detection of Pseudomonas aeruginosa in water, and in 2021 as the European standard EN ISO 16266-2. It is also approved within the Standing Committee of Analysts (SCA) “Blue Book” publication, “The Microbiology of Drinking Water (2015) – Part 8 – Methods for the isolation and enumeration of Aeromonas and Pseudomonas aeruginosa.” Legiolert is also specified as a recommended method in the SCA “blue book” publication “The determination of Legionella bacteria in waters and other environmental samples (2020) – Part 2 – Culture Methods for their detection and enumeration”, and was also published by ASTM International as “ASTM D8429-21: Standard Test Method for Legionella pneumophila in Water Samples Using Legiolert”.
“We believe that the system we have adopted, which uses testing conducted in UKAS-accredited labs. supported by our own in-house testing, gives us real advantages in the way we test for the bacteria and what we do when we find them. Hospitals are there to make people better, rather than to give them another infection. Therefore, should there be a risk of Pseudomonas aeruginosa or Legionella pneumophila, the way we monitor and test our systems in-house with the support of IDEXX methodology is really useful. Using this testing technology allows us to implement and confirm remedial actions in the shortest possible timeframe, minimising any impact on patient care.” Louise Clark.
For more information on how IDEXX can support on-site testing, click here.
IDEXX Water UK – Units 1B and 1C, Newmarket Business Park, Studlands Park Avenue, Newmarket, Suffolk CB8 7ER.
T: 01638 676800
The IDEXX On-Site Testing System
The IDEXX on-site water testing system equipment is pictured and includes, from left to right: an IDEXX Sealer PLUS and Quanti-Tray inserts, Pseudalert reagent, vessel rack and sample bottles, an IDEXX ultraviolet light with viewing box, Quanti-Trays, and an incubator.
Unlike traditional culture methods, Pseudalert and Legiolert use a bacterial enzyme detection technology to identify the presence of Pseudomonas aeruginosa and Legionella pneumophila respectively.
The tests consists of a powder reagent, which is added to a standard 100ml water sample, and then incubated at 38°C for either 24 hours in the case of Pseudalert, or 7 days for Legiolert at 39°C. Unlike traditional techniques, no media preparation is necessary and the non-toxic reagents come in ready-to-use, unit-dosed packaging. Positive contamination is indicated by fluorescence under ultraviolet light for Pseudalert, and by a colour change to brown for Legiolert.
Quantification of bacterial contamination is undertaken using the IDEXX Quanti-Tray®, which is a specifically designed, multi-well plate to enumerate bacteria in water samples. Once the water sample is collected, the pre-dosed powder is added to the sample container, then agitated and poured in to the Quanti-Tray, which is then sealed to create a number of discrete cells where the reaction takes place when incubated. After incubation, the number of positive wells are counted, and this is used to determine the level of contamination using the most probable number, or MPN, method.