WATER HYGIENE AND SAFETY


takes 10 days to complete, and may take a further two days to confirm with traditional confirmation techniques. Rapid confirmation techniques can remove the confirmation step through protein identification, such as MALDI-TOF. The ISO states that samples must be read at several points throughout the 10 days; most laboratories do this around days 4 and 7, before a final read on day 10. Any of these reads can result in a presumptive positive. This is where Legionella bacteria are suspected of being present on the agar plate. The laboratory will run its confirmation process to confirm a colony is the suspect bacteria, in this case Legionella. This confirmation can be rapid in the case of MALDI-TOF, or it can take up to two days using the traditional approach.


The laboratory will normally send a positive notification once the result is confirmed. At this point the laboratory has confirmed that the bacteria present on the culture plate are Legionella; they may also offer you an early count in colony-forming units (cfu) in the volume of sample submitted; normally a litre; giving results in cfu/L. If this confirmation is sent on an interim read, on days 4 or 7 in the example above, then you should be aware that the count could increase in the final read.


What does the LCA expect of registered members when a positive result is confirmed?


This section relates to any species of Legionella. The Health and Safety Executive and Department of Health guidance documents do not discriminate between serogroups or species of Legionella, and nor should your actions. The LCA would expect that any registered member would have a procedure to notify its client, log the result, track actions, note resolution, and close out a positive Legionella result. Each of those stages may have numerous steps.


Notifying a positive Legionella result The result should be notified to your client at the earliest opportunity, and this includes interim positive results. Where you are registered with the LCA, under section 7.4 the notification must include an interpretation of what the results mean, and advice on what to do to resolve the underlying issue. HTM 04-01 Part B gives good advice on how to interpret positive Legionella results in healthcare settings. For other settings, the general principles are the same, but the susceptibility of the population is likely to be lower. The interpretation of sample results will follow directly from a well-designed sample plan. A sample is a small part designed to represent a larger population. In this case you’ve selected small volumes of water to represent the risk in the water system as a whole. When addressing


50 Health Estate Journal September 2021 Taking a sample for Legionella.


issues, you must consider the whole system, and not just the sample locations if the results indicate widespread contamination.


Interpreting positive results Positive results from pre-flush samples at limited locations, with no positive results on any post-flush samples, could be interpreted as localised colonisation at outlets only, with actions recommended to address outlets such as localised disinfection, flushing, etc. Widespread positive results from pre-flush samples with no positive results on any post-flush samples may indicate common issues and widespread colonisation at outlets. Actions should address all outlets represented by the sampling, and not just the ones actually sampled. Widespread positive results from pre- flush samples with positive results on post-flush samples indicate system-wide issues. Actions should address the whole system with all its outlets, not just the ones sampled.


An LCA member’s procedure should detail how they tell their client the information (is it an email, a phone call, a form to fill out and send, etc.), and how they arrive at the advice they give. This procedure should then be followed in practice, and at audit the LCA will expect to see an audit trail for each positive result.


Addressing the root cause For Legionella to grow there must be suitable conditions, and there will be a root cause for these conditions. Actions following positive samples must address the root cause, rather than just the symptom. Common factors include: n Stagnation; areas being less used than previously thought.


n Thermal gain/loss, meaning systems normally reside at growth temperature


despite running at below 20˚C after two minutes, or above 50˚C within one minute.


n Stagnation due to failed hot water system circulation.


n Unknown deadlegs. n Materials or contamination in the system that support growth.


Reviewing the assessment of the risk, and addressing whatever is found, must be the primary recommendation, but unless very simple and straightforward to achieve, there should also be interim recommendations. Processes like taking outlets out of use, fitting point-of-use Legionella filters, or carrying out cleaning and disinfection work, are typical interim actions that address the immediate symptoms, but may not address the root cause. Recommended actions should be appropriate for the results. This can be a difficult balance to strike, but if the results indicate limited localised issues, take limited localised action, whereas if the results indicate more widespread issues, take system-level actions.


Logging and tracking a positive Legionella result The result should be logged on your system as a non-conformance, like any other loss of control non-conformance. Your interpretation, recommended actions, and the reasons behind these, should also be logged and recorded as part of the process.


Once the result has been logged in your system, the consequent actions need to be tracked and auditable. If actions are required by you or your customer, then ensure that these are undertaken, and recorded in your logging process.


Resolve the positive result and ‘close out’


Once the root cause has been identified and resolved this action should be noted on your log, and the positive result closed out. In many cases it is normal to carry out follow-up sampling after remedial action to verify success.


Summary Sampling for Legionella can be an important part of the monitoring of control measures in a written scheme, and competent interpretation of positive results is essential. Appropriate planning, technique, and interpretation, are vital to ensure that the information obtained by sampling is valid and useful. The LCA requires members to have in place management procedures that detail how samples are planned, carried out, non-conformances logged and dealt with, and actions closed out, including communication with clients. Please see the LCA service delivery standard for further details on what the LCA requires of its members.


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