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Legionella Testing
See also - About Legionella and Legionnaires Disease
Emu Ltd provides specialist survey, laboratory and consultancy services to supportorganisations involved in water quality management.
Our expertise includes laboratory testing of environmental, treated, recreational and wastewaters for microbiological indicators. We support all our laboratory testing with sampling and survey services including swimming pool sampling, bathing water investigations, pollution studies, environmental monitoring and wastewater/UV disinfection performance tests.
The combination of 14 years experience in water quality sampling and microbiological testing and stringent quality assurance credentials, is the foundation upon which the company's activities are based.
Emu is ISO 9001:2000 accredited, UKAS accredited for bacteriological sampling and testing of water, sediment and sludge, as well as being uniquely accredited for bacterial tracing work using Bacillus Globigii.
Water Quality Sampling for Legionella
Sampling for Legionella should be carried out in accordance with ISO 11731:1998 and ‘The determination of Legionella bacteria in waters and other environmental samples (2005) – Part 1 – Rationale of surveying and sampling’ Environment Agency.
Emu Ltd have maintained UKAS accreditation for bacteriological sampling procedures for the last 7 years. Strict procedures must be adhered to when sampling waters for public health testing to ensure best scientific practice and traceability.
Emu’s in-house procedures include control of the following aspects of sampling:
- Selection of representative sample points and regime
- Sampling techniques as per standardised methods
- Additional monitoring to support interpretation of results e.g. temperature
- Prevention of external / cross contamination of samples
- Use of appropriate and sterile sample containers
- Use of reagents to neutralise disinfectants during transportation of samples
- Maintenance of stringent environmental conditions during storage and transportation of samples
- Detailed sample records and labelling to ensure traceability of samples
- Analysis of samples within stringent time limits
Emu sampling staff have documented training records and undergo regular internal and external audits to ensure competency. The frequency and extent of sampling will depend on nature of the system and outcome of the risk assessment. Sampling and testing for Legionella will be required on a more regular basis in response to a suspected or known outbreak. Due to the foreseeable risk associated with cooling towers and spas these systems should be routinely sampled.
For clients undertaking their own sampling, Emu can provide appropriate sample bottles, log sheets, labels, cool boxes and packaging for return postage/delivery.
Microbiological Testing of Water Quality
Two tests are associated with microbiological monitoring for Legionella risk assessment and management.
- Aerobic Colony Counts (measures general bacteria levels)
- Detection and Enumeration of Legionella bacteria
Aerobic Colony Counts (ACC)
Also referred to as Total Viable Count, Colony Count or Heterotrophic Plate Count, this test involves counting all the bacteria that grow in 1 ml of sample incubated at a temperature of 30oC for 48 hours (cooling towers), 37oC for spas.
The test provides a count of all aerobic bacteria in the water sample and does not distinguish between different types of bacteria.
The number of aerobic bacteria in a water sample is used to indicate the overall effectiveness of the disinfection system at killing bacteria.
If conditions are suitable for the proliferation of general aerobic bacteria it is also likely that conditions will also favour the growth of Legionella.
The test can also provide trend information and an early warning system. For example, a gradual or sudden increase in the number of bacteria from week to week may indicate operational or treatment problems – enabling action before Legionella have time to proliferate.
The HSE ACOP L8 outlines limits and actions relating to aerobic colony counts for specific water systems. High results should be confirmed by repeated sampling and may require a systems review or ‘shot dose’ disinfection.
Laboratories used for the analysis of aerobic colony counts should be accredited by the United Kingdom Accreditation Service (UKAS). Emu Ltd provide UKAS accredited aerobic colony count testing. Emu Ltd participates in a monthly external proficiency scheme (LEAP), demonstrating a consistently high standard of results for water samples.
Laboratory Testing for Legionella Pneumophila
Testing for Legionella bacteria is technically difficult and requires specialist laboratory facilities.
Legionella can result in death for which persons responsible for premises may find themselves or their organisation personally liable. The selection of an appropriate laboratory to carry out your analysis is critical to demonstrate that you have implemented an adequate management system.
For valid results, testing must be carried out by a UKAS accredited laboratory which takes part in the Health Protection Agency External Proficiency Scheme for the enumeration and detection of Legionella in water samples http://www.hpa.org.uk.
Emu’s microbiology laboratory provides UKAS accredited Legionella testing in accordance with the specific requirements of the HSE ACOP L8.
There are many species of Legionella, some of which pose a risk to human health and some of which do not. The first stage of testing detects the presence of Legionella without distinguishing the actual species.
If a species of Legionella is detected it may not present a direct risk to health, however, its presence may indicate that conditions exist in the water system that are favourable for more pathogenic species.
If Legionella is found in a sample, further tests are carried out to determine the species and whether it is considered pathogenic (i.e. if it is likely to present a risk to health).
Specific tests are performed to determine the presence of species’ of greatest concern, Legionella pneumophilla serogroup 1 (which causes Legionnaires’ disease) and Legionella pneumophilla serogroups 2-14.
Legionella bacteriaare commonly found in natural water sources therefore, detection in a sample may not indicate that there is a problem. Likewise failure to detect Legionella does not mean that the bacteria is necessarily absent and that controls can be relaxed. Consistent negative test results should not be used as an alternative to implementing controls.
Test results are not always definitive and must be interpreted by technically competent persons. The laboratory should therefore provide you with regular reporting and liaison to ensure test results are reviewed and appropriate actions are taken to maintain compliance with guidelines.
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Registered Address: 1 Mill Court, The Sawmills, Durley, Southampton, Hampshire, SO32 2EJ