Legionella Detection and Identification Methods
Legionella is a pathogenic bacteria responsible for causing Legionnaires’ disease, a serious illness similar to pneumonia. In the natural environment, Legionella lives within in freshwater environments like lakes and streams and poses little threat. In human-made water systems, however, Legionella can rapidly grow out of control, reproducing to the point that it poses a serious health risk.
Legionella can cause illness when people inhale small water droplets (or aerosols) containing the bacteria. Once inhaled, Legionella attacks the lungs, which can result in Legionnaires’ disease as well as less serious diseases, including Pontiac fever and Pittsburgh pneumonia. The symptoms of Legionnaires’ disease are severe, including a cough, shortness of breath, fever, muscle pain and headaches.2 It carries around a 10% risk of death.3
Controlling Sources of Legionella
Many types of water systems, including swimming pools, showers, hot water tanks, ice-making machines and fountains are susceptible to Legionella formation.
However, Legionella is particularly associated with cooling towers, which are industrial heat-rejection systems which use water as a coolant. Cooling towers act ideal breeding ground for Legionella bacteria: they provide a warm, moist environment where the bacteria can easily reproduce.
This makes cooling towers one of the most common sources of Legionnaires’ disease outbreaks; and many government agencies, including the CDC, and trade organizations have developed guidelines specifically to control the proliferation of Legionella within these systems.4,5
Given the significant risks associated with Legionella proliferation, it’s crucial that efforts are made to reduce the risk of Legionella growth and spread within at-risk water systems. This is achieved by maintaining water systems, implementing disinfection protocols and controls for Legionella and, crucially, routine testing for Legionella. In the USA, and many other countries, employers and facility operators have legal responsibilities to identify and assess sources of Legionella.
The primary method of controlling Legionella in water systems is to keep water moving. Good system design – ensuring that pipework doesn’t contain dead-ends, for example – is crucial. Systems should also be flushed and de-scaled regularly to prevent Legionella from multiplying.
Chlorine also plays an important role in suppressing Legionella.6–8 For example, municipal drinking water supplies are typically chlorinated using chlorine dioxide gas. Chlorine residual (the amount of free chlorine present in water) is closely correlated with populations of Legionella and other bacteria – consequently, chlorine analysis is important in verifying the safety of drinking water supplies and other water systems.
The Importance of Legionella Testing
Traditional Legionella detection methods involve collecting a sample and sending it to a specialized lab where the sample is developed and analyzed for the presence of Legionella bacteria. This means that getting results can take as many as 14 days – which is a long time to not have a good understanding of legionella activity with a water system (especially if an outbreak is expected). And the results tell you what the levels were – when the test was taken – not what is “now.”
There are approximately 50 different species within the Legionella genus. Several of these can cause infections in people, however worldwide over 90% of infections are caused by a single species: Legionella pneumophila. The particular “serogroup 1” of pneumophila causes the vast majority (>80%) of all cases, and is implicated in virtually all major outbreaks.
Lovibond® offers the world’s fastest Legionella testing kits to suit any industrial or field-testing application – that specifically detects Legionella pneumophila serogroup 1.
Different versions of the test kit are available for collecting samples from a variety of sources – or to enhance the detection limit:
- Field Test Kit – Our most popular kit offers reliable, accurate, and fast testing without the need for reagents or interpretation of results, get results in just 25 minutes.
- Industrial Test Kit – Ideal for collecting samples from shower heads, taps or other sample point fittings. This kit also uses hollow fiber filtration modules to increase the sensitivity of testing.
- Swab Test Kit – Detect legionella directly where it grows: in biofilms. This kit contains sterile cotton swabs for collecting samples from inside pipes or other surfaces where biofilms form.
- Risk Assessment Kit: Ideal for first time users or those trying to develop a testing protocol for a facility. It provides supplies for collecting a filtered sample (Industrial Test Kit) or for taking a swab (Biofilm Test Kit)
References and Further Reading
1. Legionnaires Disease Cause and Spread | CDC. https://www.cdc.gov/legionella/about/causes-transmission.html (2021).
2. Legionnaires Disease Signs and Symptoms | CDC. https://www.cdc.gov/legionella/about/signs-symptoms.html (2021).
3. Legionnaires Disease Diagnosis and Treatment | CDC. https://www.cdc.gov/legionella/about/diagnosis.html (2021).
4. García-Fulgueiras, A. et al. Legionnaires’ Disease Outbreak in Murcia, Spain. Emerg Infect Dis 9, 915–921 (2003).
5. Controlling Legionella in Cooling Towers | CDC. https://www.cdc.gov/legionella/wmp/control-toolkit/cooling-towers.html (2021).
6. Kuchta, J. M., States, S. J., McNamara, A. M., Wadowsky, R. M. & Yee, R. B. Susceptibility of Legionella pneumophila to chlorine in tap water. Appl Environ Microbiol 46, 1134–1139 (1983).
7. RAFIEE, M. et al. The Efficacy of Residual Chlorine Content on the Control of Legionella Spp. In Hospital Water Systems. Iran J Public Health 43, 637–644 (2014).
8. Besic, A., Obradović, Z., Dautbegovic, A. & Obradovic, A. The effect of temperature and chlorine residual on the presence of Legionella spp. in water systems of public and tourist facilities. Journal of Health Sciences 7, (2017).