Legionella Analysis Services

cdcelite Legionella is a bacterium that is the agent of Legionnaire’s disease and Pontiac fever. It is primarily caused by Legionella pneumophila and is one of the most challenging building acquired diseases in the industrial hygiene community. According to CDC, over a year 8000 – 18,000 cases are estimated to be caused by Legionella. Currently there are fifty species of Legionella with more than 70 serogroups that make up this genus. Approximately twenty of the species are implicated in human infection. L. pneumophia causing 90% of infection. Legionella occurs naturally in freshwater environments, including lakes, mud and streams. In building systems, is colonizes cooling towers, evaporative condensers, showers, recreational waters (spas) and fountains.

Aerobiology uses the CDC method for recovering Legionella from environmental samples. We are CDC Elite certified.

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AIR, Legionella Culture 10 days Click Here Click Here
WIPE, Legionella Culture 10 days Click Here Click Here
BULK, Legionella Culture 10 days Click Here


Legionnaire’s disease caused Legionella pneumophila is one of the most challenging building acquired diseases in the industrial hygiene community. According to CDC, over a year 8000 – 18,000 cases are estimated to be caused by Legionella. Most of the cases reported are sporadic and nosocomial infections.

The Organism

Legionella are gram-negative rods and require selective media to grow. These are mesophilic bacteria (35- 37°C). To date, there is 50 known species of Legionella and about 70 serogroups have been recognized to cause diseases in humans. The most common species of legionella that causes legionnaire’s disease is Legionella pneumophila serogroup 1.


The natural habitats of Legionella are environmental waters like lakes, streams and rivers. They thrive in warm waters. Natural rubber, plastics and wood influence the growth of Legionella while copper inhibits the growth. Legionella sp. may be isolated from:

  • Surface water, mud and from thermally polluted lakes and stream.
  • Hot water tanks, cooling towers, evaporative condensers, humidifiers, and holding tanks.
  • Decorative fountains, ultrasonic mist machines, whirlpool bath.
  • Spas, respiratory therapy equipment, showers, water faucets, technical-medical equipment.
  • Fire sprinkler systems, safety showers, and industrial process equipment.
  • Damp potting soil.

Infection and Transmission

Legionella causes the disease Legionellosis. The most common clinical types are the Legionnaire’s disease and the Pontiac fever.
Disease transmission occurs mainly by inhalation of the infectious aerosols from workplace, hospitals or industrial settings.
Not spread by person to person


Use of control measures like:

  • Industrial hygiene practices and maintenance procedures.
  • Routine environmental monitoring.
  • Effective disinfecting methods that include chlorination, ozonation, use of ultraviolet, heat-flush (heat shock) method and copper-silver ion systems.

Sampling Procedure

Water Samples

Water samples are the practical way to sample for Legionella. Legionella counts will be more accurate in water than air and testing will indicate the potential risk of exposure. When sampling for Legionella always use a sterile container containing sodium thiosulfate. Samples should be kept cool and overnighted to the lab for analyses. Samples should be received at the laboratory no later than 72 hours from sampling.

Non-Potable Systems – Cooling Towers and Evaporative Condensers

Samples can be collected in a sterile 250 mL bottle containing sodium thiosulfate. When collecting from the reservoir the bottle should be inverted under the water and moved in a single direction. Try not to collect excess sediment in the water samples.

Decorative Fountains, Hot Tubs, Fire Sprinkler Systems, Cisterns, and Humidifiers

Samples should be collected in a 250 mL bottle containing sodium thiosulfate. Include water from the bottom and near the sides of the reservoir.

Potable Water Systems

Hot Water Systems

Two samples should be taken when sampling a hot water system. A preflush sample and a post-flush sample. When collecting the pre-flush sample, turn the hot water tap on immediately collect the first 250 mL of water containing sodium thiosulfate. Sinks, showerheads, hoses, or bottom of hot water tank are all places samples can be taken. When collecting the post flush sample, allow the water to run for 1 full minute or until water sample is hot then collect the sample in a 250 mL bottle containing sodium thiosulfate. By pulling two samples you can determine if the contamination is at the fixture or from the supplied water in the plumbing lines.

Cold Water Systems

Cold water systems can be analyzed by collecting the first draw sample. Drinking fountains, faucets, and showerheads are the appropriate outlets to sample. Collect 250 mL of water in a sterile container containing sodium thiosulfate.

For testing Legionella in domestic waters such as drinking water, water coolers, chillers, eye washers, etc., samples may be collected in sterile 1000 ml or 250 ml bottles with sodium thiosulfate. The 1000ml bottles are available from the lab upon request.

Swab, Air, and Bulk

Swab sampling is a method recommended done alongside water samples. Results from surface samples protocol are recommended, consisting of Buffered Charcoal Yeast Extract Agar (BCYE), BCYE with antibiotics and Blood Agar.

Bulk Samples

Bulk samples can be tested for Legionella. Often samples are sludge from the bottom of a condensate pan scraped off a cooling coil. Samples should be collected in a sterile container, kept cool and transported to the laboratory within 24 hours of collection.


Legionella cfu/ml Cooling Towers & Evaporative Condensers Potable Water Non-potable Water
Detectable but <1 1 2 3
1-9 2 3 4
10-99 3 4 5
100-999 4 5 5
1000+ 5 5 5
1 = Low level of concern and recommend assessment of routine maintenance program.
2 = Little concern and recommend resampling in a few weeks to determine Legionella amplification.
3 = Increased level of concern and disinfection should be considered based on review of the site.
4 = Disinfection is indicated, uncommonly high levels of Legionella. Elevated levels may cause outbreaks.
5 = Disinfection should be preformed immediately. Very high levels indicate outbreak potential. Post treatment analysis should be preformed to ensure complete disinfection.
To learn more about Legionella testing and our related services please request information using the form here or call us at (877) 648-9150. Thank you!