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Legionella Lab Services for Legionella Water Testing in Cooling Towers and Water Systems

Is Legionella Water Testing Important?

Outbreaks of Legionnaires' disease receive significant media attention especially when a large number of people become ill or die. In contrast to highly publicized outbreaks, single infections with Legionella bacteria often go unnoticed. According to the Centers for Disease Control and Prevention (CDC), between 8,000 and 18,000 people are hospitalized with Legionnaires' disease in the United States each year. Legionnaires' disease is a legitimate public health concern as its fatality rate during an outbreak ranges from 5% to 30% in those who contract the disease. The immediate consequences for the building owner or manager faced with liability claims and negative publicity can be devastating and extremely costly. Many experts agree that proactively managing the risk of Legionella bacteria in cooling towers and water systems is more cost effective than responding to an outbreak retroactively.

While a few states and municipalities have instituted guidelines for monitoring Legionella, there are no federal or state regulations that require routine monitoring of buildings with susceptible individuals. We recommend building owners and hospitals establish a Legionella control and management program, including routine monitoring and testing, in areas where the risk of Legionella infection is high. This accomplishes two tasks:

1) It indicates the effectiveness of control measures already in place, and
2) It provides an early warning of potential problems.

Legionella in Cooling Towers and Water Systems

Although some species of Legionella can be found in the soil, most species live in water. The Gram-negative Legionella bacterium thrives in warm, stagnant water but it can survive under a wide range of temperatures (68° to 122°F), pH and dissolved oxygen levels. Legionella pneumophila has been isolated and associated with outbreaks stemming from air-conditioning cooling towers, whirlpool spas and showers. Other water devices can include potable water systems, whirlpool baths, respiratory care equipment, humidifiers and faucets. As water from these sources is aerosolized, individuals inhale the Legionella-containing droplets and the organism is aspirated into the lungs. Smokers and individuals with weakened immune systems have a higher risk of developing Legionellosis (Legionnaires' disease or Pontiac fever).

Lab Services: Legionella Detection Methods

Legionella Culture Method
The culture method remains the "gold standard" for detecting Legionella from environmental sources. This technique, unfortunately, requires up to 10 days to complete, precious time that could be used to pinpoint Legionella sources and prevent additional exposures.

Legionella PCR Method
Another Legionella detection method is polymerase chain reaction (PCR), a molecular technique that offers a very sensitive method and only requires a few hours to complete. The PCR method provides an extremely powerful screening tool for the rapid Legionella detection in environmental samples, although it doesn't distinguish between living and dead cells. But unless the environment has been recently altered, such as with a biocide application, moderate to high populations of Legionella detected by PCR are usually indicative of an existing or potential future problem. Therefore, the PCR method can rapidly identify potential sources, facilitating disinfection processes and help to prevent further exposures. Because this method does not determine viability of the Legionella bacteria, the PCR screen must be considered presumptive and requires confirmation via conventional culture techniques.

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Sampling Methods: Swab and Bottle

Swab Sampling
Collect a surface sample with a sterile swab where there is scale build up or on water outlets. Swabs of faucet aerators and shower heads should be taken before the water sample from these sites with the aerator or shower head removed if possible. Pre-wet the swab with water from the sampling site and submerge swab in 3-5 ml of water taken at the same time to prevent drying during transport. For more information refer to OSHA's Water Sampling Protocol.

Bottle Sampling
Equipment Needed for Legionella Water Sampling

  • Sterile bottle with Sodium Thiosulfate preservative

  • Gloves

  • Respirator (Wear appropriate respiratory protection during the examination of water systems if a significant potential exists for exposure to high concentrations of contaminated aerosols)

  • How To Sample for Legionella in Water
    1. Wear gloves and, if necessary, respiratory protection.
    2. Use sample bottles provided by the analytical laboratory that contain a sufficient type and amount of neutralizer for any disinfectant agent in the water system.
    3. Collect a "pre-flush" sample of the first water drawn from bottom drains and outlet valves of storage tanks, sumps, and water heaters as well as faucets and showerheads.
    4. Allow the water to run until the temperature stabilizes and collect a second "post-flush" sample when the water temperature is constant.
    5. Do not overfill sampling bottle because it will rinse out neutralizer.
    6. Replace cap.
    7. Label sample container appropriately.
    8. Ship samples on ice to the Legionella testing laboratory.
    Note: Refer to OSHA's Water Sampling Protocol for detailed instructions.

    Quality Control for Legionella Water Testing

    The number and types of sites that should be tested must be determined on a case-by-case basis. Due to the diversity of plumbing and mechanical systems in buildings, you may need more than one sample from the suspect source. Generally, any water source that may be aerosolized should be considered a potential means for the transmission of the Legionella bacteria.

    Trusted Lab Analysis for Your Legionella Testing

    Are you involved with Legionella monitoring programs or Legionella outbreak control?

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    Legionella sp. Colonies on Agar Cultured Plate, Illuminated with UV Light
    Legionella sp. colonies cultivated on an agar cultured plate and illuminated using ultraviolet light.
    Copyright © Centers for Disease Control

    Gram-stained Micrograph of Legionella pneumophila Bacteria
    Gram-stained micrograph of Legionella pneumophila bacteria from a victim of the 1976 Legionnaires' disease outbreak in Philadelphia.
    Copyright © Centers for Disease Control

    Transmission Electron Micrograph of Legionella pneumophila
    Transmission electron micrograph of Legionella pneumophila.
    Copyright © Centers for Disease Control

    Legionella on BCYE Agar Plate
    Legionella on BCYE agar plate.
    Copyright © EMLab P&K