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A Primer On Legionella

A Synopsis on Legionella

Legionella, the bacteria responsible for causing Legionnaire’s disease, is one of the most significant sources of waterborne disease outbreaks in the U.S. Investigations by the CDC have indicated that many cases could have been prevented through better water management. We’ve previously written about Legionnaire’s disease and how ATP testing can be used as a component of a water management plan. In this article, we will discuss how Legionella-specific tests can be used in the monitoring tool kit.

Legionella-specific testing methods

Legionella-specific testing may be performed for different purposes, including routine monitoring to verify the efficacy of the water management program, for identifying high risk or critical control locations in a water system, or as part of an investigation to identify potential sources of an outbreak. Common Legionella-specific test methods include culture tests and quantitative Polymerase Chain Reaction (qPCR) testing.

Legionella culture tests are performed by growing the organisms on selective media. The method is complex and performed by specialized laboratories. One advantage is that the tests are well-established and familiar to many water system owners and operators. Because of this, there are many references available to help establish action levels based on culture results. One downside, however, is that the test requires long incubation times, so results are often not available until 10 to 14 days after samples have been collected. Culture tests may also underestimate true quantities because they will not detect viable cells that are not culturable.

qPCR testing is a rapid DNA based method that is increasing in popularity and acceptance for monitoring Legionella.

The biggest advantages of qPCR testing are:

  • The test is rapid, allowing for results within 2.5 hours of sample collection, and
  • The test is sensitive and can detect viable but non-culturable cells.

The high sensitivity and rapid results allow qPCR to be used as a quick screening tool for both investigative and routine monitoring. Moreover, qPCR field kits ensure that results are representative of field conditions, preventing any potential changes that could occur in the sample while it’s being transported to the lab.

Given their different strengths, these two test methods can complement each other as part of a comprehensive monitoring program.

LuminUltra’s GeneCount® qPCR solutions and services help monitor for Legionella. If you have any questions or would like more information about how you can use LuminUltra’s Legionella species or Legionella pneumophila qPCR assays to help monitor your water management program, contact our Technical Support Team for help.


Brad Mcilwain

Brad McIlwain has over eight years of experience in the water and wastewater industry. Prior to joining LuminUltra, he worked for several years as a consulting engineer, where he helped solve complex water and wastewater treatment process issues. He has a particular interest in water system corrosion. During his Master’s, his research focused on water quality and corrosion in premise plumbing. Brad enjoys being outdoors, spending as many weekends as possible camping, hiking, and cycling.

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