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Legionella – Testing

Legionella Testing for Defensible Water Management Plans

Property owners and facility managers protect patients and clients against Legionella and other waterborne illnesses as well as legal and non-legal risks and expenses by implementing Defensible Water Management Plans. These plans including testing and response to test results to demonstrate exercised standards of care in preventing disease such as Legionnaires Disease, which is associated with water systems. Water Management Plans, including practices and procedures in a testing section, need to be reviewed on a regular basis to identify the areas for improvement and adjustments should be made as needed.

Why Legionella Testing?

Why Legionella Testing?

Water Management Programs should include effective strategies to identify and minimize potential risks that could make a facility vulnerable to loss and endanger public safety. Complete and proper management techniques to make facilities less vulnerable include testing for pathogens (harmful bacteria) including Legionella bacteria.

Opportunity exists for Legionella bacteria to form and grow in any stagnant water, 68-120 degrees Fahrenheit. In large facilities, water softeners, filters, cooling towers, hot and cold water storage tanks, evaporative condensers, hot tubs, showers, drinking fountains and fluid containers are areas that harbor stagnant water and have been identified as the main sources for the growth and transmission of Legionella bacteria. The possible contributing factors to the growth of Legionella bacteria in these water system areas include excessive water age, biofilm, lukewarm water temperature, dead legs, insufficient disinfectant, inadequate corrosion and scaling control and cross-connections between non-potable and potable water.

What is Legionella Testing?

What is Legionella Testing?

Testing for the presence of Legionella bacteria is reliably accomplished by culture in an accredited microbiology laboratory using well-characterized and validated methods.

Types of Legionella Tests

Types of Legionella Tests

There are three main methods of Legionella testing:

  • Culture Method – This can take 10 days to complete, so a loss of valuable time needed to identify the source of contamination and the prevention of exposure or spread exists.
  • PCR Method (Polymerase Chain Reaction) – This method takes a few hours to complete and can be a useful method to screen drinking water samples.
  • DFA Method (Direct Fluorescent Antibody) – This method is the original “gold standard” developed by the Center for Disease Control (CDC) in 1978. More specific and sensitive, DFA uses monoclanal fluorescent antibody specific for several serogroups of L. pneumonia and other Legionella species that cause Legionnaires Disease. This method requires specific expertise.

As far as sample collection, there are two main methods: Swab and Bottle.

Swab Collection – Collection of a surface sample with a sterile swab

Bottle Collection – Collection of a bulk water sample

Bottle Collection is the most common method and may include collecting water samples from potable water fixtures or warm-water-containing mechanical equipment. This sampling collection method permits quantitation of the number of Legionella per specific volume of water.

Why Independent Testing?

Why Independent Testing?

It is important to utilize an independent organization for testing. An independent organization reviews the samples and determines the existence or non-existence of pathogens with no bias or discrimination regarding the facility being tested, the water management team, or the type of water systems involved. This practice reduces and protects the underlying liability of the facility being tested as well as the facility water management team.

Where Should I Test?

Where Should I Test?

Intrusion Growth Transmission

Parts of a water system with Insufficient circulation or lukewarm temperature provide the ideal environment for Legionella bacteria intrusion. Once Legionella bacteria forms and begins to grow, it then needs to spread. Any source that generates aerosol or a fine mist of water has the potential to spread Legionella bacteria via transmission.

Sampling locations should be decided by the facility management team. Facilities including hospital, retirement communities, large hotels or apartment buildings and cruise ships are most often associated with outbreaks. Some areas for testing include incoming water, after softeners and or filtration equipment, several spots in the hot water loop, showers, misters, ice machines, faucets, cooling towers and decorative water features. Post-flush samples from plumbing fixtures may also be a testing area.

When Should I Test?

When Should I Test?

An internal environmental risk assessment portion of a Water Management Program should be a living document and regularly reviewed to ensure it remains updated. This is especially important for healthcare facilities and nursing homes as patients are immunocompromised. And in facilities such as hotels and apartment buildings, managers and landlords have a legal duty to assess and control the risk of exposure to Legionella bacteria.

The Center for Disease Control (CDC) advises that the facility water management team should regularly monitor water quality parameters, such as disinfectant levels, temperature levels and age of water. This ensures that building water systems are operating in a way to minimize hazardous conditions that could encourage Legionella and other waterborne pathogens to grow.

Routine environmental sampling for Legionella (sampling that is performed proactively as part of an effort to reduce Legionella growth and transmissions in building water systems, not in the context of an outbreak investigation) is one way to validate the water management system is working as intended.

What If Testing Is Positive?

What If Testing Is Positive?

Active response upon positive testing results should be pre-determined in the Water Management Program documentation as contingency response. Contingency response should include a review of data followed by activities such as flushing or hyper chlorinating the water system. Testing should then take place, again, after disinfection.

The use of internal controls for quality and assurance and quality control should also be outlined in the Water Management Program. Quality Assurance provides confidence that requirements will be satisfied. Quality Control ensures that practices and procedures are in place and followed. The Quality Assurance and Quality Control functions for a facilities water system are generally covered by internal audit processes.

CDC Guidelines for Laboratory Selection

CDC Guidelines for Laboratory Selection

There are five considerations for laboratory expertise:

  • Elite Accreditation
  • Culture Method
  • Level of Identification
  • Willingness to Save Samples
  • Experience with Environmental Risk Assessment and Sampling
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