An essential part of building ownership is ensuring your drinking water is safe. This includes having an active water management program and conducting regular testing for Legionella bacteria.
What is Legionella?
Legionella is a type of bacteria that can grow in your building’s water system. Legionella is pathogenic, meaning that exposure to it can cause disease. It is especially harmful to seniors and immunocompromised individuals, causing a severe type of pneumonia called Legionnaires’ disease.
Why is regular Legionella testing important?
You should regularly conduct water quality tests if you own a multi-story building that could expose people to Legionella. Timely identification of Legionella in your building water system allows you to begin remediation efforts quickly, potentially stopping an outbreak of Legionnaire’s disease before it occurs.
While Legionella poses a threat wherever it may grow, certain types of facilities may benefit more from routine testing, including:
- Facilities that house or treat individuals at increased risk for Legionnaires’ disease.
- Facilities that consistently test positive for Legionella.
- Facilities with a history of Legionnaires’ disease outbreaks.
In addition, some facilities are required to conduct routine Legionella testing by their state or local government or other regulatory agencies.
Types of Legionella water tests
Several types of water tests can identify Legionella. Some test methods may be performed onsite by facility staff, while others may require working with a certified laboratory. Regardless of the test method, it’s important to understand the process and limitations of each.
Standard lab culture
- Water sample collected by facility staff and shipped to a lab where it is grown on a Petri dish.
- Takes 7-14 days to receive test results.
- Detects live (pathogenic), not dead (non-pathogenic) Legionella bacteria.
- Detects all Legionella species and serogroups.
- Yields isolate for additional characterization, such as re-culturing or identifying an outbreak’s origin.
- Results reported in colony forming units (CFU) per volume.
- Most expensive method.
- Accuracy of results is subject to skill, experience, and procedural rigor of the laboratory.
Lab qPCR
- Water sample collected by facility staff, then shipped to the lab where qPCR measures Legionella-specific DNA or RNA.
- Takes 2-4 days to receive test results.
- Results reported in genomic units (GU) which do not correlate to colony forming units (CFU).
- Cannot distinguish between live (pathogenic) and dead (non-pathogenic) Legionella bacteria. The results will show both live and dead.
- Only identifies Legionella pnuemophila and Legionella pnuemophila serogroup 1.
- Does not yield isolate for additional characterization, such as re-culturing or identifying an outbreak’s origin.
- Can be useful for negative screening, but positive results yield limited information.
Alternative methods (e.g., on-site rapid tests)
- Results reported within hours.
- May not detect all Legionella species.
- May not distinguish between live (pathogenic) and dead (non-pathogenic) Legionella.
- Results can be reported genomic units (GU) or colony forming units (CFU), depending on the type of test.
- May be useful for repeated measurements when quick turnaround time is preferred.
- Should not be used as a replacement for lab tests.
For facilities that serve people who are immunocompromised or over 55, like senior communities, nursing homes, and hospitals, regular Legionella testing is a critical piece of your overall water management program and crucial to your facility’s ability to provide a safe and healthy environment for occupants.
