CDC photo

Maine Environmental Laboratory is nationally accredited to test both potable and non-potable water for Legionella pneumophila. We are the only lab in New England accredited to do so.

Legionella pneumophila is the bacteria responsible for Legionnaires’ Disease, a pneumonia that can infect humans through the inhalation of bacteria-laden water vapor.  It has a 9% fatality rate.  While Legionella exists naturally in the environment where it poses little risk, in built environments, its population can thrive and get amplified in warm and stagnant conditions, and in some situations, get airborne as a mist from water coolers, showers, spas, fountains, humidifiers, etc.  Maine Environmental Laboratory tests for Legionella bacteria for clients such as hospitals, nursing homes, HVAC engineers, cruise ships and gyms.

LD Pneumonia

From the U.S. Centers for Medicare and Medicaid Services (CMS):

The bacterium Legionella can cause a serious type of pneumonia called LD in persons at risk. Those at risk include persons who are at least 50 years old, smokers, or those with underlying medical conditions such as chronic lung disease or immunosuppression. Outbreaks have been linked to poorly maintained water systems in buildings with large or complex water systems including hospitals and long-term care facilities. Transmission can occur via aerosols from devices such as shower heads, cooling towers, hot tubs, and decorative fountains.

Examples of these system components and devices include:

Potable Water Non-Potable Water
Aerators Air conditioners
Bath taps Car washes
Bathroom faucets/sinks Centrally-installed misters, atomizers, air washers, and humidifier
Drinking fountains Chilled-water return tanks
Drinking water Cooling towers
Electronic and manual faucets Decorative fountains
Eyewash stations Evaporative Condensers
Faucet flow restrictors Header Tanks
Hot and cold water storage tanks Hot tubs/saunas
Ice machines Machine/utility waters
Kitchen faucets/sinks Medical devices (such as CPAP machines, hydrotherapy equipment, bronchoscopes, heater-cooler units)
Showerheads and hoses Non-steam aerosol-generating humidifiers
Showers Pipes, valves, and fittings
Water filters Pools
Water heaters Rainwater storage tanks
Water-hammer arrestors

Legionella Testing Regulation

In June, 2017, the Centers for Medicare and Medicaid Services published a memorandum titled "Requirement to Reduce Legionella Risk in Healthcare Facility Water Systems to Prevent Cases and Outbreaks of Legionnaires’ Disease.” Healthcare facilities must now develop a water management program to identify areas where Legionella could grow and spread. A critical part of the program is monitoring the effectiveness of the plan. An easy way to monitor the effectiveness of the plan is to collect samples at pre-determined sampling points, and test for Legionella pneumophila.  If the results are negative, the plan is working.

The CMS policy memorandum applies to hospitals, critical access hospitals and long-term care facilities. However, it is also intended to provide general awareness for all healthcare organizations, as well as the maintenance staff of any large building.

Legionella Testing at MEL

Maine Environmental Laboratory uses a reliable test method (IDEXX Legiolert) that is comparable to the traditional culture methods, but takes half the time.  Confirmed results are available after only 7 days.

Sampling is simple, requiring only certified sterile bottles provided by MEL.  Samples do not need to be chilled on their way to the lab, eliminating the need for shipping coolers packed with ice.  The hold time is 48 hours.

How it Works

IDEXX photo.

The method is based on bacterial enzyme activity.  An IDEXX-patented reagent powder is added to the water sample, mixed thoroughly, and poured into a special 96-well counting tray.  The tray is incubated for seven days at 102º F.  If Legionella pneumophila bacteria is present in the sample, it's enzymatic reaction with the reagent powder will turn the water brown or cloudy.

When using the 10 mL protocol for potable water, the Legiolert test detects Legionella pneumophila at ≥10 organisms/100mL. When using the 0.1 mL protocol for nonpotable water, the Legiolert test detects Legionella pneumophila at ≥10 organisms/mL (≥1000 organism/100 mL).


Maine Division of Infectious Disease, "Airborne and Direct Contact Diseases - Legionellosis"

US CDC's "Legionella (Legionnaires' Disease and Pontiac Fever)" (website)

US CDC "Toolkit: Developing a Water Management Program to Reduce Legionella Growth and Spread in Buildings" (website)

US CDC "Sampling Procedure and Potential Sampling Sites" (6 pg pdf.)

US CDC "Developing a Water Management Program to Reduce Legionella Growth and Spread in Buildings" (36 pg. pdf)

MEL Test Method for Legionella pneumophila:

IDEXX Legiolert

Sample Requirements

Container: sterile plastic or glass with sodium thiosulfate
Volume: 110 mL minimum
Hold Time: 48 hours.
Preservation: Transport at ambient temperature in insulated cooler to protect against extreme heat or cold.  Refrigerate if samples will not be analyzed within 24-48 hours of sampling.


Your local solution for Legionella testing! Lab director Jackie Villinski at the Maine Health Care Association Fall Conference, 2018.