Legionella Sampling Guide

Legionella
Sampling Guide

Legionellaceae are ubiquitous in surface water, groundwater, estuarine environments. Most outbreaks of disease due to Legionella are due to contaminated mist from cooling towers and potable water distribution systems. Exposure occurs from contaminated, aerosolized water.

We offer four different culture-based methods depending upon the level of information you need. For more information about the different tests please go to www.legionellatesting.com. All culture tests require 10-14 days before completion.

We also offer several different PCR methods depending upon the information you need. More information about these can also be found at www.legionellatesting.com. While the culture method is considered the “Gold Standard”, PCR is useful for ruling out possible Legionella contamination in time-sensitive projects. PCR results can be requested same-day, 24 hrs and 48 hrs depending on your needs.

Where to Look

This is a list of water systems that have been demonstrated to harbor Legionella bacteria and have been associated with outbreaks. Their investigation should be included in any Legionella Risk Assessment program:

Potable water systems
Cooling towers
Aerosol generation during the biological treatment of some industrial process wastewater streams. For example, pulp and paper manufacturing, food and beverage manufacturing and pharmaceutical manufacturing.
Aerosol generation during municipal water and wastewater treatment
Raw, utility or fire water
Ornamental outdoor and indoor water fountains and ponds
Heated swimming pools
CPAP water
Potting soil
Hot tubs
Humidifiers
Metal working fluids
Medical therapy equipment like dialysis units, nasogastric tubes, respiratory equipment and nebulizers, whirlpool baths
Commercial car wash facilities particularly those using recycled water
Supermarket vegetable misters
Ice machines in hotels and hospitals
Outdoor body misters at ballparks and amusement parks*

*Has not been associated with any cases of legionellosis.

Sampling Considerations

Water samples must be collected in sterile vessels (available from EMSL).
A 1 L water sample is recommended for potable waters (containing sodium thiosulfate).
Less than 1 L is acceptable if higher levels of bacteria are suspected.
Chlorinated water must be treated with sodium thiosulfate.
100-250 mL is typically sufficient for non-potable water samples.
In addition to collecting water samples it is useful to collect a swab of the biofilm found in the water supply pipes.
Samples must be transported to the laboratory within 24 hrs in coolers with freezer packs.

Cooling Tower Sampling Locations - Sample Quarterly

Tower Makeup
Tower Sump away from makeup* (water and swab)
Inlet to Heat Exchanger
Outlet from Heat Exchanger
Distribution Pack
Tower Pack* (water and swab)

Potable Water Sampling Locations - Sample Semi-Annually

City Water Main Entry Point
Storage Tanks
Hot Water Heater Drain Point*
Hot Water Return
Last Point on Cold Water/First Point on Hot Water
Last Point on Hot Water*/First Point on Cold Water
10% of Selected Outlets (water and swab)*

*Test routinely

Legionella Routine Sampling Locations

Test all locations to establish a baseline
Test all locations during an outbreak

Sample Collection

Collect water samples from the or from the cooling tower basin water, hot water storage tanks, showers, water taps, etc.
If sampling for PCR analysis, collect 100 mL of water and another 1000 mL if potable water or 250 mL if non-potable water is sampled if culture results are also needed.

Sample Shipping

Label sample number on the bottle and record on the chain of custody.
Use a distinctive number for each sample. Complete all sample information on a sample data sheet for your own record. Send a copy with the samples to the laboratory. You can download a copy of the Chain of Custody form on our website www.emsl.com.
Tightly cap the bottles. Make sure that water does not leak during shipping and transporting. Taping of the bottle around the cap and neck with electric vinyl tape is recommended. Place taped bottles in a clean plastic bag.
Place the samples in insulated boxes or on freezer packs to protect them from extreme temperature fluctuations in the summer months. NEVER USE ICE OR DRY ICE. Stuff the box with foam chips to cushion, and seal the box securely for shipping. Send samples by overnight express carrier. Schedule sampling between Monday and Friday so that samples can be delivered to the laboratory no later than Saturday.