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This is the final video in a series addressing environmental aspects of legionellosis outbreak investigations.
It will demonstrate the correct procedure for collecting water samples from spas and fountains for Legionella
culture during a cluster or outbreak investigation, or when cases of disease may be associated with a facility.
Conduct an Environmental Assessment and make a Sampling Plan before collecting samples.
This video should be used in conjunction with the written document, "CDC Sampling Procedure and Potential Sampling Sites."
Call ahead and instruct the facility to turn off but DO NOT DRAIN the spa. This will stop transmission in case this is the source,
but allow samples to be collected later. In situations where indoor, aerosol-generating devices in enclosed
spaces cannot be shut down, wearing a half-face air-purifying respirator equipped with an N95 filter may be appropriate.
Respirators must be used in accordance with a comprehensive respiratory protection program, which
includes fit testing, training, and medical clearance ahead of their use.
Facilities maintenance personnel should always provide access to maintenance areas like the
spa equipment room and they should open filters.
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You should be prepared to collect several swabs from the jets and water line of the spa in addition to a bulk water sample.
Run the tip of the swab firmly against the surface at the water line and inside the jets.
Collect 3 to 5 mL of water from the spa into a 15 mL sterile plastic tube. Place one swab per tube into
enough water to keep the swab tip moist during transport.
Snap the stem about 1 inch from the top of the tube.
Add a drop of 0.1N sodium thiosulfate solution to neutralize residual disinfectants. Tighten the top to prevent leakage.
Then, label each tube with a unique identifier. Record the type and location of the sample on a
Sample Data Sheet, and place the tube into a cooler.
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If the spa is not drained, collect a 1L bulk water sample in a sterile 1L bottle. If the spa is partially drained, a swab tube
may be used to collect the remaining water. If the spa has been completely drained, ask facility maintenance personnel
for access to the compensation tank (for collection of overflow water) and take a bulk water sample from there.
Add 0.5 mL of a 0.1N sodium thiosulfate solution to neutralize residual disinfectants. Tighten the top to prevent leakage.
Label the bottle with a unique identifier. Record the type and location of the sample on the
Sample Data Sheet, and place it into the cooler.
You also need to measure the water parameters. Remember, it is possible for a spa
to pass routine environmental health inspection and still harbor Legionella.
Collect some water in a separate plastic bottle.
Measure the spa water temperature. Make sure there is enough time for the thermometer to stabilize.
Measure pH by placing the paper strip inside the bottle. Compare the colors on the paper strip
with the legend on the box. You may also use a digital pH meter.
It is best to use a pool test kit or digital colorimeter to measure residual disinfectant in spas. Spas may use other halogenic
disinfectants such as bromine. Follow the test kit instructions for conversion. If the residual disinfectant levels
exceed the maximum limit of the test kit, perform serial dilutions to bring the sample within the test kit's range.
If there is a very small amount of disinfectant in the spa, use your potable water test kit.
Record all data on the Sample Data Sheet.
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It is very important to collect a filter sample from spas. The filter is usually located in a separate maintenance room.
Gloves should be worn due to heavy organic loads typically found in filters and the abrasive or caustic nature of some filter filling material.
There are 3 types of filters:
sand, cartridge, and diatomaceous earth.
The method for sample collection depends on the filter type.
When sampling sand filters, collect some sand in a 1L bottle and enough water from the filter chamber to cover the sand.
If the spa has a cartridge filter, cut a portion of the filter to fit inside a 1L bottle and add enough water from the filter chamber to cover it.
If the spa uses a diatomaceous earth filter, collect some water from the filter chamber into a sterile 1L bottle.
Use a sterile swab to scrape diatom powder from the grid. Make sure it is completely covered by at least 1 inch of water.
With each filter sample you take, add 0.5 mL of 0.1N sodium thiosulfate solution to the sample to neutralize residual disinfectants.
Tighten the top to prevent leakage.
Label each bottle with a unique identifier. Record the type and location of each sample on the Sample Data Sheet, and place it into the cooler.
Note that collecting filter samples may disrupt the integrity of the filter, requiring maintenance service or replacement.
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As with spas, call ahead to make sure the fountain is turned off but not drained. Fountains and similar water features require
both biofilm and bulk water sampling, as well as measuring water parameters. The procedure is the same as
sampling spas, with the exception that decorative fountains often do not use filters.
If there is a filter, sample it the same way you would a spa filter.
The number of swabs depends on size and complexity of the feature. Swabs should be taken from
the water line and any surfaces with noticeable biofilm accumulation.
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Using available epidemiologic evidence and your knowledge of the ecology of Legionella, you can determine whether additional samples
are needed from devices like sprinkler systems, eye wash safety stations, humidifiers, and respiratory care equipment.
It is extremely important to make sure you collect, label, record, and transport your samples accurately and carefully.
For more information, please reference the written document "CDC Sampling Procedure and Potential Sampling Sites".
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