Ensure Effective Legionella Analysis and Sampling with These Recommended Tips

October 27, 2020

By: LISA NGUYEN

As we move towards reopening from this pandemic, Legionella testing has been ramping up to ensure the safety of our front-line defenders battling COVID-19, educators, and future generations from the stagnant water left within buildings during the shelter-in-place. Here are some tips we’ve gathered for you that can help you save valuable time and mitigate potential business risks before you begin your sampling.

Equip with These 5 Tips for Your Next Drip 

1. Use appropriate containers and preservatives for water samples.
Samples should be collected in either 250mL or 1L sterile plastic bottles with sodium thiosulfate (chlorine neutralizing agent) and placed in an insulated cooler or bag with sufficient cooling media (ice or icepacks secured in bags to prevent leakage) to last during transit. The acceptable sample temperature is less than 10°C, but not frozen, if samples arrive to the laboratory after the day of collection. The cooling process controls the growth or decaying of legionella bacteria.

*Deliver your samples to your lab immediately if possible.

2. Ensure you have the right volume required for various sources of water samples.
The volume of sample required to be collected is dependent on expected bacterium concentration, which can be determined by the water source. Potable water is expected to have lower density of bacteria and would require larger volume in order to be concentrated prior to analysis. Non-potable water is expected to have higher density of bacteria and can forego the concentration step; thus, smaller volume is required.

*Examples of potable water sources are drinking fountains, showers, sink faucets, etc.
*Examples of non-potable water sources are cooling towers, decorative fountains, whirlpool spas, etc.

3. Watch out for common sample collection issues.
A common issue in sampling collection is that the containers are overfilled to the neck of the container. Samples should be collected only to the fill-line (or about 1 inch of space from the top). The space allows for homogenization of the sample through inversion of the container and reduces the possibility of lab contamination when transferring the samples during the analysis. In contrast, if the container is filled below the fill-line then analysis cannot be performed due to insufficient volume. Thus, samples may get rejected by the laboratory if improper volume is collected, requiring clients to resample.Another common issue is in the removal of aerator in faucets prior to potable water sampling. This leads to potential cross contamination of other bacteria that are present in the aerator that may cause interference in analyzing your sample (i.e. legionella morphology mimicking has been observed when there’s heavy growth of heterotrophic bacteria).

* Do NOT fill the container to the neck of the bottle.
* Remember to remove any aerator before sampling sinks or showerheads.

4. Reduce potential sampling cross contamination.
Remove any stubs from the broken sterility label where the thread of the container meets the cap. This will ensure that any remnant will not get caught between the thread and potentially contaminating your sample. Take extra precaution to ensure that the opening of the bottle and the lid does not come into contact with anything else besides the water.

*To reduce cross-contamination, secure each sample in individual zip-lock bags.

5. Determine your legionella testing requirements and contact your laboratory
By determining your testing requirements, you’ll be able to narrow your search for a laboratory that can accommodate your testing needs and assist with providing you sampling containers. Testing requirements would include but not limited to: the methods, result parameters, sample source, and number of samples to be collected.

*Contact your lab to request containers and plan for your next Legionella Testing.

Tip, Tip, Hooray!
Hopefully, this quick reference guide brings you a step closer towards serving your purpose in protecting the health and safety of the community, in which you operate in, by preparing you for your next Legionella sampling.

For More Information
For more information about industry best practices for companies to consider post COVID-19 re-openings, click here.
For a detailed outline of the CDC Legionella culture-based method, click here.
For the CDC Legionella sampling procedure, click here.

We Can Help
Have questions about legionella? Our experts can help. Click here to start a conversation.

Lisa Nguyen
Project Manager
Lisa brings over 3 years of experience to the Enthalpy team in her current role as Project Manager. Lisa has a B.S. in Environmental Science with a concentration in chemistry.

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