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Environmental Swabbing

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 The Top 5 Mistakes You Could Be Making


We all know just how important environmental monitoring is to a safe food manufacturing plant. Environmental monitoring programs (EMPs) aim to screen for pathogens and/or indicator microbes that could be growing in the production facility and the surrounding areas, alerting you to problems before potential contamination of product occurs. The success of such programs hinges not only on consistent implementation and testing, but also on the effective swabbing of your plant. Below are the top 5 mistakes our experts see plants make when sampling and submitting swabs and sponges for testing.


1. Wrong Swabbing Implement - Before sampling even begins, it is crucial that an appropriate sponge or swab is selected.

Not all buffer solutions are created equal; know what kind of sanitizers are used in the space and plan accordingly. You’ll want to choose a sponge that deactivates these appropriately without interfering with the detection platform used to run the micro analysis.


2. Location, Location, Location - Not just important for real estate! When it comes to environmental monitoring, where you swab matters.

  • Do some detective work—find those places that are difficult to clean: in the nooks and crannies of machinery, around drains, or ledges that might trap product. This is where you are more likely to find bacteria growing, as opposed to the more easily cleaned flat stainless steel surfaces.
  • Use a “zone cleaning” approach to ensure a selection of locations both in the plant floor, and outside locations (like your employee break room, rest room, etc.). Bacterial growth anywhere in the plant has the potential to be tracked into your production areas.
  • Know what pathogens pose the greatest risk in the area you’re testing. Listeria prefers a moist, cold environment, while Salmonella can grow in moist or dry places.


3. Improper Use of Sponge - Handling your sponge incorrectly can lead to inaccurate results, and/or undetected plant contamination.

  • Let sanitizers dry before collecting a sample. If you attempt to swab on a surface still wet with sanitizer, this can reduce the sensitivity of testing and/or cause interference that could affect your final micro results.
  • Sponges are meant to scrub the surface they are sampling, not be delicately swiped. Use both sides and sample vigorously. This will help break up any biofilms that could be trapping pathogens.
  • Handles on “spongesicles” and like products must be broken off prior to fully inserting the sponge into a sterile bag. If they are left attached, other microbes from your hand, the environment, etc. can be transferred, compromising the sample.


4. Sponges Arrive Too Hot or Too Cold – No matter the season, always keep your samples protected from the elements.

To prevent loss in viability of organisms, sponges and swabs should be received between 0 and 8°C. Too cold, and they may die off, too hot and you could experience an overgrowth of bacteria that will out compete the pathogens of interest.

To this end, keep swabs refrigerated until the time of shipping. We advise sending them out for testing in a foam cooler with ice packs. The foam helps insulate from external temperature changes, while the ice packs keep the internal temp consistent and low.


5. One Sponge, Multiple Pathogens - If you will be submitting for multiple pathogens from one site, be sure that each organism is assigned its own sponge.

While plated tests (like Aerobic Plate Count, E coli/Coliform, Yeast/Mold) can all be run from the same sample, to enrich for multiple pathogens (like Listeria and Salmonella) the lab must aseptically split sponges, which decreases test sensitivity and can increase chances of cross contamination. To mitigate risk, swab each dual pathogen testing area with multiple sponges, or purchase a specialty sponge with two heads that can be easily separated and enriched.


Environmental monitoring can seem like a daunting, and at times confusing, task. By looking out for the pitfalls noted above, however, you’re on your way to ensuring an effective program. If you’re not already set up with such a program and looking for more information, consider browsing the full-length EMP whitepaper available here. Your decisions impact the quality of your products: be informed, and establish good practice now. That proactivity could end up saving you and your business money (and headaches) down the road.



Laura EvenstarThe Author:

Laura Evenstar - Client Service Representative

Eurofins Microbiology Laboratories (Mounds View, MN)