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Environmental Pathogen Management | How To Plan Your Hunt

14 Mar 2019

Environmental Pathogen Management | How To Plan Your Hunt

The purpose of an environmental pathogen programme in your factory is to “seek” the target and surveillance pathogens. There is no value in swabbing your factory without a clear rationale or plan. If your programme is not designed to find pathogens, it is not effective, and chances are the results may leave you with a false sense of security (like having a smoke alarm with an empty battery).

To find a pathogen, you need to think like a pathogen!

All micro-organisms (including pathogens) require three essential conditions to grow and thrive in your factory environment: food, moisture and shelter (to provide time to grow). Of course, there are other conditions, like oxygen and temperature, which differ between species, however, by controlling food, moisture and shelter in your factory, pathogens will struggle to get established.

Food is minimised by having a clean plant, moisture is controlled by keeping your factory as dry as possible during production and shelter is eliminated by good design and maintenance of your equipment and buildings.

One way to hunt for pathogens is to walk into your plant and swab the dirtiest spots you can find, targeting the “food – moisture – shelter” areas (I call this: a worst-case random sampling programme). Unfortunately, for routine monitoring, this approach can become a logistical nightmare because a positive result in a fully random programme often doesn’t tell us how long the contamination has been there. If we have a fully random programme targeting the worst-case areas, chances are we may end up chasing our tail.

For example, I once had a client tell me, they kept finding positives in a contaminated area of the plant. They were on continuous traceback (and spending an absolute fortune on testing). Whilst it was wonderful that they were finding pathogens, they could possibly change their tactics and “stop sticking their swab in the bad spot to confirm the pathogens were still there”.

My recommendation was to focus their efforts on isolating the area, fixing the floor (it was badly damaged) and swabbing surrounding areas to monitor if the contamination was spreading.

For a routine programme, we need a structured plant monitoring approach, starting with the premise that the plant is clean (with no food – moisture – shelter), because going pathogen hunting in a dirty plant can be like “shooting fish in a barrel”.

To design the routine programme, we can use risk management principles.

Most International guidelines on Salmonella and Listeria environmental monitoring are based on proximity: the closer you are to the product the higher the risk for product contamination. Most guidelines include four proximity categories: product contact surface, close, further and far. Unfortunately, defining the differences between close, further and far has been difficult and can be ambiguous.

My approach is based on three clearly defined proximity categories: close (the outside of process equipment), far (floors, walls, drains) and moving (stuff that moves between far and close). I consider product contact surface swabbing for pathogens the same as final product testing because a positive result for a product contact surface means our product is contaminated (we have moved from the smoke into the fire).

Something that is not covered in the guidelines is the actual food process itself. Clearly, it is not possible for a generic pathogen guideline to cover all the different food processes, however, I believe it is really important to ask two very relevant process questions for environmental pathogen management.


  1. Does your process have a validated kill step?
  2. Is your product enclosed or exposed to the factory environment following this kill step?

If we have a validated pathogen kill step in our process, we can expect to find pathogens before this kill step. Swabbing extensively in this area would only confirm what we already know.

If our product is exposed following the kill step, the risk of environmental re-contamination is high, and we should focus our pathogen hunt in this high risk “post-kill zone” of our factory.


When it comes to pathogens in our factory environment, the risk to the product increases depending on how close we are to the product and where we are in the process.


Let’s look at a smoked sausage plant. In a well-designed factory, products are prepared in the raw “pre-kill” area (Listeria expected), pushed into a double door cooker (kill step) and pulled out into the clean “post-kill” side to be packed (Listeria not-expected). To me, swabbing packing equipment in the “post-kill” zone, close to the cooked sausages will be more meaningful than swabbing the floors in the raw “pre-kill” zone.

This risk-based approach (using proximity and process) gives us a logical starting point for our environmental pathogen monitoring efforts. We should target the high-risk areas in our factory and design our response plans accordingly (to be discussed in my next article).

Unfortunately, whilst this risk approach will guide us and ensure our programme targets the right areas, it does not tell us, how to pick our sample points. This activity requires an initial plant risk review to identify and map traffic flows, people movement and process access points.

To complete this initial task, I recommend using expert input (independent from your factory), because when it comes to planning a pathogen hunt, nothing beats a fresh pair of knowledgeable eyes.


About The Author

With over 30 years experience in the global food industry, Jack has led the international food safety assurance team at Fonterra and is currently working as an independent consultant. Jack has managed consultancy projects in the USA, Europe and China and led the design of Fonterra’s Environmental Pathogen Monitoring Programme. If you would like to get in contact with Jack, you can do so by emailing him at

Jack van der Sanden

Food Safety Consultant
14 Mar 2019

Contact Jack van der Sanden


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