Listeria and Pseudomonas: a risk to your product

The presence of Listeria or Pseudomonas in water and process installations is a risk that every QA manager wants to prevent. It can indicate insufficient hygienic control and biofilm formation in pipes and systems within the food industry. As a result, not only is your process at risk, but potentially your end product as well. Proper disinfection can prevent your product from becoming contaminated with Listeria or Pseudomonas.

What are Listeria and Pseudomonas?

Listeria is a bacterium that can survive well in moist industrial environments (1) and is resistant to low temperatures. (2) Within production and water installations, Listeria can establish itself in biofilms on surfaces such as pipes, drains, machinery, and even in (frozen) raw materials. (4, 5) Contaminated water can also be a source of Listeria. (6)

Pseudomonas is a waterborne bacterium known for its strong ability to form biofilms. (3) This bacterium is common in piping systems, wet zones, and process water, and is highly resistant to disinfection when it is part of a biofilm. Pseudomonas is often associated with recontamination and persistent microbiological problems in industrial installations.

Both Listeria and Pseudomonas share one important characteristic: their ability to protect themselves within a biofilm. This makes them particularly persistent in industrial environments, even after cleaning or disinfection. To understand why these bacteria are so difficult to combat, it is essential to know exactly how biofilm develops.

Listeria and Pseudomonas are bacteria that easily attach to wet surfaces and can survive in water systems. Once this biofilm has formed, it is difficult to remove and becomes a constant source of contamination.

The risk: contamination of your end product

When Listeria and Pseudomonas remain present in water or process systems, there is a direct risk of contaminating the final product. This can lead to a loss of quality and a shortened shelf life as microorganisms spread throughout the process. Furthermore, microbiological deviations increase food safety risks and can lead to product recalls. During audits, elevated germ counts or indicator organisms can result in rejections or non-compliances within HACCP, BRC, IFS, and GMP systems.

The consequences extend beyond product quality alone; contamination can also lead to production downtime and significant financial losses.

It is therefore crucial that a system is properly disinfected: Watter can help with this by continuously introducing disinfectant into the system, thereby preventing the formation of biofilm.

Proven effectiveness of Watter

The effectiveness of Watter is supported by EN testing, including EN 1276. This test demonstrates the disinfectant's efficacy against bacteria such as Listeria and Pseudomonas. Additionally, our system produces the disinfectant in-situ (on-site), allowing for a constant and controlled dosage within water and process systems.

Through this continuous disinfection, microbiological growth is actively inhibited, and biofilm is not only combated but structurally removed. Watter has a proven track record in the removal and control of biofilm, even at low concentrations, making it suitable for long-term application in industrial installations.

Because of this in-situ production, the storage or transport of chemicals is no longer necessary. This increases safety, reduces operational risks, and ensures the constant availability of disinfection within the process.

Sources:

1. Ferreira, V., Wiedmann, M., Teixeira, P., & Stasiewicz, M. J. (2014). Listeria monocytogenes persistence in food-associated environments. Journal of Food Protection, 77(1), 150–170. https://doi.org/10.4315/0362-028X.JFP-13-150
2. Carpentier, B., & Cerf, O. (2011). Review — Persistence of Listeria monocytogenes in food industry equipment and premises. International Journal Of Food Microbiology, 145(1), 1–8. https://doi.org/10.1016/j.ijfoodmicro.2011.01.005
3. Briega, I., Garde, S., Sánchez, C., Rodríguez-Mínguez, E., Picon, A., & Ávila, M. (2025). Evaluation of Biofilm Production and Antibiotic Resistance/Susceptibility Profiles of Pseudomonas spp. Isolated from Milk and Dairy Products. Foods, 14(7), 1105. https://doi.org/10.3390/foods14071105
4. Colagiorgi, A. (2017). Listeria monocytogenes biofilms in the food industry. Pathogens, 6(3), Article 41. https://doi.org/10.3390/pathogens6030041
5. Althaus, D., Zweifel, C., & Stephan, R. (2022). Occurrence of Listeria monocytogenes in raw vegetables and salads from retail and catering businesses in Switzerland. Food Control, 139, 109069. https://doi.org/10.1016/j.foodcont.2022.109069
6. Wartha, S., Huber, S., Kraemer, I., Alter, T., & Messelhäußer, U. (2023). Presence of Listeria at primary production and processing of food of non‑animal origin (FNAO) in Bavaria, Germany. Journal of Food Protection, 86(1), 100015. https://doi.org/10.1016/j.jfp.2022.11.007