NORWAY – A recent study conducted by researchers from the Norwegian University of Science and Technology has revealed the potential threat posed by Pseudomonas biofilms in food processing environments.
While typically associated with food spoilage rather than foodborne illnesses, these biofilms have been found to aid the survival of Listeria monocytogenes cells even after disinfection.
This discovery highlights the need to recognize Pseudomonas as a direct food safety hazard, as they can protect and shelter pathogens like L. monocytogenes.
Pseudomonas bacteria are commonly found in food processing environments due to their ability to grow rapidly at low temperatures, withstand antimicrobial agents, and form biofilms.
These characteristics make them particularly resilient colonizers in food processing environments, where they can act as food spoilage organisms and protectors of foodborne pathogens.
Link between biofilms and pathogen survival
Previous research has demonstrated that bacteria exposed to sub-lethal concentrations of disinfectants can develop both disinfectant- and antibiotic-resistant properties.
Additionally, biofilms’ interspecies interactions have been found to accelerate horizontal gene transfer, facilitate adaptation to environmental conditions, and reduce susceptibility to antimicrobials.
In this context, multi-species biofilms dominated by Pseudomonas could potentially host and shelter pathogens like L. monocytogenes.
Study methodology and findings
In the study, researchers isolated Pseudomonas samples from cleaned and disinfected surfaces in a salmon processing facility.
Out of the 186 isolates screened, a high variation in biofilm formation was observed, with different isolates categorized as strong, medium, weak, or non-biofilm producers.
Testing the isolates in both planktonic and biofilm states, the researchers found that Pseudomonas exhibited higher tolerance to a commonly used peracetic acid (PAA)-based disinfectant and the antibiotic florfenicol compared to other bacteria types.
Most isolates displayed significantly higher tolerance in the biofilm state than in the planktonic state.
When L. monocytogenes was co-cultured with Pseudomonas in a multi-species biofilm, its growth was noticeably reduced compared to L. monocytogenes in monoculture.
However, the study showed that L. monocytogenes still had the potential to persist within multi-species biofilms, albeit in lower numbers than its cohabitants.
Testing the various biofilms against a PAA-based disinfectant, the researchers found that while no viable cells could be detected immediately after disinfection, substantial regrowth occurred after two, three, and four days in several specimens.
Remarkably, the disinfection treatment eliminated all single-species L. monocytogenes biofilms, but 15 out of 18 Pseudomonas biofilms and 13 out of 18 multi-species biofilms survived.
Additionally, L. monocytogenes persisted in 10 of the multi-species biofilms, further supporting the hypothesis that the properties of Pseudomonas in biofilm formation and disinfectant tolerance contribute to the survival of other pathogens like L. monocytogenes.
This study emphasizes the need to recognize the potential threat posed by Pseudomonas biofilms in food processing environments.
The ability of these biofilms to enhance the survival of Listeria monocytogenes, even after disinfection, underscores the importance of implementing effective measures to control and eradicate biofilm formation.
This discovery highlights the need to recognize Pseudomonas as a direct food safety hazard, as they can protect and shelter pathogens like L. monocytogenes.
Further research is needed to develop strategies that target and eliminate these resilient biofilms, thus ensuring food safety and reducing the risk of foodborne illnesses.
Related research in the field of food safety has focused on identifying effective strategies to combat biofilm formation and disinfectant tolerance.
Some promising approaches include the development of novel disinfectants and the use of antimicrobial coatings on food processing surfaces.
Furthermore, ongoing efforts are aimed at understanding the molecular mechanisms behind biofilm formation and the interactions between bacteria within these complex structures.
These advancements will contribute to the development of targeted interventions to mitigate the risks associated with biofilms in food processing environments.
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