Variation in growth of selected salt tolerant Listeria monocytogenes strains on Cold-Smoked Salmon
ORCID
0009-0007-9342-7423
Department
Biological Sciences
Year of Study
1
Full-time or Part-time Study
Full-time
Level
Postgraduate
Presentation Type
Poster
Supervisor
Michael Callanan
Supervisor
Maire Begley
Abstract
Background
Listeria monocytogenes is a psychotropic foodborne pathogen that can survive and grow in ready-to-eat (RTE) foods, including cold-smoked salmon. Its capacity to proliferate at refrigerated temperatures and withstand salt and acidic stress presents considerable food safety challenges. Consumption of contaminated products can lead to listeriosis, a severe sickness that predominantly impacts pregnant women, the elderly, and immunocompromised individuals. Although food regulations often regard L. monocytogenes as a homogeneous species, stress tolerance and growth characteristic variations between strains may pose a further food safety threat. Enhancing risk assessments and control methods for RTE seafood requires an understanding of how various strains respond to actual storage conditions
Aims
This study aimed to evaluate the growth behaviour of L. monocytogenes strains with differing salt tolerance in cold-smoked salmon stored at 4°C, 10°C, and 20°C. The goal was to determine how strain variability and storage temperature influence the pathogen’s growth potential in RTE seafood.
Methods
Based on their characteristics of stress tolerance, three strains of L. monocytogenes were chosen. Cold-smoked salmon was cut into 10 g portions and inoculated with 100 µL of bacterial suspension (3 to 4 log CFU/g). Samples were stored at 4°C for 30 days, 10°C for 12 days, and 20°C for 6 days. At selected intervals, samples were homogenized in Buffered Peptone Water and plated on Oxford Listeria Agar for enumeration. Growth rates were determined based on observed bacterial counts using ComBase predictive modelling tools.
Results
Significant differences in growth rates were observed among strains at 4°C and 10°C. High salt-tolerant strains showed faster growth compared to the low-tolerant. In contrast, at 20°C, all strains exhibited similar growth rates, suggesting that elevated temperatures reduce the impact of tolerance differences.
Conclusion
Strain variability plays a key role in L. monocytogenes behaviour at lower temperatures, which has implications for food safety and shelf-life estimation. These findings support the need for incorporating strain-specific data into risk assessments for smoked salmon. It also provides valuable insights for food producers and regulators to better control L. monocytogenes in smoked salmon and similar products.
Keywords:
L.monocytogenes, Salt Tolerance, Strain Variability, Smoked Salmon, Predictive Microbiology
Start Date
16-6-2025 11:00 AM
End Date
16-6-2025 12:00 PM
Recommended Citation
Butt, Waleed, "Variation in growth of selected salt tolerant Listeria monocytogenes strains on Cold-Smoked Salmon" (2025). ORBioM (Open Research BioSciences Meeting). 2.
https://sword.mtu.ie/orbiom/2025/shorttalk/2
Variation in growth of selected salt tolerant Listeria monocytogenes strains on Cold-Smoked Salmon
Background
Listeria monocytogenes is a psychotropic foodborne pathogen that can survive and grow in ready-to-eat (RTE) foods, including cold-smoked salmon. Its capacity to proliferate at refrigerated temperatures and withstand salt and acidic stress presents considerable food safety challenges. Consumption of contaminated products can lead to listeriosis, a severe sickness that predominantly impacts pregnant women, the elderly, and immunocompromised individuals. Although food regulations often regard L. monocytogenes as a homogeneous species, stress tolerance and growth characteristic variations between strains may pose a further food safety threat. Enhancing risk assessments and control methods for RTE seafood requires an understanding of how various strains respond to actual storage conditions
Aims
This study aimed to evaluate the growth behaviour of L. monocytogenes strains with differing salt tolerance in cold-smoked salmon stored at 4°C, 10°C, and 20°C. The goal was to determine how strain variability and storage temperature influence the pathogen’s growth potential in RTE seafood.
Methods
Based on their characteristics of stress tolerance, three strains of L. monocytogenes were chosen. Cold-smoked salmon was cut into 10 g portions and inoculated with 100 µL of bacterial suspension (3 to 4 log CFU/g). Samples were stored at 4°C for 30 days, 10°C for 12 days, and 20°C for 6 days. At selected intervals, samples were homogenized in Buffered Peptone Water and plated on Oxford Listeria Agar for enumeration. Growth rates were determined based on observed bacterial counts using ComBase predictive modelling tools.
Results
Significant differences in growth rates were observed among strains at 4°C and 10°C. High salt-tolerant strains showed faster growth compared to the low-tolerant. In contrast, at 20°C, all strains exhibited similar growth rates, suggesting that elevated temperatures reduce the impact of tolerance differences.
Conclusion
Strain variability plays a key role in L. monocytogenes behaviour at lower temperatures, which has implications for food safety and shelf-life estimation. These findings support the need for incorporating strain-specific data into risk assessments for smoked salmon. It also provides valuable insights for food producers and regulators to better control L. monocytogenes in smoked salmon and similar products.