Controlling Listeria monocytogenes in the food processing environment: Lessons learned from a salmon processor...

Area of Science:

• Food Microbiology
• Food Safety
• Bacterial Pathogenesis

Background:

• Listeria monocytogenes causes listeriosis, a severe illness often associated with ready-to-eat foods like cold-smoked salmon.
• Specific strains, such as L. monocytogenes ST121, have been linked to significant foodborne illness outbreaks.
• Persistent contamination in food processing environments poses a continuous risk to public health.

Purpose of the Study:

• To identify the sources of L. monocytogenes ST121 contamination in a cold-smoked salmon processing facility.
• To evaluate the effectiveness of various mitigation strategies, including cleaning, disinfection, and equipment replacement.
• To assess the role of whole genome sequencing (WGS) in tracking and resolving persistent bacterial contamination.

Main Methods:

• Conducted a 11-week 'Seek and Destroy' investigation involving environmental and product sampling.
• Utilized whole genome sequencing (WGS) to analyze 37 L. monocytogenes isolates.
• Implemented and evaluated multiple decontamination methods, including chemical disinfection, heat treatment, and equipment replacement.

Main Results:

• The skinning machine, particularly its conveyor belts and roller, was identified as the primary reservoir for the outbreak strain.
• Standard cleaning, disinfection, and heat treatments were insufficient to eradicate contamination.
• Replacement of the skinning machine, coupled with enhanced sanitation, successfully eliminated L. monocytogenes from the facility.
• WGS confirmed the persistence of ST121 and linked environmental isolates to the outbreak strain.

Conclusions:

• Hygienic design of food processing equipment, especially the skinning machine, is critical for preventing persistent contamination.
• Effective control of L. monocytogenes in RTE seafood processing requires a multi-faceted approach, including equipment modification and rigorous sanitation.
• WGS is an invaluable tool for identifying sources and confirming the elimination of persistent foodborne pathogens.