Listeria traced to Hjerting Laks despite fish products passing tests

DVFA has linked Hjerting Laks to the outbreak but said all products have tested below the acceptable limit for Listeria

Four people have been sickened by Listeria linked to a fish producer in Denmark but authorities have not found high levels of the pathogen in products on the market.

Fødevarestyrelsen (The Danish Veterinary and Food Administration) said intensive sampling and testing for Listeria at Hjerting Laks has not revealed any products with elevated levels.

There has been no product recall because tested samples have been below the accepted limit.   

Company link due to DNA match

Annette Perge, head of unit in the DVFA said the outbreak has been traced to Hjerting Laks as it has a DNA match between samples from the company and patients.

“In Denmark, Listeria isolates from patients and official food samples are typed using whole genome sequencing,” she told FoodQualityNews.

“This gives us an excellent opportunity to find sources of outbreaks. In this case, we have a DNA match between Listeria from the patients and samples taken from the company’s production area and equipment.

“Further on, patients’ consumption of products prior to illness and their shopping habits fit with products and distribution from the company.

“Finally, the specific Listeria monocytogenes ST6 sequence pattern in question has not been detected in other samples from other sources.

“We see other ST6 sequences in other products and patients but not this exact sequence.”

In May, FQN reported two people were diagnosed with the same Listeria strain which caused 40 cases and 16 deaths last year from deli meat, as part of an investigation of five sick people.

The current outbreak involves Listeria monocytogenes ST6 and is not linked to the outbreak last year.

However, one case of the five mentioned is part of the outbreak traced back to the establishment Hjerting Laks thanks to work by DVFA, Statens Serum Institut and the National Food Institute.

The first person became ill at the beginning of April, the second in mid-May, the third in mid-June and the fourth at the end of June.

Hjerting Laks response and past outbreak

DVFA said it did not know exactly which food item caused the outbreak but suspects smoked salmon, since patients have eaten this product prior to illness.

Hjerting Laks said samples this year of final products have met all requirements, the bacteria could originate from raw materials delivered to other processors and the link to it is made despite the small case number.

The firm was connected with a minor outbreak of Listeria late last year related to smoked halibut which was stopped by changing some of the production processes.

No further cases related to smoked halibut have been seen since November 2014, said DVFA.

Perge said due to the incident last year DVFA has strengthened control of Listeria at the company, which co-operated throughout the process.

We have ordered the company to change its routines with regards to production and own-check scheme. This includes upscaling their analyses program. We have placed the establishment under tightened supervision for the time being and until we know if the new procedures in place are effective.

“We advise people to throw away products that have exceeded the “use by” date, to keep the refrigerator temperature below 5 degrees C, to remember that a product’s shelf-life shortens upon opening the packing and to remember the general advices on good hygiene in the kitchen.” 

In Denmark about 50 cases of illness due to Listeria bacteria are registered a year. But in 2009 and 2014 there were 90 to 100 due to major outbreaks. This year has the count is at 25 registered cases.   

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