An assessment by two European agencies has confirmed a Listeria outbreak from cold meat in the Netherlands and Belgium.

The European Food Safety Authority (EFSA) and European Centre for Disease Prevention and Control (ECDC) found people became sick between 2017 and August this year but were not able to link illness to a specific food source.

Twenty-one people were infected with Listeria monocytogenes IVb sequence type (ST) 6 in the Netherlands and Belgium. One person fell sick in October 2017, eight in 2018 and 12 in 2019.

Multiple sliced ready-to-eat (RTE) meat products from boiled and raw sausages from different suppliers produced between 2017 and 2019 by Offerman, a Dutch manufacturing company, were contaminated with Listeria that matched the outbreak strain.

Link to Offerman products
In August, the Netherlands reported a cluster of 18 invasive listeriosis cases to the Epidemic Intelligence Information System for Food- and Waterborne Diseases and Zoonoses (EPIS-FWD).

In October, the National Institute for Public Health and the Environment (RIVM) identified a cluster of 20 patients diagnosed with Listeria in the past two years. Three people died, all cases were hospitalized and one woman had a miscarriage. Two Dutch patients were pregnant women in their 30s. The others ranged in age from 64 to 94 years and 10 were men.

In the investigation, information on cases’ food exposure did not point towards a specific source. Of 19 Dutch patients, 15 had consumed cold meat products but reported eating different types of meat items.

With help from the Dutch Food and Consumer Product Safety Authority (NVWA) the outbreak was traced to RTE meat products from Offerman, a subsidiary of Ter Beke, and its site in Aalsmeer. The firm produces 650 different types of sliced RTE meat products for the retail market and catering industry and receives frozen and pre-packed sausages, about 200 different meat products, from 60 suppliers.

It was then revealed two people in Belgium had been infected with the same type of Listeria behind the outbreak in the Netherlands. The two patients were a 97-year-old woman and a Dutch mother diagnosed in Belgium.

Six products made from 2017 Listeria positive
Nine isolates from six sliced RTE meat products, produced between 2017 and 2019 by the Dutch company, were contaminated with a type of Listeria monocytogenes matching the outbreak strain, according to the EFSA and ECDC report.

“Although the exact points of contamination have not been identified yet, the results of the investigation suggest that the contamination may have happened at [Offerman], which represents the only common manufacturing point of the contaminated products.”

Other Listeria monocytogenes isolates from different serogroups were detected in 15 samples of RTE meat products prepared in 2019 and in four environmental samples collected at two sites within the Dutch company this year.

Following detection in food of Listeria monocytogenes isolates matching the outbreak strain, and discovery of environmental contamination with other Listeria monocytogenes strains, the Dutch company stopped production in October and withdrew and recalled all RTE meat products whose use-by-date had not yet past.

This action involved around 400 different types of sliced RTE meat based products corresponding to around 300 tons, and involved 10,000 food businesses located mainly in the Netherlands and Belgium.

Gaps in hygiene
Products were distributed to Aruba, Curaçao, Germany, Luxembourg, Sint Maarten, Spain, Suriname and the United Kingdom but none of these countries reported connected illnesses.

Official and own-check environmental sampling at the Dutch company detected Listeria monocytogenes ST 8 and ST 9 isolates from the equipment located in, or near the slicing lines, that did not match the outbreak strains or any Listeria isolated from meat products sampled.

However, inspections by Dutch authorities identified gaps in hygiene procedures in the company, which could have led to cross-contamination during production.

Some Listeria positive results do not list the amount of colony forming units per gram but one test from slicing line 1 in 2019 shows 270,000 cfu/g and another this year from line 5 was 15,000 cfu/g.

One isolate of Listeria monocytogenes IVb and ST 6 similar to the outbreak strain was detected in a sample of a RTE meat-based product also made by the Dutch company in August 2010.

Given the long incubation period of invasive listeriosis in some risk groups, possible delay in diagnosis and reporting, and in returning contaminated products to the point of sale, new cases may still be identified in the coming weeks or months, according to EFSA and ECDC.

“Therefore, specific attention should be paid to the administration of RTE meat products to people in hospitals, nursing homes and to those belonging to vulnerable population groups.”

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