Repeated incidents of raw meat products as a source of infection shows the importance of risk awareness when handling or consuming such items, according to Dutch researchers investigating a Salmonella outbreak that sickened 46 people in 2015.
Researchers said adding information on food packaging would allow consumers to make informed decisions when consuming risk products.
“Similar to already implemented mandatory provision of allergen information on food product labels – we recommend adding explicit warning labels to food products that could potentially be microbiologically unsafe for consumers, especially meat products that are eaten raw or undercooked,” they added.
Based on microbiological and epidemiological evidence, beef sold as filet américain and minced beef was the source of infection in the 2015 outbreak. In the Netherlands, filet américain was the likely vehicle of infection in three previous Salmonella Typhimurium outbreaks.
In October 2015, six related cases with gastroenteritis called the Netherlands Food and Consumer Product Safety Authority (NVWA). They suspected filet américain, a bread spread consisting of finely chopped raw beef mixed with a herb sauce, to be the source of infection.
Leftovers and stool samples tested positive for Salmonella Typhimurium. An increase of this strain was observed in national Salmonella surveillance, revealing 46 cases between 26 October and 9 December.
Cases identified through the national surveillance (n=40) were distributed across the country. The majority of laboratory-confirmed cases were female (58 percent) and ages ranged from two to 79 years. One third of cases were nine years or younger.
“As the very young, elderly, pregnant and the immunocompromised are known to be at greatest risk of severe disease and death in relation to food- and waterborne infections, these vulnerable groups should abstain from eating raw or undercooked meat products,” according to the study.
In the Netherlands, salmonellosis is only notifiable in case of a cluster with two or more cases probably linked to contaminated food or drinking water. Annually, 15-20 Salmonella outbreaks are detected in the country.
Salmonella Typhimurium with MLVA pattern 02-23-08-08-212 had not been previously detected in the country.
An urgent inquiry was made on the Epidemic Intelligence Information System for Food- and Waterborne Diseases and Zoonoses (EPIS-FWD) operated by the European Centre for Disease Prevention and Control (ECDC) but this yielded no clues for solving the outbreak.
Of twenty nine cases who filled in a questionnaire, eight were hospitalized.
Consumption of filet américain was most often reported (76 percent), followed by minced beef (55 percent). In total 26 cases ate one or both products in the week before illness.
Twenty cases purchased meat products as part of grocery shopping at a supermarket, two bought meat exclusively at the butcher and seven cases bought it at both venues.
The six local cluster cases purchased filet américain at a supermarket chain. This unnamed store produced filet américain locally by mixing prepared ground beef and a ready-made herb sauce. Inspection of the local production site did not reveal any breach of hygiene standards.
The supermarket was supplied meat by a producer who distributed raw material from a Dutch deboning plant. This plant had processed around 58 tons of meat parts on a day in October 2015, originating from six slaughterhouses from four different European countries. The deboning plant delivered about 46 tons of meat for human consumption to 55 meat-processing plants; of these, 32 were in eight other EU member states.
“The identified batch is the production of one day in the deboning plant. It is therefore likely that the batch will not be contaminated completely or evenly due to a point source contamination of one or more carcasses. Secondly, the number of cases will be an underestimation as most people with gastroenteritis do not visit a physician or are not tested,” said researchers.
Links were established between the Dutch deboning plant and suppliers of three other supermarket chains, a diner and delicacy shop.
As the contaminated 46-ton batch of beef was mixed with meat from other parties at various customers, the contaminated batch amounted to 400 tons. Of this, around 65 tons were classed as risk products defined as “ready to eat” or items very likely to be consumed with treatment insufficient to eliminate or reduce risk of Salmonella infection to an acceptable level based on consumers’ consumption habits.
Most risk products had been sold and/or the best before date had expired. About one ton was still available and was withdrawn to prevent further cases.
Samples of filet américain and separate samples of sauce and raw meat to be used for filet américain were taken at the producer. They were from other batches than the incriminated one and tested negative for Salmonella spp.
Researchers said to ensure food safety batches of products intended to be eaten without sufficient heat treatment, should be submitted to risk based HACCP procedures to verify compliance with regulations.
“If such standards are not met – or as a general part of the production process – pre-treating risk products prior to sale could be considered,” they added.