A proposed system in Switzerland should help with Listeria control and outbreak investigations, according to researchers.
Swiss monitoring and control of food for Listeria monocytogenes, as well as data collection, takes place on several levels. Because of a complex legal framework, the Federal Food Safety and Veterinary Office (FSVO) has issued guidance. Certain data is not directly accessible between agencies without additional steps because of data protection.
A new genomic national information system is planned, which will enhance outbreak investigations and improve the prevention and control of listeriosis. It will allow standardized comparisons of isolates from humans, food, animals, and the environment, enabling integrated outbreak investigations, cross-agency data sharing, and timely public health responses, said researchers.
A review of listeriosis in the country collected epidemiological data, data on official sampling, reporting and outbreaks from government agencies and other sources. Results were published in the Journal of Consumer Protection and Food Safety.
Risk from non-RTE food
Between 2015 and 2024, on average 53 listeriosis cases were reported annually, with the highest rates in adults over 65 and children younger than 1 year old. Official sampling found Listeria monocytogenes most commonly in meat and meat products, ready-to-eat foods, and fish products.
Cases in Switzerland and Liechtenstein ranged from 33 in 2021 to 78 in 2022. In the same period, 627 positive samples were recorded with 597 from food and 30 from food business environments. There were 25 recalls and 36 public warnings. Most involved cheese, followed by ready meals, snacks and fish.
Since 2022, an outbreak linked to non-ready-to-eat baker’s yeast has 39 confirmed cases with six in 2022, 24 in 2023, eight in 2024, and one in 2025. Eight deaths have been reported across 14 cantons. The outbreak strain was isolated from various foods, not only yeast, suggesting cross-contamination.
Scientists said national legislation should be expanded to address cross-contamination risks posed by non-RTE items. They added that limits for Listeria in non-RTE products, and requirements for environmental sampling at food companies are lacking, and a revised legal approach is needed to address these gaps.
Bacillus cereus outbreak
A different study has reported on a Bacillus cereus outbreak that sickened almost 30 children. Researchers found inadequate temperature control during food holding.
In September 2025, the Cantonal Laboratory of Basel City received reports of vomiting following consumption of food served at a school canteen. Most pupils reported eating “Älplermagronen,” a traditional Swiss macaroni dish similar to macaroni cheese.
The outbreak involved 27 children, and symptoms started 40 to 90 minutes after lunch. Severity and duration of symptoms correlated with the amount of food eaten but no patients required medical treatment.
Retention samples of the macaroni dish had not been stored, but microbiological analyses of food from the kitchen revealed the presence of Bacillus cereus in leftovers of a béchamel sauce that was an ingredient of the macaroni dish, according to the study published in the Journal of Food Protection.
The macaroni dish had been made four days prior to the outbreak and was part of the lunch menu the day after preparation. Reheated food was placed in hot containers for serving. However, temperature control was not in place and potentially remained outside the safe limits of 60 degrees C (140 degrees F) for several hours.
Leftovers were shock-frozen and stored over the weekend to be reheated with the béchamel sauce and served in the canteen again. Prolonged storage at inadequate temperature likely led to Bacillus cereus proliferating and producing toxins.
“This outbreak highlights the importance of respecting strict storage conditions and maintaining time-temperature control in the handling of hot ready-to-eat cooked foods served in canteens to mitigate the hazards pertaining to Bacillus cereus,” said scientists.”
Author: Joe Whitworth
Source: Food Safety News
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