An outbreak of listeriosis associated with baker’s yeast in Switzerland, 2022–2024

Horlbog et al. (Outbreak of listeriosis likely associated with baker’s yeast products, Switzerland, 2022–2024. Emerg Infect Dis. October 2024) from the Institute for Food Safety and Hygiene, Zurich, Switzerland, traced back a nationwide outbreak of human listeriosis in Switzerland to a persisting production line contamination of baker’s yeast contaminated with Listeria monocytogenes serotype 1/2a sequence type 3141, using WGS. The outbreak of listeriosis was prolonged and diffuse. The first case was reported in April 2022, and the outbreak peak occurred in 2023. The last known case was in June 2024. Of the 34 persons with documented cases, 7 died, and listeriosis was reported as the primary cause of death. All isolates of Listeria were genetically closely related (<2 allelic difference) to L. monocytogenes isolated from baker’s yeast (Saccharomyces cerevisiae) products from the commercial yeast factory and its production lines. The production lines revealed isolates of L. monocytogenes that matched the outbreak strain. The outbreak, linked to baker’s yeast, highlights the lack of data on the contamination of non-RTE products by L. monocytogenes and the need for manufacturers of baker’s yeast to consider this risk in their production processes. @ https://doi.org/10.3201/eid3011.240764

 Outbreak of Listeriosis Likely Associated with Baker’s Yeast Products, Switzerland, 2022–2024
Outbreak of Listeriosis Likely Associated with Baker’s Yeast Products, Switzerland, 2022–2024

Outbreak of Listeriosis Likely Associated with Baker’s Yeast Products, Switzerland, 2022–2024

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