Introduction
Listeriosis outbreaks have been associated with a wide range of animal-derived foods, including unpasteurized milk, dairy products, raw or undercooked meat and raw or smoked fish products.
A survey conducted by Smartproteinproject (funded by the EU Horizon 2020) on European consumer attitudes towards plant-based foods has indicated an increasing consumption of plant-based food products in Europe over the years. In Belgium, there was an 8 % increase in sales volume between 2019-2020, with plant-based plain milk (primarily made from soy, almond and oat) showing the highest sales volume. Recently, a foodborne outbreak caused by L. monocytogenes was traced back to the consumption of almond-milk & cashew alternative to cheese. This report presents the first occurrence of such a matrix in listeriosis outbreaks in Belgium.
Materials and Methods
Food samples were collected by the Belgian Federal Agency for the Safety of the Food Chain (FASFC) and analysed at the National Reference Laboratory (NRL) for Foodborne outbreaks following ISO 11290 – 1 and – 2. A human strain was collected at the NRC Listeria. All isolated strains underwent serotyping for further characterisation at the NRC Listeria, and Whole Genome Sequencing (WGS) was performed for clustering analysis.
Discussion
Due to the growing demand for novel and alternative food products among the population, concerns are raised about the potential risks associated with plant-based food production. For example, challenge tests performed on bovine milk and plant-based milk demonstrated similar growth of L. monocytogenes. The outbreak described here provides strong evidence of the contamination of plant-based alternative to cheese with L. monocytogenes: the strain isolated from the affected individual (case) matched the strain found in the consumed vegan cheese-like product, indicating it as the source of contamination. A third isolate was obtained by analysing a different product of vegan alternative to cheese from the same brand, suggesting a potential contamination in the processing environment. The company has voluntarily implemented withdrawal and recall measures on all its cheese-like vegetable specialties (RASFF 2023.0500). Additional cases were also reported in Germany, France and The Netherlands (EpiPulse 2022-FWD-00102).
In conclusion, this report underscores the occurrence of L. monocytogenes in plant-based foods. It emphasizes the need for further investigation into the prevalence of this pathogen in plant-based foods and its survival throughout the plant-based food supply chain.
