Occurrence and identification of Bacillus thuringiensis in fresh vegetables and fruits in France

Bacillus thuringiensis (Bt)-based plant protection products are among the most widely used biopesticides in the world, thereby reducing the use of synthetic pesticides in the interest of limiting potential environmental toxicity or pollution. However, recent concerns about food safety call for better characterization of the potential risk associated with Bt and thus an estimation of exposure to this spore-forming bacterium through food. Here, we made an inventory of the use of Bt-based products in France and then carried out a prevalence study on 159 organic fruit and vegetable samples. Our results revealed the presence of Bt in half of the samples, with colony counts ranged from 10¹ CFU/g to 9.6 × 10⁴ CFU/g (average level of 4.3 × 10³ CFU/g). In addition, we determined genomic markers specific to Bt strains approved in Europe, making it possible to identify 90 % of the Bt isolates analysed. Finally, washing assays on tomatoes highlighted the strong adhesion and persistence of Bt spores on the food matrix, and the need to use sporicidal agents to significantly reduce the bacterial load on this type of food. This work will therefore contribute to better monitoring and characterization of the risks associated with the use of Bt in agriculture, with the aim of making its use as safe as possible for consumers.