Hendrik Frentzel
German Federal Institute for Risk Assessment, Germany
Title: Presumptive Bacillus cereus/Bacillus thuringiensis in vegetable food: natural contaminant or pesticide residue?
Biography
Biography: Hendrik Frentzel
Abstract
The Bacillus (B.) cereus group (also called B. cereus sensu lato or presumptive B. cereus) currently comprises eight closely related species which are difficult to differentiate and are thus not distinguished in routine diagnostics. However, the potential to cause foodborne disease differs between these species. Especially, B. cereus and B. cytotoxicus are considered foodborne pathogens whereas discussions on the pathogenic potential of B. thuringiensis are ongoing. Presumptive B. cereus is common contaminants of vegetable food, while the individual B. cereus group species with its toxinogenic potential remains mostly unknown. A possible unnatural source of contamination is the application of B. thuringiensis based biopesticides. Still, evidence for biopesticide residues on food is scarce. This lack of evidence was also noted by the EFSA Panel on Biological Hazards in a Scientific Opinion of 2016. In order to address these issues, we analyzed samples of spices, dried and fresh herbs, and bell pepper for presumptive B. cereus. Additionally, tomato and sprout samples were analyzed by food inspection laboratories of the federal states in Germany. Obtained isolates were further characterized in terms of species affiliation, toxinogenic potential and partially their multilocus sequence type (MLST). The presumptive B. cereus prevalence and contamination levels ranged from 8 to 95% and from 101 to 104 cfu/g. Most strains were able to produce toxins. The presumptive B. cereus populations from bell pepper and tomatoes were dominated by B. thuringiensis (93% and 99%, respectively). These strains were indistinguishable from the biopesticide B. thuringiensis subsp. aizawai ABTS 1857 or B. thuringiensis subsp. kurstaki ABTS-351, respectively, based on the following parameters: toxin genes, toxin production, cry1 gene and parasporal crystal content as well as MLST profiles. These findings indicate that the B. thuringiensis burden in the analyzed bell pepper and tomato samples may originate from residues of biopesticides.