Risks for public health related to the presence of Bacillus cereus and other Bacillus spp. including Bacillus thuringiensis in foodstuffs

Abstract

The Bacillus cereus group, also known as B. cereus sensu lato, is a subdivision of the Bacillus genus that consists of eight formally recognised species: B. cereus sensu stricto, B. anthracis, B. thuringiensis, B. weihenstephanensis, B. mycoides, B. pseudomycoides, B. cytotoxicus and B. toyonensis. The current taxonomy of the B. cereus group and the status of separate species mainly rely on phenotypic characteristics. Bacillus thuringiensis strains display a similar repertoire of the potential virulence genes on the chromosome as B. cereus sensu stricto strains and it has been shown that these genes can also be actively expressed in B. thuringiensis strains. Bacillus cereus and B. thuringiensis strains are usually not discriminated in clinical diagnostics or food microbiology. Thus, the actual contribution of the two species to gastrointestinal and non-gastrointestinal diseases is currently unknown. Most cases of food-borne outbreaks caused by the B. cereus group have been associated with concentrations above 105 CFU/g. However, cases of both emetic and diarrhoeal illness have been reported involving lower levels of B. cereus. The levels of B. cereus that can be considered as a risk for consumers are also valid for B. thuringiensis. There is no evidence that B. thuringiensis has the genetic determinants for the emetic toxin cereulide. The Panel has recommended the application of whole genome sequencing to provide unambiguous identification of strains used as biopesticides and the detailed characterisation of outbreak strains allowing discrimination of B. thuringiensis from B. cereus. Data gaps include: dose–response and behavioural characteristics of B. cereus group strains and specifically of B. thuringiensis. Field studies after application of B. thuringiensis biopesticides are needed to enable the establishment of pre-harvest intervals.