Guidance on the assessment of the toxigenic potential of Bacillus species used in animal nutrition

Bacillus species are used in animal production directly as microbial feed additives or as the source of other feed additives, notably enzymes. The principal safety concern for consumers and, to a lesser extent livestock, associated with Bacillus is a capacity for toxin production. However, the capacity for toxin production and the nature of the toxins produced is unevenly distributed over the genus, occurring frequently in some species and more rarely in others. In principle, the selection of strains belonging to the B. cereus taxonomic group for direct use in animal production is considered inadvisable. If, however, they are proposed then the full genome should be sequenced and a bioinformatic analysis made to search for genes coding for enterotoxins and cereulide synthase. If there is evidence of homology, the non-functionality of the genes (e.g. mutation, deletion) must be demonstrated. For other species, concerns appear to be associated to the production of surfactin like-lipopeptides, although the relation between the presence of these compounds and/or other toxic factors and the risk of illness in human has not yet been established. In the absence of animal models shown to be able to distinguish hazardous from non hazardous strains, the FEEDAP Panel relies on the use of in vitro cell-based methods to detect evidence of a cytotoxic effect. Such tests should be made with culture supernatants since the concentration of cells obtained in a broth culture would always exceed that found in animal food products. If the strain proves to be cytotoxic it is not recommended for use.