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Public health risks of the Bacillus cereus group

Public health risks of the Bacillus cereus group

From 2007 to 2014, EU Member States reported 413 strong-evidence foodborne outbreaks associated with the naturally occurring, soil-borne bacteria Bacillus cereus, which affected 6,657 people and caused 352 hospitalisations.

Bacillus cereus group is very diverse and that there was little information in the literature on other pathogenic Bacillus spp. The Bacillus cereus group comprise eight recognised species and it includes the opportunistic pathogen B. cereus sensu stricto, which is frequently implicated in cases of food poisoning, the entomopathogen B. thuringiensis, from which a number of selected strains are widely used as biopesticides, and the causative agent of anthrax B. anthracis. B. 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. The levels of B. cereus that can be considered as a risk for consumers are also valid for B. thuringiensis.

Several B. thuringiensis strains have been approved as plant protection active substance in Europe and other strains are under evaluation. As no specific Maximum Residue Level (MRL) was fixed for these active substances under Reg. (EC) No 396/2005, the default MRL of 0.01 mg/kg is applicable to all food products. However, this value is currently under discussion at the pesticides residues section of the Standing Committee for Plants, Animals, Food and Feed.

The EU Biological Hazards (BIOHAZ) Panel recommends to:

  • Obtain information through whole genome sequencing in order to provide unambiguous identification of strains used as biopesticides and assist further safety assessment.
  • In cases of food-borne outbreaks associated with the cereus group, characterise strains in detail allowing discrimination of B. thuringiensis from B. cereus, as well as the identification of strains related to commercial B. thuringiensis used as biopesticides.
  • Maintain cereus group food-borne outbreak strains in accessible culture collections preferentially managed by reference laboratories.
  • Identify markers for commercial thuringiensis strains to allow regular monitoring and easy differentiation in suspect outbreak situations.
  • Promote field studies after application of thuringiensis biopesticides in order to inform the possible establishment of pre-harvest intervals.
  • Develop research on dose–response and behavioural characteristics of cereus group strains and specifically of B. thuringiensis, to facilitate risk characterisation.
  • Develop studies to monitor and characterise the factors that lead to/favour the transfer of the cereus group and specifically B. thuringiensis from the environment to foodstuffs and identify the routes and critical steps of contamination in the food industry.

For further information, please refer to:

EFSA Journal, Volume 14, Issue 7, July 2016

Photo credit: Kanijoman via / CC BY

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