Scientific Opinion on the Risk Posed by Shiga Toxin-producing Escherichia Coli (STEC)

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The European Commission asked the Panel on Biological Hazards to issue a scientific Opinion on the public health risk of Shiga toxin-producing E. coli (STEC) and other pathogenic bacteria that may contaminate seeds and sprouted seeds and in particular the Panel was asked: to assess the public health risk caused by STEC and other pathogenic bacteria that may contaminate both seeds and sprouted seeds intended for direct human consumption.

The BIOHAZ Panel was also asked: to the extent possible, to identify risk factors contributing to the development of STEC and other pathogenic bacteria that may contaminate these seeds and sprouted seeds; (iii) to recommend possible specific mitigation options, and to assess their effectiveness and efficiency to reduce the risk throughout the food chain (from the seed production until final consumption); and lastly, (iv) to recommend, if considered relevant, microbiological criteria for seeds and sprouted seeds, water, and other material that may contaminate the seeds and sprouts throughout the production chain.

Sprouted seeds are young seedlings obtained from the germination of seeds. They are ready-to-eat foods which have caused large outbreaks. The bacterial pathogens most frequently associated with illness due to contaminated sprouted seeds are Salmonella and to a lesser extent STEC. Bacillus cereus, Listeria monocytogenes, Staphylococcus aureus and Yersinia enterocolitica have also been transmitted by sprouted seeds, albeit very rarely.

Dry seed contaminated with bacterial pathogens has been identified as the most likely initial source of sprout-associated outbreaks; although other routes of contamination (e.g. during production due to poor practices) may also occur. In some outbreaks, contamination of seeds with as low as 4 Salmonella per kg was sufficient for the sprouts to cause disease.

Seeds purchased by sprouts producers are usually not grown specifically for this purpose. They may be contaminated during production, harvest, storage and transport, and there may be difficulties in traceability of seeds from production to sprouting. Bacterial pathogens on seeds may survive for long periods during seed storage.

There is so far no guarantee of a bactericidal step which is able to control contamination of seeds with bacterial foodborne pathogens acquired prior to germination. Due to the high humidity and the favourable temperature during sprouting, bacterial pathogens present on dry seeds can multiply on the sprouts.

Contamination with pathogenic bacteria must be minimized by identification of seed crops intended for sprouted seeds production before planting, and application of GAP, GHP, GMP, HACCP principles at all steps of the production chain. The relevance of decontamination treatments of seeds and of microbiological criteria is also discussed.

More information and the opinion may be found on the EFSA Website.