EFSA Issues Advice to Mitigate Risks from Possible Exposure to STEC in Vegetables

The European Food Safety Authority (EFSA) has published its fast-track risk assessment on consumer exposure to STEC/VTEC (Shiga toxin- or verotoxin-producing E. coli) through the consumption of raw vegetables and provided advice on options to mitigate the risks of possible food contamination and human infection. The strain (STEC O104:H4) responsible for the current outbreak in Germany, although rare, is similar to strains that have been previously reported.

Currently, the route of exposure for the STEC outbreak in Germany remains unknown. While contamination of fresh vegetables with STEC is rare, it has been associated with some severe outbreaks, including the current outbreak in Germany. The European Commission has therefore requested EFSA to provide advice on the relative exposure of humans to STEC from surface or internal contamination of vegetables and from the handling of vegetables from the farm to the consumer. Due to limited information available regarding STEC in vegetables, EFSA scientists were unable to estimate the relative human exposure through these routes. With respect to risk mitigation, EFSA scientists highlight the importance of preventing contamination before and after harvesting.

EFSAs scientists assessed that the strain responsible for the outbreak in Germany is similar to strains that have been previously reported. However, in the current outbreak, this strain is responsible for an unusually high number of people affected and an increased severity of illness. Infection with STEC can cause bloody diarrhoea and can lead to cases of haemolytic uremic syndrome (HUS) in humans; a systemic disease which can in some cases result in acute kidney failure and fatalities.

Humans can be exposed to STEC and eventually become infected through contaminated food and water, direct or indirect contact with animals or human-to-human contact. In this report, EFSA has specifically assessed possible exposure through vegetables.

In its exposure assessment, EFSA considered bacterial contamination on the surface as well as inside the vegetable both before and after harvesting. While the overall prevalence of vegetable contamination with STEC at EU level is very low, there is a growing number of reports in the international scientific literature of STEC outbreaks associated with vegetables, particularly sprouting seeds and green, leafy salad vegetables. Contamination occurs mostly on the surface of plant tissues. However, internal contamination, such as through the root of the plant, cannot be ruled out although the data to support this are very limited and of an experimental nature.

As requested by the European Commission, EFSAs scientists make recommendations for mitigating the possible risks of food contamination and human infection from STEC. EFSA confirms existing advice on the importance of following good agricultural practices, and good manufacturing and hygiene practices as laid down in internationally recognised guidelines.

In addition to this work, EFSA is supporting the STEC outbreak investigation by providing senior scientific staff with expertise in data collection, and epidemiological analysis including foodborne outbreaks.