E. coli infection and consumption of sprouts: ANSES reviews existing knowledge and issues recommendations for further research
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News of 12/07/2011
12 July 2011
As of 22 June 2011, cases of bloody diarrhoea and haemolytic-uraemic syndrome (HUS) occurred in adults, mostly women, in the Bordeaux area. These people were infected by a strain of Escherichia coli belonging to the serotype O104:H4, a bacterium which is genetically related to that responsible for the epidemic reported in Germany in May 2011. The epidemiological investigation conducted in France quickly identified the source of this contamination as being the consumption of sprouts (fenugreek sprouts in particular) at a local fair in early June.
The clustering of the outbreaks in Germany and then in France and the points they have in common (involving the same strain of bacteria, rarely found up to now in cases of food poisoning, and also the same suspected origin of the sprouts) led the investigators to suppose that there was a common source of contamination. A trace-back study, coordinated by the European Food Safety Authority (EFSA) revealed that there was a link with the consumption of seeds imported from Egypt (report published on 5 July 2011)(1).
On 5 July 2011, the European commission decided to withdraw from the market, then analyse and destroy all of the batches of fenugreek seeds imported into Europe between 2009 and 2011 by an Egyptian exporter. This decision also included the suspension through 31 October 2011 of imports of Egyptian seeds and beans intended for sprouting (2).
In this context, ANSES issued a formal internal request for a review of current knowledge in relation to the Bordeaux outbreak and its points in common with the German outbreak. Accordingly, the Agency set up a working group made up of experts from its laboratories as well as from the National Reference Laboratory (Vet-AgroSup, Lyon), the National Reference Centre (Institut Pasteur, Paris) and its affiliated laboratory (CHU Robert Debré, Paris), the French Institute for Public Health Surveillance (InVS), the French National Institute for Agricultural Research (INRA - Avignon and Angers) and the Group for the study and control of varieties and seeds (GEVES) as well as the INSERM1043 unit at the National Veterinary School in Toulouse.
The Opinion published today describes the main elements that are known about the pathogenic bacterium involved, its detection in the seeds and the corresponding epidemiological data. It reviews the current epidemic and highlights the key stages to be taken into account when producing sprouts as well as the possible sources of contamination at different stages of the production process.
At the current time, the bacterium identified in patients (Escherichia coli O104:H4) has not yet been detected in the seeds themselves. It is in fact especially difficult to detect pathogenic bacteria in dry substrates such as seeds, since bacteria in this state are stressed, making their revival, proliferation, and subsequent identification particularly complex. Moreover, a very small amount of the bacteria can cause an infection. Consequently, the fact that no pathogenic bacteria have yet to be detected in the samples analysed does not necessarily mean that the batches of seeds have not been contaminated.
ANSES therefore recommends continuing to screen for the bacteria in the seeds by means of different detection protocols used in tests in the various laboratories involved in France and in Europe, as well as collecting enough batches of potentially contaminated seeds throughout Europe to enable the tests to continue.
ANSES has also identified the need to better characterise the incriminated O104:H4 strain and more specifically the ability of the bacteria to survive in seeds as well as their ability to adhere to surfaces (depending on the environment and the nature of the material in question).
ANSES also recommends a more thorough evaluation of sprouting practices under industrial conditions. This would involve
- evaluating the impact of the sprouting practices involved and the effect of temperature on the survival and proliferation of pathogenic shiga toxin-producing Escherichia coli (STEC) in particular;
- evaluating the effectiveness of cleaning and disinfection measures applied to surfaces and raw materials, with respect to these strains and in relation to the elements highlighted in the Opinion:
- developing methods for detecting pathogenic STECs in seeds or during the sprouting process in order to optimise batch controls.
Finally, as far as the consumption of sprouts is concerned, ANSES reiterates the recommendations issued by the European Food Safety Authority (EFSA) and French authorities, namely to not consume raw sprouts (which should be cooked at a high temperature, in other words at 70° C for 2 minutes). Consumers are also advised to not grow seeds for their own consumption. These recommendations may be revised following the epidemic outbreak (i.e. approximately 30 days after the reporting of the last case), in the light of knowledge acquired.
(1) European Food Safety Authority; Tracing seeds, in particular fenugreek (Trigonella foenum-graecum) seeds, in relation to the Shiga toxin-producing E. coli (STEC) O104:H4 2011 Outbreaks in Germany and France. Question No EFSA-Q-2011-00817, issued on 5 July 2011.http://www.efsa.europa.eu/en/supporting/pub/176e.htm, accessed on 5 July 2011.
(2) http://europa.eu/rapid/pressReleasesAction.do?reference=IP/11/831&format=HTML&aged=0&language=FR&guiLanguage=en, accessed on 5 July 2011.
Find out more
> Opinion of 7 July 2011 on the current state of scientific knowledge and information available for making recommendations, following the onset of several cases of haemolytic-uraemic syndrome (HUS) observed in France in June 2011 and suspected of being related to the consumption of sprouts
> Our news update of 29 June 2011