EHEC germs on Spanish cucumbers do not correspond to the pathogen type of the patients concerned
A virulent EHEC strain O104:H4 is responsible for the current outbreak of EHEC infections. At the Hamburg-based Institute for Hygiene and Environment cucumbers from Spain were identified as EHEC carriers. These samples have been more thoroughly examined by the National Reference Laboratory for E. coli of the Federal Institute for Risk Assessment (BfR). None of the four samples showed the serotype O104:H4 of the pathogens which had been isolated from the faeces samples of the patients. “The source of the on-going infections has not yet been determined”, says BfR President Professor Dr. Dr. Andreas Hensel. “Furthermore, it has to be clarified at what point in the food chain the contamination with germs occurred.”
EHEC are difficult to identify since these bacteria are not different from innocuous E.coli bacteria of the intestinal flora in terms of their general properties. In order to safely identify EHEC, it is, therefore, necessary to determine Shiga toxins and/or verotoxins, other typical EHEC properties and the serotype.
The epidemiological tests carried out so far by the Robert Koch Institute suggest that the recent infections by EHEC have been caused with a high probability by the consumption of raw tomatoes, cucumbers and salads. Last week the Hamburg-based Institute for Hygiene and Environment (HU) of the Health and Consumer Protection Agency identified cucumbers from Spain as EHEC carriers. However, the Hamburg institute has not been able to show in the two samples examined so far a correspondence with the pathogens of the type O104:H4 isolated from the faeces samples of the patients. The National Reference Laboratory for E. coli at the Federal Institute for Risk Assessment has been provided with four samples to type the pathogens.
The National Reference Laboratory has determined the pathogen type of the samples made available by using a validated specific and rapid method (real time PCR). The method tests simultaneously for Shiga toxin genes and the O104 gene.
For all four samples no EHEC O104:H4 was detected. In two of the four samples Shiga toxin-forming E. Coli of a different serotype were found.
As long as the source of the on-going infections has not been identified beyond doubt and closed, consumers are requested to take every precaution. It is not yet clear where the contamination with germs occurred in the food chain. Regardless of that, BfR recommends, by way of precaution, to continue not the consume tomatoes, cucumbers and salads raw.
All persons with diarrhea should ensure that strict hand hygiene is observed, in particular vis-à-vis infants and immunodeficient persons. The recommendations on good kitchen hygiene, as published by BfR in its leaflet to avoid EHEC infections, continue to apply.
The Federal Institute for Risk Assessment (BfR) is a scientific institution within the portfolio of the Federal Ministry of Food, Agriculture and Consumer Protection (BMELV). It advises the Federal Government and Federal Laender on questions of food, chemical and product safety. BfR engages in own research on topics that are closely linked to its assessment tasks.