Profile on “STEC / VTEC / EHEC”
General Information and Origin
Some strains of Escherichia coli, such as STEC (Shiga toxin-producing Escherichia coli), VTEC (Verotoxin-producing Escherichia coli), or EHEC (Enterohaemorrhagic Escherichia coli), can cause severe foodborne illnesses. In addition to the classic gastrointestinal symptoms of food infections and intoxications (vomiting, diarrhea, fever, …), diseases caused by EHEC strains can lead to HUS syndrome (hemolytic-uremic syndrome) resulting in kidney failure and death.
These dangerous bacteria often occur in the intestines of ruminants (especially cattle, but also, for example, sheep and goats). They can be transmitted to humans through food, as well as through direct contact, for example, in petting zoos.
Significance
The presence of these pathogenic Escherichia coli strains in ready-to-eat foods is undesirable and considered a potential health hazard. Since these infections can sometimes have severe, life-threatening consequences, including death, these pathogens are feared in food. Appropriate measures must be taken when viable STEC/VTEC is detected in ready-to-eat foods. Often, the cause of contamination with these microorganisms is fecal contamination, but due to their longer survival rate in the environment (e.g., in soil), different contamination causes must be considered situationally (see the paragraph below). In addition to raw animal products, these bacteria are also regularly detectable in raw plant foods. Affected foods include raw milk, raw beef, and raw milk cheese, as well as ready-to-eat sprouts and various mixed and leafy salads, and freshly squeezed fruit juices.
Important Causes for Elevated Bacterial Counts
- Fecal or cross-contamination during the slaughtering process
- Contamination of raw animal products, e.g., raw milk and plant-based foods
- Use of contaminated raw materials, e.g., in the production of raw milk soft cheese or mixed, ready-to-eat salads
- Hygiene errors: insufficient separation between raw and processed foods
- Lack of personal hygiene in carriers
Growth Conditions
- Temperature: Growth at 8 - 48 °C
- pH value: Growth to min. 4.0
- aw value: Growth to min. 0.95
- Oxygen requirement: facultatively anaerobic
At what temperatures do these microorganisms die?
In general, it can be assumed that these bacteria are killed at a heating temperature of +72 °C for at least two minutes or in an equally effective process. In food, it must be ensured that this temperature-time combination is reached in the core of the product to safely kill the bacteria.
Further Information and Literature
- www.rki.de: under “Infectious Diseases A-Z”
- www.lgl.bayern.de: under „Food“ and then “Hygiene”
- Food Microbiology, J. Krämer and A. Prange, 7th Edition 2017
- Microorganisms in Food, H. Keweloh, 2nd Edition 2008
- Leaflet “Safely Catered – Particularly Sensitive Groups in Community Facilities”, Federal Institute for Risk Assessment, Berlin 2017