Recently consumers in 12 countries including Germany, other European and even North American regions are concerned by an outbreak of enterohemorrhagic Escherichia coli (EHEC). By June 6, 2011, Authorities have registered 22 fatalities and ca. 2000 infections connected to EHEC1 with steadily increasing numbers. Female consumers have shown to be especially vulnerable to the infection. Various possible sources of the pathogen are currently under discussion. There is a high likeliness that the source of the bacteria is connected to contaminated food products.
The root cause of the EHEC outbreak is the bacteria Escherichia coli O104:H4. It is a rare enterohemorrhagic strain of the bacterium Escherichia coli and produces cytotoxins or so called Shiga-like toxins. Shiga toxigenic Escherichia coli (STEC) are conventionally defined as E. coli which contains one or both of the genes (stx1or stx2) responsible for the production of this specific group of cytotoxins. Based on this definition, there are between 100-250 different serotypes of STEC. However, not all serotypes are considered pathogenic.
EHEC can grow in temperatures ranging from 7°C to 50°C, with an optimum temperature of 37°C. Some EHEC can grow in acidic foods, down to a pH of 4.4, and in foods with a minimum water activity (Aw) of 0.95. Escherichia coli O157:H7 is the most important EHEC serotype in relation to public health; however, other serotypes have frequently been involved in sporadic cases and outbreaks.
The recent bacteria strain is multi resistant to antibiotics because of the production of the ESBL CTX-M enzyme (Group 1). This characteristic together with the screening of the stx1 and stx2 genes can lead to the isolation and identification of STEC. Further DNA analyses can identify E. coli O104:H4.
Only a small amount of these bacteria may be sufficient to cause illness and immediate medical treatment may necessary. Nonetheless infected humans may develop a severe illness called hemolytic-uremic syndrome (HUS). In the course of this infection bacteria toxin will destroy blood cells which may lead to kidney failure.
The German Institute of Risk Assessment (BfR) assumes that the outbreak is connected to certain foodstuff2 but also direct infection from animals to humans is possible3. Washing and peeling of vegetables reduces the microorganism count and hence the risk of infection. However, they do not completely eliminate EHEC. BfR recommends applying good food hygiene practices to avoid infection.
Good practice will include:
- Washing hands thoroughly before and after preparing food
- Separate food preparation of raw meat and vegetables (incl. storage devices and any kind of kitchen helpers)
- Clean all surfaces in food contact with rinsing agent and hot water after contact with raw meat, its packaging or condensation water
- Replace washcloth and towels frequently after preparation of raw meat and wash them at minimum 60°C
- Vegetables, fruits and other foods which may have been in contact with suspected contaminated products should not be consumed raw
- Crude fruit and vegetables should be washed long and thoroughly prior to consumption with hot water and strong rubbing. Peeling is recommended
Cooking, frying and stewing will kill EHEC if the whole food will be heated to a temperature of 70 °C and the heat will be maintained for at least two minutes. Other food treatment or environmental conditions such as freezing, acidity or desiccation is not a reliable means to kill the bacteria since the bacteria is comparatively insensitive to such influences.
Despite good hygiene practices, the best way to avoid infection of consumers is to prevent contaminated products reaching the grocery shelves.
SGS as the world’s leader in third party testing has established test procedures to determine the bacteria Escherichia coli O104:H4. Providing service to the whole food supply chain from farm to fork will help to assure your products are fit for the market.
1 Preliminary E. coli tests on sprouts prove negative
2 Enterohemorrhagic Escherichia Coli (EHEC) Outbreak In Germany (PDF 314 KB)
3 New epidemiological data corroborate existing recommendation on consumption by BfR.
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