E.coli O157 and Food Safety

You may have heard of the bug E.coli O157 but do you know why it is such a significant organism in relation to food safety? It has been implicated in a number of high profile food poisoning outbreaks involving the deaths of it’s victims; particularly vulnerable people such as the very young or elderly.

The incubation period (that is, the period it takes from consumption until the time you exhibit symptoms) can, typically be any time between one and 6 days (in some cases as long as two weeks). Not everyone exhibits serious symptoms though. Symptoms range from mild diarrhoea, fever and stomach cramps, to kidney failure and death.

E.coli is characterised by it’s low infective dose as it is possible to be infected by just a few bacteria. Other pathogens typically require hundreds or thousands of bacteria to be consumed in order to infect the consumer. For this reason it can also be transferred very easily from person to person via faecal-oral route; particularly in child-care situations.

Where does E.coli O157 it come from?

Coliforms are bacteria that are held in the gut of animals and humans. As a result, anything contaminated in faecal matter is likely to also be contaminated with coliforms. E.coli O157 is associated with farm animals, particularly, cattle. As farm animals don’t tend to be the cleanest of creatures they are likely to be contaminated with faecal matter; and there is a good chance that very small amounts of this can contaminate meat during the slaughter process.

They can also result in contamination of soil, water and dairy products. Hence water supplies have also been implicated in some outbreaks as have vegetables that have become contaminated on the farm.

Control of E.coli O157 and food safety

Controls at primary production are important; if levels of pathogens can be reduced on the farm they are less likely to be transferred to our plate. Similarly, good hygiene at the slaughter house and cutting plants will also reduce spread and further contamination. However, it is not possible to rely upon these controls and measures must be taken by manufacturers and caterers to prevent survival of E.coli O157 and any further spread by cross-contamination.

As infection is caused by consuming contaminated food or drink it is important that food be cooked thoroughly wherever possible. Any minced meat products or rolled joints must be cooked thoroughly to destroy the bacteria (including burgers). Whole cuts of read meat such as steaks or joints may be served ‘rare’ as long as the entire outer surface of the meat is cooked thoroughly. Special preparation methods (such as ‘sear and shave’ may be used in the case of steak tartare, carpaccio or other similar products).

Salads may be washed thoroughly before use; and any vegetables contaminated with soil must be peeled and rinsed where appropriate. Always avoid washing ready to eat foods such as salads in equipment that may have come into contact with raw foods.

Raw, unpasteurised, milk is a no-no. Unpasteurised dairy products and cheeses that have been processed appropriately carry a lower risk but should still be avoided (particularly if you are vulnerable or unwell).

Thorough hand washing and the prevention of cross-contamination are important; as is suitable chemical and thermal disinfection for equipment and exposed surfaces.

Usually, anyone working in a food establishment who has experienced mild gastroenteritis must not come back to work until 48 hours have expired since the last symptoms. However, it is important that workers who are known to be, or suspected to be close contacts of anyone suffering from, E.coli O157 are screened before returning to work.