E. coli infection

E.coli bacteria

E. coli is a common bug which is present everywhere in the environment.

Mostly it helps people to stay healthy, providing the body with many vitamins, such as vitamin K.

But some strains - such as the O157 strain - are potentially fatal.

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What is E. coli?

E. coli, or Escherichia coli to give it its full name, is a species of bacterium which is found in the intestines of animals and humans.

There are many different types. Some live in the intestine harmlessly, but other can cause a variety of diseases, including cystitis, meningitis and diarrhoea.

The bacterium is found in faeces and can survive in the environment.

It is usually transferred to humans by ingesting contaminated water, or contaminated food, such as meat, which has not been cooked properly.

What is E. coli O157?

A particularly nasty strain of the bacterium, to which children and older people are especially vulnerable.

The strain first appeared in Britain in the 1980s.

It is the most common strain of what is known technically as Vero cytotoxin-producing E. coli (VTEC).

Fewer than 100 of the tiny E. coli organisms can cause illness.

Around 15% of cattle are now thought to carry it in their gut.

The Health Protection Agency recorded 950 cases of illness resulting from E. coli 0157 in England and Wales in 2008.

In the worst recorded outbreak, 20 people died in Scotland in 1996-97 after attending a church lunch in Wishaw, Strathclyde.

Following the Scottish outbreak, the British government set up a commission to look into the issue of food safety.

What are the symptoms?

E. coli O157 symptoms can range from mild diarrhoea to haemorrhagic colitis - a combination of severe abdominal cramps and blood in the stools.

The incubation period can range from three to eight days, with symptoms usually becoming apparent three to four days after infection.

Most people shake off the bug within around a week.

However, a small proportion - up to 7% - of patients also suffer from a complication, haemolytic uremic syndrome (HUS), which kills red blood cells and can cause permanent and severe kidney damage, ultimately requiring dialysis treatment or a transplant.

Children under five are particularly vulnerable to HUS. About 5%-10% of them progress to this stage.

Young children are particularly vulnerable because they cannot tolerate much fluid and blood loss.

The elderly and people with damaged immune systems are also more at risk from the infection.

Symptoms may appear within hours or days, depending on a series of factors, including the number of organisms ingested, the person's state of health and their natural resistance to the bug.

How is it treated?

There is no specific treatment for E. coli O157 infection.

There is no evidence that antibiotics have any positive impact on the O157 strain. In fact their use may increased the risk of HUS.

There is also concern that indiscriminate use of antibiotics will increase the chance that the bug will develop resistance, rendering them less effective as treatments.

Anti-diarrhoeal medication should also be avoided.

It is important to drink plenty of fluids, as diarrhoea can quickly lead to dehydration.

Avoid tea, coffee, fizzy drinks and alcohol, and dilute sugary drinks.

Over-the-counter painkillers such as paracetamol can be used to ease stomach pain, but non-steroidal anti-inflammatory painkillers such as aspirin should not be used as there is some evidence they make kidney problems worse.

If you notice blood in your stools, or watery diarrhoea in children, you should contact your GP immediately.

What can be done to prevent infection?

Good hygienic slaughtering practices in abattoirs reduce contamination of carcasses by faeces.

But it would be wrong to rely on this - it is important to employ good hygiene practice whenever dealing with food.

Raw and cooked meat should be kept apart during food preparation, and people should always wash their hands after handling raw meat.

All meat should be properly and thoroughly cooked - cooking kills the bug.

Beefburgers, for example, should be cooked to a minimum internal temperature of 70C for two minutes.

Other tips from the Health Protection Agency include:

• Ensure that refrigerators are working correctly - bacteria grow more quickly at temperatures over 4C

• Only leave cooked foods, meat and dairy products out at room temperature for a short time

• Store uncooked meats below cooked meats and salad vegetables to avoid dripping juices onto ready to eat food

• Thoroughly wash all salad vegetables that will be eaten raw

In general, keeping your hands clean to avoid faecal contamination is also a good idea.

Try to avoid touching your face with your hands, unless they are clean.

And clean hard surfaces with a disinfectant regularly.