E coli

E coli or to be precise, the E coli 0157:H7 strain of bacteria has been responsible for some of the worst outbreaks of food poisoning over the last decade or so.

E coli or ‘Escherichia coli’ is a bacterium, shaped like a rod which is usually found within the lower intestine of warm blooded animals. However this strain of bacteria is able to live for relatively short periods of time outside of the body. This enables it to be detected within food and water.

There are several strains of E coli bacteria which reside within the lower intestine and perform a range of useful functions, such as protecting the body against disease and infection.

But the E coli 0157:H7 strain is harmful to its environment (e.g. gastrointestinal tract in humans), resulting in food poisoning and in some cases, life threatening illnesses.

The E coli 0157:H7 strain of bacteria

This is a pathogenic strain of bacteria which means that it has the qualities of a germ or infectious agent. This type of bacteria is able to cause disease, such as food poisoning, within its ‘host’.

Note: The term ‘host’ means the animal or person the bacteria are living in.

This bacterial strain contains extra genes which are a code for the production of toxins and associated proteins. This is what transforms a friendly strain of bacteria into a harmful strain.

This type of E coli produces toxins which cause a type of food poisoning known as ‘enterohaemorrhagic’: this means that it is causes infection and bleeding (haemorrhagic) within the intestinal (entero) system.

There are two other strains of E coli which also cause food poisoning. These are the 0121 and 0104:H21 strains which are also pathogenic although less common than the 0157:H7 strain.

The 0157:H7 strain produces a toxin – known as the Shiga toxin, which attacks the cells within the intestine causing bleeding and a serious infection. In a few cases this leads to complications such as kidney damage.

Foods which contain the E coli bacteria

The E coli 0157:H7 strain can normally be found in raw or undercooked meat, especially beef, unwashed vegetables, unpasteurised milk and milk which has become infected following pasteurisation.

Causes of E coli poisoning

The 0157:H7 bacteria is transmitted into the human body as a result of eating undercooked meat, e.g. minced beef or, personal contact with another infected person or animal, or touching soil which has become infected with contaminated animal faeces.

Unfortunately, it only requires a small number of E coli bacteria to cause food poisoning.

Symptoms of E coli poisoning

Once these bacteria have invaded the digestive system they reproduce very quickly within the large intestine. They attack the cells within the lining of the intestine causing the following symptoms:

• Abdominal pain
• Watery diarrhoea
• Nausea

This diarrhoea is usually severe and may contain blood, especially after the first day.

Vomiting is likely but tends to be very rare. Diarrhoea is the main symptom which can last for a week or even longer.

Treatment for E coli poisoning

Replacement fluids are the most important aspect of any treatment. This involves drinking fluids which contain electrolytes in order to top up low levels of vitamins and minerals, for example sodium and potassium.

These fluids can be given intravenously in severe cases.

The person affected will need to get plenty of rest and support from people close by to him/her.

This type of food poisoning is caused by bacteria so antibiotics may be prescribed although the problem with this is that they may increase the risk of complications. Plus there is also the fact that some strains of bacteria have become resistant to the effects of antibiotics. This can be attributed to over-prescribing antibiotics when it is not always necessary to do so.

Complications of E coli poisoning

The main complication is ‘haemolytic uraemic syndrome’. This occurs when toxins from the E coli bacteria damage the delicate tissues of the kidneys. These toxins also destroy red blood cells which results in a low platelet count and anaemia.

Haemolytic uraemic syndrome is discussed separately in our complications of food poisoning section.

Another problem which is also related to broken down red blood cells, and a low platelet count is ‘thrombotic thromcytopaenic purpura’. This causes blood clots to form within blood vessels which affect normal circulation, damage to internal organs and a tendency to bleed into the skin (purpura).

This disease is more likely to affect the elderly.

Neurological problems are another complication.

Prevention of E coli poisoning

Many people consider this to be worst form of food poisoning so with this in mind; it is a good idea to take a few precautions against the risk of contracting this nasty illness.

These include:

• Checking that any meat, particularly beef, has been cooked properly. Use a meat thermometer to check for a safe temperature: but failing that, poke a skewer into the middle of a joint of meat and if the juices run clear then consider it to be cooked.
• Keep raw and cooked meat away from each other. Store them on separate shelves within the fridge but do not allow blood to drip from raw meat onto cooked meat.
• Wash your hands before and more importantly, after you have handled raw meat.
• Drink pasteurised milk only.

These should help to reduce the risk of e coli poisoning.