Shiga toxin-producing E. coli (STEC)

Here we explain a bit more about E. coli and STEC, and what you can do to prevent getting ill

Escherichia coli is also known as E. coli, and certain types of it can cause foodborne illness.  It is a bacterium that is commonly found in the gut of humans and warm-blooded animals.  It can be spread by consuming contaminated water or food, or through contact with animals or people who have the infection.

E. coli are a large and diverse group of bacteria. Most strains of E. coli are harmless to humans and they are able to live in the animal gut without causing any problems to their health.  However some strains can cause foodborne illness and are called Shiga toxin-producing E. coli (or STEC for short).  There are many types of STEC that cause disease, the most common being E. coli O157, but there are other types that can cause illness and these are known as non-O157 STEC.  Sometimes STEC will also be referred to as VTEC (Vero cytotoxin-producing E. coli) but it is the same bacteria.

STEC is an important public health challenge in Scotland, as it continues to cause outbreaks of infection, severe illness and, in some cases, death, particularly amongst the very young.  With approximately 150-200 cases of E. coli O157 each year (and approximately 50 non-O157 STEC), Scotland consistently reports higher rates of infection compared to other UK countries.  The highest rate of infection is reported in those under 16 or over 60 years of age.

What happens if you get infected by STEC

Infection with STEC, usually results in symptoms appearing three to four days later and these symptoms include:

  • abdominal cramps
  • watery and/or bloody diarrhoea,
  • fever
  • vomiting

Some people infected with STEC may go on to develop more severe complications, such as haemolytic-uraemic syndrome (HUS).  HUS can lead to kidney failure and the risk of HUS is highest in children aged under five years.  STEC infection is more likely to occur in vulnerable groups such as those young in age, the elderly and those with a weakened immune system.

To find out more information on what to do if you think you have STEC infection go to NHS Inform.

Preventing STEC food poisoning

STEC infection can occur by eating contaminated food and touching infected animals or coming into contact with their faeces.  You can also become infected through contact with people who have the illness, particularly if you do not wash your hands thoroughly after using the toilet. Remember hands do not need to look dirty to have bacteria on them.

In the kitchen, STEC can spread by improper handling and cooking of food.  This can happen by eating contaminated food such as undercooked meat, dairy products made from unpasteurised milk or raw vegetables and salad.  STEC can also spread by eating other food items that have become cross-contaminated by poor food hygiene after handling raw meat or other contaminated foods.

You can see how to keep your food and kitchen safe by following the 4Cs

Under the microscope - How STEC makes you ill

STEC causes disease by producing toxins in the intestine of the person with E. coli food poisoning. Once ingested, the bacteria rapidly multiply in the intestine and bind to the intestine wall. It is only when the bacteria has attached to the cell wall that the toxin is absorbed into the body, making people ill. The toxins cause inflammation, cell walls to rupture and destroy red blood cells.

Once the toxin reaches a target organ it can bind to the cells that make up the organ.  Doing this means that the toxin can get inside the cell.  Once the toxin is inside the cell it stops it from working properly.  When the cell is not able to function properly it will die.  This means that the cells crucial for the function of the organ are dying so the organ can’t operate as it should.  Which in turn leads to the toxins having a debilitating effect on the human body.

Our research

Our research has covered a wide range of STEC issues including risks associated with fresh produce, sprouted seeds, sheep, cattle and venison. Below are a few examples of work that FSS has been involved with:

The research on fresh produce has included work to look at the risks and the potential spread of STEC to carrots, potatoes and leeks to assess the risk to human health of contaminated produce being sold.  We have also funded work to understand the potential of bacteria being able to live inside salad plants. Due to an E. coli outbreak in Europe in 2011, a piece of research was undertaken to assess different treatments home sprouters could use to decontaminate seeds for sprouting.

Recently published research investigated E. coli in cattle and showed that the overall prevalence of E. coli O157 in cattle is similar across Great Britain, and has remained relatively consistent in Scotland over the last decade.  However, there are a greater diversity of E. coli O157 types circulating in England and Wales compared to Scotland, but Scotland has a high level of a certain type of E. coli O157 that is associated with severe human infection.  The study also undertook initial experiments to test a vaccine, which was found to limit both excretion from cattle as well as transmission to other cattle and could have an impact in the future in reducing human exposure and infection from E. coli O157. 

FSS is currently undertaking research to understand the prevelance (i.e. numbers) of pathogens through a retail mince survey which involves collecting data on the microbiological quality of retail beef mince on sale in Scotland.

Following an E. coli outbreak in 2015 associated with the consumption of venison products FSS commissioned a project to understand the risks of contamination of wild venison meat.

FSS was part of a Scottish Government multi-agency working group to address the 86 recommendations of the VTEC Action Plan for Scotland. The final report detailing how recommendations have been addressed was submitted to Scottish Government in December 2018. A new Scottish Health Protection Network (SHPN) working group, which FSS is co-chairing, has been established to monitor the impact of interventions for reducing risks of STEC and to assess the need for further action.

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