Tuesday, 31 May 2011

BBC News - Q&A: Contaminated vegetables

31 May 2011 Last updated at 13:54

Share this page

Q&A: Contaminated vegetables

By Helen Briggs Health editor, BBC News website
E coli The bacteria produces a toxin that can be fatal

An outbreak of E. coli in Germany linked to contaminated imported vegetables, has caused at least 14 deaths and hundreds of infections.

What is E coli?

E. coli is short for Escherichia coli. It is a type of bacteria present in the gut of humans and other animals. Most strains are harmless but some are able to produce a toxin that can cause symptoms such as severe cramps and diarrhoea.

What do we know about this outbreak?

The outbreak in Germany is causing severe infections, affecting the blood, kidneys and sometimes the central nervous system.

The condition - haemolytic uraemic syndrome - is an unusual complication of some types of E. coli as well as other infections.

Symptoms include bloody diarrhoea, kidney failure and epileptic fits.

The strain suspected is O104, which is rare.

Another serious strain - known as O157 - causes similar symptoms, and has been associated with E. coli outbreaks from the 1980s onward.

Where has it come from?

The source of this outbreak is believed to be contaminated vegetables.

German officials claim some organic cucumbers imported from Spain have been found to be carrying the bacteria but said on Tuesday that it may be from a different strain.

While E. coli infection is often caused by eating undercooked meat and eggs, there has been a recent rise in cases linked with fresh fruit and vegetables.

They include foods that are eaten raw or only lightly cooked, such as salads, fresh fruit and bean sprouts.

What can you do?

German authorities have warned people to avoid eating raw cucumbers, tomatoes and lettuce.

The Food Standards Agency says there is no evidence that any affected cucumbers have been imported into the UK.

But it has issued general advice to wash fruit and vegetables.

The agency said: "It's a good idea to wash fruit and vegetables before you eat them to ensure that they are clean, and to help remove germs that might be on the outside.

"Peeling or cooking fruit and vegetables can also remove these germs."

However, a Scottish expert said new research suggests washing alone may not be enough, as the bacteria may be inside the food.

Dr Nicola Holden of The James Hutton Institute said: "The bacteria are able to get from animal sources on to crops through different routes, most likely in irrigation water or sometimes from slurry spraying, while some contamination can also occur during processing and packaging."

She said the bacteria can colonise plant roots, moving up to the edible foliage or fruits.

"The threat to human health occurs because these bacteria are not simply sitting on the surface of the plant and are particularly difficult to remove post-harvest," she added.

What do other experts say?

Professor Brendan Wren from the London School of Hygiene & Tropical Medicine said E. coli can attach to the surface of fresh produce such as lettuce leaves, spinach leaves and cucumber.

"These type of E.coli survive harsher environmental conditions than the typical E. coli and produce some nasty toxins to humans," he said.

"They can survive in soil environments and fertiliser may be one source for the origin of the outbreak related to fresh produce such as cucumbers."

Dr Jonathan Fletcher, senior lecturer in microbiology at the University of Bradford, said toxin-producing E. coli can cause very serious disease in humans, especially in the elderly or very young.

Cattle seem to carry the toxin in their gut, he added, without showing signs of illness, and it will be shed in the faeces.

"If cattle manure is used as a fertiliser, it is probable that vegetables such as cucumbers will be contaminated with E. coli, and if not washed properly it would be present in sufficient numbers to cause the infection."