A strain of E. coli spreading across Europe is a previously unseen variant of the bacterium, and one that is more virulent than seen before, health officials say.

Scientists also said the new strain appeared likely to be resistant to common antibiotics.

By June 2, 18 people had died and more than 2,000 had become infected from eating contaminated vegetables. The bacterial outbreak had spread beyond Germany to 10 countries.

After scientists sequenced the genetic code of the E. coli, Hilde Kruse, a food safety expert at the World Health Organisation (WHO) told Associated Press: “This is a unique strain that has never been isolated from patients before ... [there are] various characteristics that make it more virulent and toxin producing.” A spokesperson for the U.K.'s Health Protection Agency said scientists at the organisation had not sequenced the bacterium but had agreed with the WHO finding that the E. coli O104 strain associated with the outbreak “which we know to have a highly unusual combination of virulent properties, could be one that has never been seen before.”

Stephen Smith, a clinical microbiologist at Trinity College, Dublin, said the new E. coli strain was a “mongrel” combining two “nasty” types of the bacterium. He said: “It is very similar to enteroaggregative E coli which has been associated with outbreaks of watery diarrhoea, in developing nations since 1970. However, this bacterium has been recognised as a cause of diarrhoea in industrialised nations and has caused outbreaks in the U.S., Sweden, Britain and Germany.”

The toxin produced by the bacterium binds to, and damages, kidney cells and leads to haemolytic uraemic syndrome (HUS), a rare and severe complication that destroys red blood cells and can affect the central nervous system. More than 500 cases of HUS have been reported in Germany and three cases were found in the U.K. in people who had recently been to Germany.

An HPA spokesperson said: “Bacteria and viruses are evolving all the time. We expect to see new strains, sometimes more virulent or resistant to antibiotics than others, and plan on that basis.”

What is E. coli? Escherichia coli is a bacterium found in the intestines of many animals, including humans and many types of the bug are relatively harmless. Some strains, however, can cause illness in people, including diarrhoea that usually settles within a week without the need for treatment.

How does it spread? Both harmless and disease-causing strains of E. coli get into humans through contaminated food or water. The vegetables that are contaminated in Germany might have been fed with water containing the bacterium or there might have been faecal material in the soil in which they were grown.

Why is the German strain so dangerous? The E.coli that cause human disease are often classified by the type of disease that they cause or the toxins they can produce. The most serious are referred to as “verocytotoxin-producing”. The Health Protection Agency said that the German strain is the rare E. coli (VTEC) O104 version. It has led to some cases of a serious kidney and blood complication called haemolytic-uraemic syndrome (HUS).

What is haemolytic-uraemic syndrome? This is a disorder that usually occurs when an infection, usually E. coli, in the digestive system produces toxic substances that can get into the blood stream and cause kidney disease. It is most common in children and the elderly. Symptoms include diarrhoea first, which may contain blood. It is a serious condition but around 98 per cent of people recover.

How can the spread be stopped? Health protection professionals recommend washing hands regularly to prevent person-to-person spread of the bacterium.

Washing vegetables before consumption will also help to remove bacteria from the surface, as will peeling or cooking. Anthony C. Hilton a microbiologist at Aston University, England, said that if the current strain is a novel virulent type “it will be important to determine if this is simply surface contamination of vegetables or if the organism has developed a mechanism of intracellular invasion and persistence, as that will greatly influence the effectiveness of the simple washing of vegetables intended to be eaten raw as a means of reducing the risk of infection.” — © Guardian Newspapers Limited, 2011

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