New E. Coli strain: Combination of two different E. Coli bacteria

Genetic sequencing suggests it is more virulent and toxin-producing

By Maria Cheng
AP
June 2, 2011

An entirely new super-toxic bug is causing the frightening food poisoning outbreak that has sickened at least 1,600 people and killed 18, researchers and global health officials said Thursday.

The DNA of the new E. coli strain, believed to have contaminated salad vegetables, was analyzed by Chinese and German scientists. It contains several genes that cause antibiotic resistance and is similar to a strain that causes serious diarrhea and is found in the Central African Republic, according to a statement from the Shenzhen, China-based laboratory, BGI. Those scientists were working together with the University Medical Center Hamburg-Eppendorf.

“This is a unique strain that has never been isolated from patients before,” Hilde Kruse, a food safety expert at the World Health Organization, told The Associated Press. The new strain has “various characteristics that make it more virulent and toxin-producing” than the many E. coli strains people naturally carry in their intestines.

Preliminary genetic sequencing suggests the strain is a never before seen combination of two different E. coli bacteria, with aggressive genes that could explain why the outbreak appears to be so massive and dangerous, the agency said.

Researchers have so far been unable to pinpoint the food source of the illness, which has now spread to at least 10 European countries and fanned uncertainty about eating tomatoes, cucumbers and lettuce. The germ has caused 499 to develop a kidney failure complication. Germany is hardest hit.

Fearful of the outbreak spreading east to Russia, the country extended a ban on vegetables to the entire European Union from just Germany and Spain, a move the bloc quickly called disproportionate.

Kruse said it’s not uncommon for bacteria to continually mutate, evolving and swapping genes. It is difficult to explain where the new strain came from, she said, but strains of bacteria from both humans and animals easily trade genes, similar to how animal viruses like Ebola sometimes jump into humans.

“One should think of an animal source,” Kruse said. “Many animals are hosts of various types of toxin-producing E. coli.” Some scientists suspect the deadly E. coli might have originated in contaminated manure used to fertilize vegetables.

Previous E. coli outbreaks have mainly hit children and the elderly, but the European outbreak is disproportionately affecting adults, especially women. Kruse said there might be something particular about the bacteria strain that makes it more dangerous for adults.

But she cautioned that since people with milder cases probably aren’t seeking medical help, officials don’t know just how big the outbreak is. “It’s hard to say how virulent (this new E. coli strain) is because we just don’t know the real number of people affected.”

Nearly all the sick people either live in Germany or recently traveled there. British officials announced four new cases, including three Britons who recently visited Germany and a German person on holiday in England.

The WHO recommends that to avoid food-borne illnesses people wash their hands before eating or cooking food, separating raw and cooked meat from other foods, thoroughly cooking food, and washing fruits and vegetables, especially if eaten raw. Experts also recommend peeling raw fruits and vegetables if possible.

Russia had earlier this week banned fresh imports from Spain and Germany, but it expanded the ban Thursday to include the entire EU. The United Arab Emirates issued a temporary ban on cucumbers from Spain, Germany, Denmark and the Netherlands.

Lyubov Voropayeva, spokeswoman for the Russian Agency for the Supervision of Consumer Rights, told the AP the Russian ban has been imposed immediately and indefinitely. No fatalities or infections have yet been reported in Russia.

“How many more lives of European citizens does it take for European officials to tackle this problem?” the agency’s chief Gennady Onishchenko said to the state-owned RIA Novosti news agency.

Frederic Vincent, a spokesman for the EU’s Health and Consumer Policy Commissioner John Dalli, said Thursday that the European Commission would write to Russia to demand further clarification. The Italian farmers association Coldiretti criticized the ban as “absurd.”

One expert said the fact the strain is new may have complicated the response to the outbreak. “Officials may not have had the correct tests to detect it, which may explain the initial delay in reporting,” said Paul Hunter, a professor of health protection at the University of East Anglia in England.

He said the number of new cases would likely slow to a trickle in the next few days. The incubation period for this type of E. coli is about three to eight days, and most people recover within 10 days.

“Salads have a relatively short shelf life and it’s likely the contaminated food would have been consumed in one to two weeks,” Hunter said.

But Hunter warned the outbreak could continue if there is secondary transmission of the disease, which often happens when children are infected. The disease can be spread when infected people don’t take proper hygiene measures, like bathing or hand washing..

Phil Tarr, a professor of molecular microbiology at Washington University, said the discovery of a new strain wasn’t particularly significant scientifically.

“Every strain is a mutant, if you define mutant as an organism that has picked up DNA from another source,” he said. He said more analysis was needed to find out more about the strain’s origins, how long it’s been around and its ability to make people sick.

Meanwhile, Spain’s prime minister slammed the European Commission and Germany for early on singling out the country’s produce as a possible source of the outbreak, and said the government would demand explanations and reparations.

Jose Luis Rodriguez Zapatero told Spanish National Radio that the German federal government was ultimately responsible for the allegations, adding that Spain would seek “conclusive explanations and sufficient reparations.”

Spanish farmers say the accusations have devastated their credibility and exports. In Valencia, protesting farmers dumped some 300 kilos (700 pounds) of fruit and vegetables — cabbage, tomatoes, peppers, cucumbers and other produce — outside the German consulate.

The outbreak is already considered the third-largest involving E. coli in recent world history, and it may be the deadliest. Twelve people died in a 1996 Japanese outbreak that reportedly sickened more than 9,000, and seven died in a 2000 Canadian outbreak.

European food poisoning mystery deepens

By David Rising and Maria Cheng
Associated Press
June 1, 2011

The number of people hit by a massive European outbreak of foodborne bacterial infections is a third bigger than previously known and a stunningly high number of patients suffer from a potentially deadly complication than can shut down their kidneys, officials said Wednesday.

The death toll rose to 17, with German authorities reporting that an 84-year-old woman with the complication had died on Sunday.

Medical authorities appeared no closer to discovering either the source of the infection or the mystery at the heart of the outbreak: why the unusual strain of the E. coli bacteria appears to be causing so many cases of hemolytic uremic syndrome, which attacks the kidneys and can cause seizures, strokes and comas.

Germany’s national health agency said 1534 people in the country had been infected by enterohaemorrhagic E.coli, or EHEC, a particularly deadly strain of the common bacteria found in the digestive systems of cows, humans and other mammals. The Robert Koch Institute had reported 1169 a day earlier.

The outbreak has hit at least eight European countries but virtually all of the sick people either live in Germany or recently traveled there.

The Robert Koch Institute said 470 people in Germany were suffering from hemolytic uremic syndrome, or HUS, a number that independent experts called unprecedented in modern medical history. HUS normally occurs in 10 percent of EHEC infections, meaning the number seen in Germany could be expected in an outbreak three times the size being currently reported.

That discrepancy could indicate that a vast number of cases haven’t been reported because their symptoms are relatively mild, medical experts said.

But they also offered another, more disturbing theory – the strain of EHEC causing the outbreak in Europe could be more dangerous than any previously seen.

“There may well be a great number of asymptomatic cases out there that we’re missing. This could be a much bigger outbreak than we realize right now,” said Paul Hunter, a professor of health protection at the University of East Anglia in England. “There might also be something genetically different about this particular strain of E. coli that makes it more virulent.”

There are hundreds of different E. coli strains in the environment – every person naturally carries the bacteria – but only a very small percentage are dangerous. EHEC is not normally in the environment, but improper use of manure can contaminate fresh produce.

German Agriculture Minister Ilse Aigner said scientists were working nonstop to find the source of the EHEC that is believed to have been spread in Europe on tainted vegetables – and where in the long journey from farm to grocery store the contamination occurred.

“Hundreds of tests have been done and the responsible agencies … have determined that most of the patients who have been sickened ate cucumbers, tomatoes and leaf lettuce and primarily in northern Germany,” Aigner said on ARD television. “The states that have conducted the tests must now follow back the delivery path to see how the cucumbers, or tomatoes or lettuce got here.”

German authorities initially pointed to cucumbers from Spain after people in Hamburg fell ill after eating fresh produce. After tests of some 250 samples of vegetables from around the city, only the three cucumbers from Spain and one other of unknown origin tested positive for enterohaemorrhagic E.coli, or EHEC.

But further tests showed that those vegetables, while contaminated, did not cause the outbreak. Officials are still warning all Germans to avoid eating raw cucumbers, tomatoes or lettuce.

Some experts said it might be impossible to ever identify what caused the outbreak, as much of the tainted fresh produce may already have disappeared from markets.

“As in many foodborne disease outbreaks, the culprit may never be identified and the epidemic just fades away,” said Brendan Wren, professor of pathogen molecular biology at the London School of Hygiene and Tropical Medicine.

To identify which E. coli strain is responsible, scientists must grow the suspect bacteria in a laboratory, which can take up to two days. Once that’s done, tests to characterize the strain may take another day or two and those tests can only be done in specialized labs.

“These are complicated molecular tests and it’s not something you can do in one day,” Hunter said.

Spanish officials said, meantime, that they were considering legal action after Europeans swore off Spanish produce in droves after the initial report. And in Germany, farmers’ association president Gerd Sonnleitner said the call for people to avoid raw vegetables had cost local farmers an estimated euro30 million ($43 million) so far.

Germany typically sees a maximum of 50 to 60 annual cases of HUS, which has up to a 5 percent fatality rate according to the World Health Organization.

More than 60 percent of the EHEC cases in Germany have been women – 88 percent over the age of 20 – and nearly 90 percent of the HUS cases have been women over the age of 20.

Experts suspect the outbreak may be mainly striking women because they are the ones most likely to be eating fresh produce. “We should be open to whatever the investigation shows, but adult women are more likely to be exposed to vegetables than other populations,” said Hilde Kruse, a food safety expert at the World Health Organization.

Last week, Reinhard Burger, head of the Robert Koch Institute, said it was also possible more women were affected because they were predominantly the ones handling food in the kitchen.

The World Health Organization said cases of EHEC have been reported in nine European countries: Austria, Denmark, Germany, the Netherlands, Norway, Spain, Sweden, Switzerland and the U.K. All but two cases are either people in Germany, or people who had recently traveled to northern Germany, the organization said.

In addition, Sweden has reported 15 cases of HUS, followed by Denmark with 7, the Netherlands with 3, the U.K. with 2 and Spain with 1, according to the European Center for Disease Prevention and Control.

It’s “extraordinary” to see so many cases of the kidney complication from a foodborne illness, said Dr. Robert Tauxe, a foodborne disease expert at the U.S. Centers for Disease Control and Prevention. “There has not been such an outbreak before that we know of in the history of public health.”

He added that the strain of E. coli in the European outbreak has not been seen in the United States, where there have been several high-profile foodborne outbreaks in recent years, but none with such a high death toll.

There’s little precedent in Europe, either. In 1996, an E. coli outbreak in the United Kingdom caused 216 cases and 11 deaths.

The World Health Organization said 86 percent of those sickened in the current outbreak were adults, and two-thirds were women. It said it was unusual that more children weren’t affected.