Bloomberg News

Sprouts Can’t Be Excluded as E. Coli Source, Researchers Say

June 07, 2011

(Updates number of deaths in first, sixth paragraphs.)

June 7 (Bloomberg) -- Sprouts can’t be ruled out as a cause of the German E. coli outbreak that killed 23 people because the bacterium may have gone from the farm where they were grown, scientists said.

Initial tests from an organic farm in northern Germany showed no evidence of the bacteria, authorities in Lower Saxony state said yesterday. Traces may be undetectable now if the offending produce was grown from a depleted batch of contaminated seed weeks ago, said James Paton, head of the bacterial pathogenesis laboratory at the University of Adelaide in South Australia.

More than a dozen samples from the farm, near Uelzen, are still being checked, and the cause of the month-old epidemic remains unknown, according to health officials in Hamburg, which the European Union said is the “epicenter” of illnesses. Seventeen cases were tied to a restaurant in Luebeck, about 65 kilometers (40 miles) away, which got supplies from Hamburg.

“They are still pretty strongly suspicious of the sprouts because the epidemiological link was strong,” Paton said in a telephone interview today. “It’s just that they haven’t found it at the farm.”

The property, Gaertnerhof Bienenbuettel, which has produced sprouts for 25 years, said it recalled produce and informed its customers immediately. Lab tests in mid-May found no evidence of E. coli, its proprietors said in a statement, adding they were “shocked and concerned” at being linked to the infection.

Women Patients

The German O104 E. coli strain produces a toxin that attacks the kidneys and blood vessels. Since May 2, 674 people have developed the life-threatening complication in the EU, and an additional 1,755 have been stricken with diarrhea, the European Centre for Disease Prevention and Control said today. A total of 23 people have died, according to the ECDC.

While the number of new cases of E. coli infection is rising at a slower rate, it’s too early to “give the all- clear,” said Cornelia Pruefer-Storcks, the health senator for the city of Hamburg, at a press briefing today. She said the exact cause of the outbreak may never be known.

Most cases have occurred in adult women and those who recently traveled to the north of Germany -- mainly Schleswig- Holstein, Lower Saxony, North-Rhine-Westphalia and Hamburg, the Stockholm-based European health agency said.

“It’s not normal that people go out for a salad and die of the consequences,” Linda McAvan, a U.K. member of the European Parliament, said today at a session devoted to the outbreak.

Kidney Damage

The epidemic has killed more people and resulted in more cases of severe kidney damage than any outbreak on record. About 9,451 people were sickened and 12 killed in a series of outbreaks in Japan between May and December 1996, according to a 1999 study in the American Journal of Epidemiology. The majority of those cases were acquired by tainted radish sprouts in school lunches.

Radish seeds experimentally infected with the germ produced contaminated sprouts, suggesting the original source may not be the farm supplying the produce, researchers in Tokyo reported in a 1998 study.

“All of their water systems may be perfectly okay and their production methods may be fine, it’s just that they are starting off with contaminated seed stock,” said Paton, who was among the first scientists to use DNA analysis to trace food- borne outbreaks in Australia in the early 1990s. “If you just had a single-batch contamination, then the likelihood of there being any traces left over are remote.”

Hard to Find

Evidence in restaurants and households may also be hard to find as any offending sprouts would likely have perished in the weeks since cases were first reported, he said.

It’s possible the source of the German outbreak may never be discovered, said Robert Hall, a senior research fellow at Monash University’s School of Public Health and Preventive Medicine in Melbourne, Australia.

“It gets really tough at this stage, and I suspect they may not get it out,” said Hall, who investigated numerous outbreaks of food-borne diseases as the former director of communicable disease control with the South Australian health department in Adelaide.

“You have got to make a lot of fine judgments and you’ve got to do them in a tearing rush, and with the eyes of the world’s media glaring at you,” Hall said in a telephone interview today.

Food Targets

Most disease investigators use methods based on those described by Michael Gregg, an epidemiologist with the U.S. Centers for Disease Control and Prevention who edited the textbook Field Epidemiology in 1996, Hall said.

The process typically involves interviewing dozens of people who fell ill to screen for potential risk factors, including commonly consumed food and beverage items, he said. The same questions are then posed to about three times as many unaffected people, or “controls,” and the data compared in order to discern key differences.

“That’s quite a difficult thing to do, especially if you’re doing it in a big rush, which you always are,” Hall said. “On the basis of the differences, you can get an epidemiological association, which if you’re lucky, you can then use to identify the food and test the food. And if you’re really lucky, it turns out positive as well.”

Once food targets have been identified, investigators will usually also look for possible contaminants in the environment, Hall said.

“Part of the difficulty is that it might be quite widespread through all kinds of cross-contamination mechanisms, or it might just be a single producer,” he said. “If it’s a single producer, then that’s usually quite easy to control once you’ve found it. Then the court cases begin.”

‘A Great Failure’

EU agriculture ministers are meeting in Luxembourg today. Vegetable supplies are being destroyed and prices for cucumbers, lettuce and tomatoes are tumbling after demand slumped and Russia banned imports. Farmers are losing millions of euros a day and some are being forced out of business by the crisis, according to Copa-Cogeca, a farm lobby group based in Brussels.

“There has been a failure, there has been a great failure, and we have to take that into account and try to improve our safety system so that it will never happen again,” French Agriculture Minister Bruno Le Maire said in an interview in London today.

European Health Commissioner John Dalli, speaking at the same session of the European Parliament as McAvan, emphasized the need to “reduce unnecessary fears” by communicating facts that are based on science rather than speculation.

“It is crucial that national authorities do not rush to give information on a source of infection that is not” backed by science analysis, Dalli said. “We must be careful not to make premature conclusions.”

--With assistance from Allison Connolly in Frankfurt, Niklas Magnusson in Hamburg, Naomi Kresge in Berlin, Stuart Wallace in London and Marthe Fourcade in Paris. Editors: Kristen Hallam, Marthe Fourcade.

To contact the reporter on this story: Jason Gale in Singapore at

To contact the editor responsible for this story: Jason Gale at

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