French tests suggest E coli matches German outbreak strain

Jun 30, 2011 (CIDRAP News) – A French probe into a cluster of Escherichia coli O104:H4 infections in Bordeaux revealed today that the strain isolated from patients is genetically related to the one that has sickened thousands of people in Germany, according to a Eurosurveillance report.

The report also includes new details about the epidemiologic investigation that pointed to sprouts, adding further evidence that a common source is responsible for both outbreaks. European investigators said yesterday they are exploring the possibility that contaminated lots of Egyptian fenugreek seeds could be linked to both outbreaks.

Public health officials received a report on Jun 22 of eight cases of bloody diarrhea, six involving hemolytic uremic syndrome (HUS). The initial epidemiologic investigation, based on interviews with eight initial case-patients, didn't reveal a common exposure.

However, the health team was suspicious that the illnesses might have a connection to Germany's E coli O104:H4 outbreak, because, as in Germany, most of the patients were women. A follow-up survey to provide a more in-depth picture of the vegetables patients ate within 2 weeks before getting sick found that in 11 of 15 suspected cases the patients had attended the same event at a children's community center where several fruits and vegetables were served, including sprouts.

Foodborne illness experts have said sprouts are difficult to tease out in illness investigations, because they often aren't noticed when tucked into sandwiches or used as an ingredient or garnish in salads or other food items.

At the community center events, fenugreek sprouts were served with soups and placed on platters of crudites on the buffet. Mustard and rocket sprouts, still growing on cotton wool, were used to decorate the crudites. Of 11 patients with links to the center, nine who were well enough to be questioned said they had consumed sprouts.

Trace-back studies found that the three types of sprouts had been grown at the center to be served at the event. The seeds were bought from a national gardening retail chain which got them from a United Kingdom distributor. Tests are under way on leftover rocket and mustard seeds from the center, as well as gazpacho and water. Lab officials are testing mustard, fenugreek, and other seeds from the French retailer.

When laboratory experts compared isolates from three Bordeaux patients who consumed sprouts with samples obtained earlier from two of France's imported E coli O104:H4 cases, they found that the strains were genetically related, with a profile that didn't match two E coli O104:H4 strains that were isolated in 2004 and 2009. They reported that comparisons using whole-genome sequencing and optical map tests will be conducted in upcoming days.

The French researchers said a case-control study and further trace-back investigations are under way, and they warned that other similar outbreaks in France or elsewhere in Europe could occur.

In other developments, South Korean researchers reported today that an E coli O104:H4 isolate from an infected South Korean patient with HUS in 2004 does not match the current outbreak strain. They said the findings, published today in Emerging Infectious Diseases, suggest the South Korean strain is not related to the current European outbreaks.

The South Korean strain was previously the only documented E coli O104:H4 strain. The researchers said they found several differences between the two strains. For example, they said the earlier strain doesn't have the enteroaggregative determinant.

Meanwhile, the European Centre for Disease Prevention and Control (ECDC) said today it has received 22 more E coli infection reports, three of them with HUS. No new deaths were reported. Europe's outbreak total is 4,077 cases, including 888 with HUS and 48 deaths.

See also:

Jun 30 Eurosurveillance report

Jun 30 Emerg Infect Dis report

Jun 30 ECDC update

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