Researchers identify sequence of deadly E. coli
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The recent outbreak of deadly E. coli in Europe was caused by an entirely new super-toxic strain, Chinese and German researchers said Thursday, after finishing sequencing its genome.
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| A farmer dumps boxes of cucumbers in a greenhouse in Algarrobo, Spain, June 1, 2011. Although German laboratory on Tuesday ruled out Spanish cucumbers as the source for spreading fatal enterohamorrhagic E. coli (EHEC) which has killed at least 16 people within Europe, the previous blame has brought a loss of 200 million euros (287.5 million U.S. dollars) to Spanish agriculture and farmers as nearly the whole Europe and Russia have banned the import of vegetables and fruits from Spain. [Jorge Guerrero/Xinhua] |
By now, 17 Germans and one Swede have been killed after the outbreak, while more than 2,000 people across Europe were sickened. The number of people suffering from serious hemolytic-uremic syndrome (HUS) due to the infection has reached 470 in Germany.
In its latest report, the Beijing Genomics Institute in Shenzhen (BGI-Shenzhen), China's flagship genome center, said it "has just completed the sequence and carried out a preliminary analysis that shows the current infection is caused by an entirely new super-toxic E. coli strain."
BGI-Shenzhen was collaborating closely with the University Medical Center Hamburg-Eppendorf in Germany by using their genomic technology.
The Chinese laboratory said it had finished sequencing the genome of the bacterium upon receiving the bacterial DNA samples, with the help of the third-generation sequencing platform -- Ion Torrent.
"Bioinformatics analysis revealed that this E. coli is a new strain of bacteria that is highly infectious and toxic," BGI-Shenzhen said in the report, adding that the bacterium is an EHEC serotype O104 E. coli strain, which has never been involved in any E. coli outbreaks before.
The new strain was "super-toxic," as it has 93 percent sequence similarity with the EAEC 55989 E. coli strain, which was isolated in the Central African Republic and known for causing serious diarrhea.
Furthermore, it has "acquired specific sequences that appear to be similar to those involved in the pathogenicity of hemorrhagic colitis and hemolytic-uremic syndrome."
The lethal bacterium also carries several antibiotic resistance genes, including resistance to aminoglycoside, macrolides and Beta-lactam antibiotics, all of which makes antibiotic treatment extremely difficult, BGI-Shenzhen said, adding the acquisition of these genes may have occurred through horizontal gene transfer.
Also on Thursday, experts from the University Hospital of Muenster in Germany and Life Technologies Corporation announced their joint research results, saying "the bacterium at the root of the deadly outbreak in Germany is a new hybrid type of pathogenic E. coli strains."
"The data obtained from the DNA sequence shows the presence of genes typically found in two different types of E. coli: enteroaggregative E. coli (EAEC) and enterohemorrhagic E. coli (EHEC)," said Life Technologies' laboratories in Darmstadt, Germany.
"The rapid whole genome sequencing results enabled us to discover within days a unique combination of virulence traits ... and makes this German outbreak clone a unique hybrid of different E. coli pathovars," said Dr. med. Alexander Mellmann, scientist at the German National Consulting Laboratory for Hemolytic Uremic Syndrome (HUS) at the Institute of Hygiene, University Hospital Muenster.
The company has provided the data in record speed, considering the severity of the outbreak, said Simone Guenther, who carried out the sequencing work in Life Technologies.
Life Technologies said the data can be used by scientists at the University Hospital Muenster to develop better tests to positively identify the illness in people showing symptoms of the infection.
