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Toxic E. coli strains emerge from other strains pooling poison in cow intestines: research

The main gate of Kyushu University Faculty of Medical Sciences is seen in this file photo taken on Feb. 20, 2015. (Mainichi/Toshiyasu Kawachi)

FUKUOKA -- Types of Escherichia coli (E. coli) that cause gastrointestinal illness in people, including the powerful O157 strain, originate from other forms of the bacteria that have accumulated toxic substances inside the cow intestines where they live, a Kyushu University-led research team has found.

The research result, based on genomic analysis, is drawing attention as it could lead to development of measures to prevent enterohemorrhagic E. coli (EHEC) infection.

It is known that cattle carry EHEC bacteria and that infection can spread from dung and the animals' intestines when they are slaughtered. Researchers including Yoshitoshi Ogura, associate professor of genome science at Kyushu University's Faculty of Medical Sciences, conducted comparative genomic analysis on a total of 1,134 strains of E. coli in humans, non-toxic E. coli in cattle and EHEC.

Researchers found genetic differences in E. coli collected from humans and cattle. It was revealed that the bacteria in cattle intestines accumulate substances toxic for humans and turn into E. coli types such as O157 and O26, another highly toxic strain. The bacteria may be accumulating toxic substances to avoid being eaten by other microorganisms in the cow's intestine.

The research team says it is possible to reduce the development of EHEC and prevent infection by identifying what prompts the change from non-toxic E. coli to highly toxic E. coli.

Genomic analysis was conducted by researchers in Japan, the United States, France and Belgium, and the results were published in the electronic edition of the American scientific journal Genome Research on Aug. 23.

(Japanese original by Hiroshi Mahara, Kyushu News Department)

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