Bug uncovered

时间:2019-03-06 02:14:18166网络整理admin

By Emma Young The genome of a potentially deadly strain of Escherichia coli 0157 has been sequenced by a US team. The work has thrown up “shocking” surprises which help explain how the bacteria kills, and may lead to more effective tests and treatments, says Nicole Perna of the University of Wisconsin-Madison, who led the research. E. coli 0157:H7 produces toxins that cause bloody diarrhoea and kidney failure. It is mainly transmitted in infected meat and was responsible for the world’s worst outbreak of E. coli food poisoning, killing 20 people in Scotland in 1996. In the US, it causes an estimated 75,000 infections every year. The team found that E. coli O157:H7 is armed with an extraordinarily wide range of genes that help it trigger disease and resist destruction by the body. “Better ways to diagnose, treat and prevent E. coli 0157:H7 infections are badly needed,” says Anthony Fauci, director of the US National Institute of Allergy and Infectious Diseases, which part-funded the research. “This new information will provide important leads to scientists.” Hugh Pennington of Aberdeen University, who led an inquiry into the 1996 Scottish outbreak, says: “This is very nice work. But it really whets the appetite. We now need lots of other people to look at genome sequences of other strains of E. coli 0157 to find out how universal some of the newly identified genes are.” The researchers compared the DNA from a sample of O157:H7 isolated during a 1982 outbreak with the previously sequenced genome of a benign strain of E. coli. The researchers were surprised by the vast differences between the two E. coli genomes. The two strains share about 3,500 genes. But the O157:H7 strain has 1,300 additional genes – the benign strain has just 530 extra. “The sheer magnitude of the differences was totally shocking to us,” says Perna. It suggests that E. coli strains pick up new DNA at a very rapid rate. The DNA unique to each strain was probably deposited by invading viruses, says Guy Plunkett, one of the researchers. “But quite why E. coli picks up foreign genes so readily we don’t know. It could be that this bacteria is more prone to infection, or it could be something about their DNA metabolism that means when foreign DNA enters it is not destroyed,” he told New Scientist. This rapid evolution helps explain how E. coli as a species is so versatile, says James Kaper at the University of Maryland. “It can be found normally in human intestines and is also capable of causing a variety of infections, from urinary tract infections to diarrhoea to neonatal meningitis. This paper will provide important insights into how a pathogen becomes a pathogen.” The genome sequence should also provide new targets for diagnostic tests, says Plunkett. And the detection of genes that probably code for previously unidentified toxins may aid the development of an effective vaccine or treatment, he says. More at: Nature (vol 409,