Scientists probe DNA of E. coli for outbreak clues

Jun 13, 2011 By MARIA CHENG , AP Medical Writer

(AP) -- Scientists are quickly combing the DNA of the killer bacteria behind the world's worst E. coli outbreak to find clues about how to treat patients and prevent future epidemics.

So far, one strain from a German patient has been sequenced by Chinese and German scientists. While the is preliminary, experts say there are a few hints about where the came from and why it might be so lethal.

The E. coli causing Europe's massive outbreak is likely the product of another strain first detected a decade ago in Germany, but with some dangerous mutations, experts say. German investigators have declared the outbreak was caused by contaminated from an in northern Germany. So far, the bug has killed at least 35 people and sickened more than 3,000, including several hundred who have developed life-threatening .

Flemming Scheutz, head of the World Health Organization's Collaborating Centre laboratory in Denmark, said the strain is particularly good at picking up new genes. Because E. coli is constantly evolving, it is riddled with genes swapped from other strains found in animals and humans, giving it countless opportunities to acquire something lethal.

"It's just very unfortunate that in this case, it recombined and took on these (dangerous) genes and that it happened to do it in the food chain," he said.

Scheutz said some previously seen related strains were also quite toxic but that scientists needed more samples to have a better understanding of how the new strain behaves. "It's like looking at a family photo with three people and the 50 others are missing," he said.

Others say the they've seen so far appear worrying enough.

Stephen Smith, a at Trinity College in Dublin, said the new E. coli appears to stick to human intestines in a different way and that the bacteria might reproduce faster than other E. coli strains. More bacteria in the intestines could explain why the disease is so deadly, he said. Smith was not involved in the sequencing work.

"It could be the bacteria's genes are causing it to produce more toxin, which may affect patients differently," he said. The toxin usually targets the kidney, triggering a severe E. coli complication. But in the European outbreak, many of those patients have also suffered from neurological problems including paralysis.

Frederick Blattner of the University of Wisconsin, who has analyzed the new sequence information, said the toxin released by the German E. coli seemed extremely potent.

"With other strains, it can take a million of them in your stomach to make you sick," he said. "But with this bacteria, it might be possible to be infected with much lower numbers."

Researchers have also found the E. coli bacteria has at least eight genes that make it resistant to many antibiotics.

"That could give suggestions to doctors about what treatments to select for patients," said Bicheng Yang, a spokeswoman for BGI, the Chinese laboratory that sequenced the bacteria. In Germany, many patients with the most severe form of the disease, which involves kidney failure, have been treated with dialysis and blood transfusions.

"The next step is to do further tests at the molecular level to see what drugs might work," she said. Yang added that knowing more about the bacteria's origins could help stop future outbreaks and avoid things that could speed up the mutation process.

Gad Frankel, a microbiologist at Imperial College in London, said DNA information might help scientists figure out how the bacteria sticks to certain vegetables - and then stop it before it happens. "It's possible we could develop inhibitors to prevent the interaction between E. coli and vegetables," he said, explaining a biodegradeable spray could theoretically be made to do the job.

Experts agreed that narrowing down where the new E. coli came from was key to averting future epidemics. "The evolution of E. coli just happens when bugs get together," Smith said. "We can't stop evolution, but if we can learn today how and where it happens, we might be able to save lives in the future."

Explore further: Oral contraceptive equal to antibiotics for acne care

not rated yet
add to favorites email to friend print save as pdf

Related Stories

Resistant gut bacteria will not go away by themselves

Jun 19, 2007

E. coli bacteria that have developed resistance to antibiotics will probably still be around even if we stop using antibiotics, as these strains have the same good chance as other bacteria of continuing to colonise the gut, ...

Viruses can turn harmless E. coli dangerous

Apr 16, 2009

For her doctorate, Camilla Sekse studied how viral DNA can be transmitted from pathogenic to non-pathogenic E. coli. Viruses that infect bacteria in this way are called bacteriophages. Her findings reveal ...

Germany still seeking reason for E. coli outbreak

Jun 13, 2011

(AP) -- German authorities said Sunday that they haven't yet been able to resolve how sprouts at a farm became contaminated with an aggressive strain of E. coli that has been blamed for 35 deaths.

Disease-causing Escherichia coli: 'I will survive'

Sep 09, 2009

Strains of Escherichia coli bacteria that cause food poisoning have been shown to have marked differences in the numbers of genes they carry compared to laboratory strains of E. coli. Some of these genes may enable them t ...

Recommended for you

Oral contraceptive equal to antibiotics for acne care

5 hours ago

(HealthDay)—At six months, oral contraceptive pills (OCPs) are comparable to systemic antibiotics for acne management, according to a review published in the September issue of the Journal of the American Ac ...

Photodynamic therapy vs. cryotherapy for actinic keratoses

6 hours ago

Photodynamic therapy (PDT, which uses topical agents and light to kill tissue) appears to better clear actinic keratoses (AKs, a common skin lesion caused by sun damage) at three months after treatment than cryotherapy (which ...

US official warns Ebola outbreak will get worse

8 hours ago

A third top doctor has died from Ebola in Sierra Leone, a government official said Wednesday, as a leading American health official warned that the outbreak sweeping West Africa would get worse before it ...

UN releases $1.5mn to help DR Congo fight Ebola

10 hours ago

The United Nations on Wednesday allocated $1.5 million (1.1 million euros) to help the Democratic Republic of Congo fight Ebola, just days after the country confirmed its first cases this year.

User comments : 0