How do you stop the deadly E. Coli bacteria? How about attacking it with a virus? Researchers studying a natural enemy of E. Coli say it could help prevent outbreaks like the one spreading across the country, as this ScienCentral News video reports.
E. Coli Enemy
People may think of E. Coli poisoning as a beef-eater's disease, but the outbreak linked to raw spinach is a tragic reminder that the bacteria often spread through animal droppings into produce growers' water, soil or fertilizer. The illness can't be treated with antibiotics, and while many infected people recover, some develop life-threatening complications.
"They can't really treat you other than to try and let your body fight the disease," says microbiologist Andrew Brabban. "This is why we've taken the approach of not trying to develop a treatment for humans but a treatment for animals so it never appears in the human's diet.
Brabban and his colleague Betty Kutter want to kill the nasty bug at its source, in the intestines of livestock, using a virus that's a natural enemy of E. Coli. The researchers at Washington's Evergreen State College discovered it when their students were studying E. Coli in sheep at the USDA Food and Feed Safety Research Unit. "Every time they tried to infect the sheep with E. Coli, the sheep seemed to be within two days perfectly happy and they couldn't find the bacteria," says Brabban. "They had some natural resistance."
It turned out that the resistant sheep harbored a virus called a phage that specifically preys on E. Coli bacteria. "A phage is a virus that specifically infects a bacterium so it can't infect people and it can't infect animals and it can't infect plants. And not only that, but each phage attacks particular kinds of bacteria," Kutter explains. A phage attacks its host bacterium by injecting its DNA into the bacteria cell. New phages multiply inside and eventually burst through the bacterium, killing it.
As they report in the journal, Applied and Environmental Microbiology, the phage they isolated from the sheep, called CEV-1, kills many strains of disease-causing E. Coli in laboratory cultures.
Using phages to combat harmful bacteria is a case of renewed interest in an old field, points out Kutter. "Phages were first discovered in 1917. They were used a lot during the next 30 or 40 years before antibiotics were available but they sometimes worked very well and they often didn't work at all because people didn't understand that there were different types of phages and they didn't know how to identify which phages worked with which bacteria and so forth," she says. "But then once antibiotics came along in the Western world people almost entirely stopped using phages."
Phage therapy actually continued in the Soviet Union and the Evergreen team is collaborating with researchers at the Eliava Institute in Tbilisi in the Georgian Republic to revive and advance its leadership in treating severe bacterial infections in people.
Electron microscope image of a phage
Brabban and Kutter's goal is to develop a phage cocktail that can be given orally to livestocks to eliminate dangerous strains of E. Coli in their intestines. "We'd simply give it to them in their food or in their drinking water," says Brabban.
That may take years of research, because "what happens in the intestines is very different from what happens in a test-tube," Brabban says. "It seems to be that E. Coli in general is a very small component of intestinal flora, actually less than one percent. So we need to try to develop a system to kill it at very low concentrations."
Since the phage works so well outside the animals, Brabban says it may be possible to develop it as a mist or spray to treat produce before it can be used to treat animals. In August, the Food and Drug Administration (FDA) approved the first-ever phage treatment to kill a different bacteria -- listeria -- on foods. Brabban says that because it takes so few E. Coli bacteria to cause disease, the challenge is to make sure any treatment kills all the E. Coli, whether in animals or on fresh foods.
"All you need is from 10 to 100 live cells of E. Coli 0157 to cause disease, a tiny number," says Brabban. "Compare that to cholera bacteria where you need to ingest a million cells" to contract the disease.
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