Carried by Cattle

Escherichia coli are bacteria that live in the intestines of people and animals. Most are harmless. But the strain identified as O157:H7 can make people sick.

Carried in the forestomachs and intestinal tracts of healthy cattle, the bacterium gets into ground beef by fecal contact.

It has plagued the country's food industry in recent years, showing up in raw milk, roast beef, apple cider, salami and even vegetables.

Good Guys vs. Bad Guys

UGA scientists are taking a "fight fire with fire" approach. They are squelching the deadly germ with "good" bacteria.

Doyle said they first tried to develop a vaccine. "But we found that because of the way the bacterium localizes in the three forestomachs in cattle, the vaccine was not going to work," he said. So they turned instead to a "probiotic culture."

"We examined about 1,200 bacteria isolated from cattle that didn't have E. coli 0157:H7," Doyle said. "We looked for beneficial bacteria that prevent the bad bacteria from being carried in the intestinal tract of cattle."

Virtually Eliminating E. coli O157:H7

They isolated 18 strains of the good bacteria they were looking for, he said. From these, the scientists produced a culture they fed to cattle which were then infected with the bad germs.

"We found that in two to three weeks, it will virtually eliminate the shedding of E. coli 0157:H7," he said. They found similar results when cattle previously infected with the E. coli were fed the good bacteria.

Doyle said the pathogen wasn't just reduced in the fecal matter. "We couldn't find it in the rumen, either," he said.

The Future Looks Bright

But the fecal matter is the source of most E. coli contamination of food products. The UGA finding could dramatically reduce one of the nation's most feared foodborne illnesses.

Eventually. It has a long way to go yet, Doyle said. Before it can approach its potential, the U.S. Food and Drug Administration has to approve it. Then a commercial product has to be developed from the culture, for which UGA has applied for a patent.

Similar Research on Poultry

U.S. Department of Agriculture scientists in Athens, Ga., are already seeking approval for a similar product, Doyle said.

"They're applying for approval of a 'competitive exclusion culture' for poultry," he said. The USDA culture could rid chickens' intestines of Salmonella, another common cause of foodborne illness.

Doyle's past studies have uncovered ways to detect E. coli 0157:H7 faster and decontaminate many food products. But the pathogen is becoming even more widespread.

Cattle Not the Only Carriers

"There's more to the equation than contamination in food processing," he said. "0157 is picked up by other animals. It's been found in sheep and goats. Children have been infected in petting zoos. Manure is another problem."

It's vital, Doyle said, to stop the deadly pathogen at its main source. "We need to reduce the carriage of E. coli 0157:H7 in cattle," he said.

(Article by Dan Rahn,University of Georgia College of Agricultural and Environmental Sciences. Cattle photograph by Scott Bauer, USDA. E. coli photograph courtesy UGA Center for Food Safety)

Aug. 25, 1997