Researchers hope to pinpoint E. coli in food

Tuesday, July 2, 2002

ALBANY, N.Y. -- Scientists are developing a handheld sensor they say would help save lives by quickly pinpointing the presence of a deadly E. coli strain and other harmful germs in food and drinks, in some cases within minutes.

The device has been in development for the past decade, during which time several fatal E. coli outbreaks have occurred throughout the country.

In the largest waterborne E. coli outbreak, at the 1999 Washington County Fair in upstate New York, a young girl and elderly man died and 1,000 people were infected, probably after drinking tainted water.

"This device may help prevent people from getting sick and save money as far as medical treatment goes but the ultimate concern is consumer safety," said Cornell University chemist Richard Durst, who helped developed the test.

Field testing of the new device, which takes eight minutes to detect the lethal E. coli 0157:H7, is scheduled to begin this month.

Each year, an estimated 73,000 Americans get sick from eating undercooked beef and about 60 die, according to the Centers for Disease Control and Prevention. An additional 2,100 people are hospitalized for food poisoning.

Most often, E. coli is the culprit. Harmless forms of the bacterium live in the digestive tracts of humans and animals, but what public health officials worry about is E. coli 0157, a deadly strain that causes severe bloody diarrhea and abdominal cramps and can lead to kidney failure or death.

E. coli 0157 was first identified in 1982 after nearly four dozen people in Michigan and Oregon became ill after eating tainted hamburgers. Since then, infections have been reported in more than 30 countries on six continents.

It can contaminate beef during slaughter and packaging, usually from contamination with cattle feces. People who consume unpasteurized milk and juice or inadequately chlorinated water also are at risk of infection.

Speed essential

Current tests for E. coli use a dipstick method developed by Lansing, Mich.-based Neogen Corp., similar to a home pregnancy test in which presence of the bacteria changes the color of the monitor. A negative sample will display a different color to ensure the test worked properly. Results can take up to a workday to complete.

By then, scientists worry, thousands of people can be exposed to the agent at a public event, or tainted food products can be distributed to hundreds of stores.

"What was needed was a simple field-screening test for rapid and very sensitive detection of E. coli," Durst said. "Speed is important to try to make this a preventive device rather than just a diagnostic one."

Food microbiologist Mike Doyle of the University of Georgia, who was not part of the research, said more tests are needed to determine if the Cornell device can actually detect E. coli 0157 better than traditional methods.

"If it's not as good as the standard cultural procedure test, the downside is you're going to have false negatives, which will give you a false sense of security," Doyle said.

Currently, there are about 1,700 beef processors inspected by the U.S. Department of Agriculture -- fewer than 2 percent of the nation's 100,000 retailers that regularly grind beef. USDA regulations forbid the presence of any E. coli 0157 and inspectors typically destroy an entire batch if a test is positive.

The Cornell device attaches antibodies to the outside of microscopic fat bubbles called liposomes on a test strip. A sample moving up the strip attaches to the antibodies and turns red if E. coli 0157 is present. A negative sample would not change color.

The device, the size of a micro-cassette recorder, then reads the strip and measures the amount of germ present. Durst thinks the device could be used by inspectors at beef plants or by investigators at restaurants, food services and public events.

10 minutes to four hours

Currently, the device can detect very high levels of contamination in less than 10 minutes. To detect smaller levels would take four hours because a larger sample would need to incubate.

Cornell has licensed the device to Grand Island, N.Y.-based Innovative Biotechnologies International Inc., which is working with a public health laboratory in upstate New York to test the technology.

Food and water samples will be tested for E. coli 0157 to compare the device with the lab's standard methods, said president and chief executive Richard Montagna.

Respond to this story

Posting a comment requires free registration: