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Why a lucky few may be immune to food poisoning

Scientists believe they've discovered genes that may protect some people from E. coli.
/ Source: TODAY

Ever wonder why only some folks become ill during a food poisoning outbreak? Of course, they may not be eating the same foods that made other people sick, but new research suggests another possible reason: some of us may just be more resistant to certain stomach bugs.

Some people's bodies are able to clear out E. coli bacteria without getting sick. But it's unclear why they're the lucky ones.
Some people's bodies are able to clear out E. coli bacteria without getting sick. But it's unclear why they're the lucky ones.Mark Dubowski for Duke Health / Mark Dubowski for Duke Health

Resistance to one of the most pernicious bugs, E. coli, may come down to what’s written in someone's DNA, according to a small study by Duke University researchers, published in the Journal of Infectious Diseases.

“These are people who, despite being exposed to E. coli and even when they are shedding E. coli, their bodies respond in such a manner that that they don’t get sick,” said study coauthor Ephraim Tsalik, an assistant professor at Duke University and at the Durham VA Medical Center. “What’s harder to answer is what it is about them that allows them to clear the bacteria without getting sick.

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To get a better sense of what genes might be involved in fending off the bacteria, researchers drew blood samples from 30 healthy volunteers and then asked them to drink a slurry containing E. coli. Several days later, six of the volunteers had developed severe symptoms typical of food poisoning, while six others had no signs whatever of their exposure to the bug. The other 18 developed mild to moderate symptoms.

When they compared the gene expression of those who had no symptoms to those who got very sick, the researchers found significant differences in the activity of 29 immune-related genes. And just looking at those differences could predict who would become sick and who would not.

Tsalik’s research team has also used the technique to look at respiratory viruses. In those experiments, the researchers found that about 50 percent of people fought off the bugs with nary a sign of illness.

While some of the genes involved in warding off E. Coli are the same as those involved in fighting respiratory bugs, some appear to be specifically pointed toward the bacteria, Tsalik said. So that means if there were a similar study of the norovirus, which can also lead to intestinal misery, different genes might be involved.

The new study is “intriguing,” said Dietrich Stephan, a professor and chairman of the department of human genetics at the University of Pittsburgh. “But the numbers are really small. It needs to be replicated in a much larger study. I’d like to see one with hundreds of patients.”

Still, Stephan said, “It suggests some of us may have a baseline immune system that is a little more revved up and specifically protective of E. coli gastrointestinal infections.”

Pinpointing the infection-resistant genes might one day lead to a test to determine who is most at risk during a foodborne outbreak. And that might help doctors figure out whether someone who is currently asymptomatic should be given preventive treatment, Tsalik said. Right now, there’s precious little people can do to avoid becoming ill.

Meanwhile, if you suspect you've eaten food contaminated with E. coli, here's what you need to know:

  • It usually takes three to four days from the time you’ve ingested contaminated food until you start showing symptoms, though it can take a little longer if there was only a small amount of bacteria in what you consumed.

  • The first signs of bacterial food poisoning can be cramps and diarrhea, which can turn bloody.

  • Only a small percentage of cases turn out to have very serious complications.

  • If you do develop symptoms you should contact your doctor right away. Early medical care is extremely important.