Is this a bug we should love?

Julie Parsonnet

More than half of the world's population is infected with Helicobacter pylori, but scientists are still trying to determine whether this is a big problem--or a hidden blessing.

Although H. pylori has been implicated as a culprit in causing stomach cancer and ulcers, there is evidence that it may protect some people from cancer of the esophagus and the intestinal disease gastroenteritis, often referred to as the "stomach flu."

For years, Julie Parsonnet, MD, professor of infectious diseases and geographic medicine and of epidemiology, has been exploring the relationship between H. pylori and other diseases. And now she has a study under way to determine the bug's potential benefits.

To see if it provides a protective effect against gastroenteritis, Parsonnet's group is currently enrolling healthy adults between the ages of 35 and 59 years in a study. They are looking both for people who have been exposed to H. pylori and those who have not so they can compare how the two groups respond to exposure to another bug.

Screening for participants will include a physical exam and a few routine health tests, including a blood draw, which lasts about an hour. Participants will be paid $30 for the screen. If eligible, participants may then be asked to continue on in a three-day study at Stanford Hospital for which they will receive up to $320.

The study involves ingesting a dose of Escherichia coli, a normal bacterial inhabitant of the human intestinal tract. Some strains of E. coli can cause infections, including gastroenteritis. Symptoms of gastroenteritis can range from a mild bout of indigestion to diarrhea, abdominal cramps and nausea or vomiting, which usually resolve in a day or so. Stool samples will be collected throughout the three days to track the course of the infection.

The study will also measure the stomach acidity levels of the participants. One possible explanation for how H. pylori might exert a protective effect is that in some people the bacterium might increase gastric acid output, killing the organism. H. pylori might also increase the immune responses of the intestinal tract, wiping out organisms before they can do much damage.

For more information, or to sign up to be screened, please call 724-4941.