Can houseflies spread the ulcer bacterium.

Ten years ago, the standard prescription for an ulcer would have been an antacid and a bland diet. Today, it's an antibiotic.

It took a long time for the notion that a microbe causes ulcers to catch on, and one of the reasons was the setting. The stomach was considered too acidic for anything to inhabit.

Researchers have now found another place where Helicobacter pylori, the ulcer-causing bacterium, can live--on the body and in the gut of houseflies. Although the flies did not acquire the microbe in a natural setting, the researchers say that the finding, reported in the June Journal of Clinical Microbiology, raises the possibility that the insects can sometimes transmit the organism. If so, it may explain part of the intriguing epidemiology of H. pylori infections.

After working in Africa for a year, Peter Grubel, a gastroenterologist at St. Elizabeth's Medical Center in Boston, was prompted to look into the possibility that flies transmit the bacterium.

He wondered whether the constant presence of the insects might have something to do with the high rates of H. pylori infections in developing countries, where 60 to 70 percent of the population can be affected. In the United States, about 30 percent of the population shows signs of the infection.

There's also a generational difference in developed countries. H. pylori infections, including ulcers and some gastric cancers, are prevalent among older adults but rare among children. In developing countries, most children are infected by age 10.

How the infection spreads hasn't been clear, although scientists have generally thought that the bacterium travels the same fecal-oral route as salmonella and other pathogens that can be transmitted by flies.

Grubel and his colleagues set up an experiment to see whether H. pylori can indeed live on the housefly. They let disinfected flies feed on petri dishes covered with H. pylori and collected some of the insects every few hours to analyze.

The researchers were able to grow in the laboratory H. pylori from the flies' bristly outer surfaces, gut, and droppings. A portion of the fly's gut is as acidic as the human stomach. "H. pylori may find a very good niche in flies," says Grubel.

He and his coworkers are now beginning to develop a method for detecting the bacteria on flies taken from a natural setting. Grubel says flies could be involved in spreading the infection in areas with poor sanitation. The insects may also have contributed to the prevalence of H. pylori in people born before indoor plumbing became standard in postwar European and U.S. households, he says.

"It is a provocative theory," says Barry J. Marshall of the University of Virginia Medical School in Charlottesville, who helped make the connection between the bacterium and ulcers in 1983.

Flies probably aren't the final answer to the question of ulcer transmission says microbiologist Martin J. Blaser of Vanderbilt University Medical Center in Nashville. "Smart organisms like Helicobacter have figured out a lot of different ways to get transmitted," as has HIV, he says. "I don't think transmission relies on one route."

Hand washing, or the lack thereof, very likely plays a key role in the spread of H. pylori, he adds.