WASHINGTON, D.C., May 29, 1997--A staple of summer, the common housefly, may be a reservoir for Helicobacter pylori, the bacterium responsible for some types of ulcers and associated with stomach cancer, say researchers from St. Elizabeth's Medical Center of Boston in the June 1997 issue of the Journal of Clinical Microbiology. This study is the first report of H. pylori colonization of houseflies.
"The mode of transmission of Helicobacter pylori is unknown," says Peter Grbel, one of the authors of the study. "Since viable bacteria have been shown to be excreted in feces from infected individuals and houseflies habitually develop and feed on excrement, we hypothesized that flies ingest and harbor H. pylori and in turn contaminate the human environment."
In the study the researchers exposed groups of adult houseflies to either a culture of the bacteria or a sterile control plate. After exposure, flies were removed from both the sample and the control group and tested at intervals of six hours for the presence of the bacteria on their skin, in their digestive tract, and in their excretions.
The researchers found the bacteria present on the skin of the exposed flies for up to 12 hours. In addition, the exposed flies had bacteria in their gut and their excretions for up to 30 hours after exposure. The control group had no presence of the bacteria.
"We postulate that H. pylori is acquired from human excrement by the housefly, which then, while crawling on human food, contaminates it," says Dr. Grbel.
H. pylori is a bacterium that was first described in the early 1980's by a group of Australian researchers who theorized its connection to ulcers. It is the cause of most duodenal ulcers and an estimated 70-80 percent of gastric ulcers. In the late 1980s researchers at Stanford University showed it was associated with certain types of stomach cancer.