Finding May Lead to Vaccine for Traveler's Diarrhea

WEDNESDAY, June 10 (HealthDay News) -- Montezuma's revenge, also known as traveler's diarrhea, can ruin a vacation.

Now, researchers have figured out how the bacteria responsible for the illness -- enterotoxigenic Escherichia coli, or ETEC -- are able to make you so miserable.

The bacteria use surface "pili" or "fimbriae" to attach, or bind, to the intestinal epithelia of the host. These fibers, which are needed for ETEC infection to take place in the intestines, exit the bacterium through a pore on the bacterial surface, the researchers explained in a news release from the Boston University School of Medicine.

"Atomic resolution detail of the proteins in the fibers and analysis of genetic variability among different clinical strains were combined to show that each bacterial strain presents a different outer surface of the major protein while preserving the protein components that are buried within the fiber," the study's senior author, Esther Bullitt, an associate professor in the department of physiology and biophysics at Boston University School of Medicine, said in the news release.

"Because of this, the antibodies produced against ETEC during one episode of infection are often not protective against later infections by other strains," she added.

Developing a cross-protective vaccine will require a strategy that focuses on use of the tip protein as an antigen, according to the study, which is published in this week's issue of the Proceedings of the National Academy of Sciences.

"The structural findings reported here have bearing on research to help guide vaccine development," the researchers said in the news release.

ETEC bacteria cause the largest number of community-acquired cases of childhood diarrhea in the developing world and are the most common culprit in traveler's diarrhea, according to the World Health Organization.

ETEC bacteria are transmitted by food or water contaminated with animal or human feces. Infection occurs when a person eats food or drinks water or ice contaminated with ETEC bacteria.

Infection with ETEC can cause profuse watery diarrhea and abdominal cramping. Fever, nausea with or without vomiting, chills, loss of appetite, headache, muscle aches and bloating can also occur but are less common.

The illness develops one to three days after exposure and usually lasts three to four days, although some infections last more than a week, but it is rarely life-threatening.

-- Jennifer Thomas

SOURCE: Boston University School of Medicine, news release, June 8, 2009

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