November 18, 1999
Using tools from research in developing countries, a Tulane study of day-care centers in New Orleans has shown that the Escherichia coli bacterium is not a major cause of diarrhea in children in daycare settings here.
Richard Oberhelman, clinical associate professor of tropical medicine, followed 112 children in five centers for one year to examine the role of E. coli in diarrheal illnesses in day-care settings in this country. He used his experience studying diarrheal diseases in children in developing countries to explore an area about which researchers knew little.
"Diarrheal diseases are caused by viruses, parasites and bacteria," Oberhelman says. "Bacterial pathogens, such as certain types of E. coli, have been looked at in developing countries such as Peru, but we haven't studied them here."
Oberhelman, who has studied these diseases in Peru, Mexico and Nicaragua, says that diarrhea-causing bacteria aren't researched more extensively in this country because they require special laboratory techniques for identification.
"It was interesting to me because most of my work is overseas and it was an opportunity to use some of the tools that we developed overseas and use them here," he says. "It's a reverse transfer of technology. And while diarrheal diseases aren't nearly as devastating in this country as they are in the developing world, these types of infections run a close second to respiratory infections as the most common communicable diseases in day-care settings in this country," he adds.
The study, which was funded by the Louisiana Board of Regents, began in November 1994 after Oberhelman's research team had canvassed the day-care centers in the city and found five that were willing to participate in the study for the entire year.
After gathering demographic information about the families and center practices, study nurse Phyllis Saunders collected stool samples every two weeks from children ranging in age from 6 weeks to 24 months. With regular stool samples, researchers analyzed them in the lab for the presence of E. coli. With samples of diarrhea, the research team analyzed the stool for other causes of diarrhea in addition to E. coli.
Evaluating the 18 episodes of diarrhea detected during the year, the researchers found one strain of E. coli was present in both sick and well children. This strain was enteradherent E. coli, which is increasingly associated with chronic diarrhea in developing countries, Oberhelman says. Researchers detected no evidence of the highly toxic enterohemorrhagic E. coli in any of the stool samples. This strain of the bacterium produces bloody diarrhea, stomach cramps and vomiting and periodically makes the news when there is an outbreak in hamburger meat or other foods.
A third type of E. coli, called enterotoxigenic, was found in a small percentage of samples (5 percent of well and 5 percent of sick children). This toxin-producing E. coli is not as dangerous as its enterohemorrhagic cousin, although it causes what is commonly called travelers diarrhea.
Oberhelman theorizes that the healthy children fought off an early infection of the bacterium and traces of it stayed in their bodies. Oberhelman says the day-care centers in the study were representative of the New Orleans population.
"One of the major benefits of this study is the research team's experience testing for E. coli," Oberhelman says. "We now have the resources and the capabilities to do E. coli testing here and if outbreaks occur in centers we can certainly help investigate," he says.
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