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Researchers developing way to distinguish between salmonella strains:
Penn State Live Tuesday, September 21, 2010
University Park, Pa. — As scientists with the federal government search for the source of the salmonella that made thousands of people sick this summer and trace how it spread, researchers in Penn State's College of Agricultural Sciences are developing a new and more accurate method of acquiring the bacteria's identity.
The outbreak began last May. By August, at least 1,000 more people than usual around the country had gotten sick with salmonella poisoning. Investigators from the Food and Drug Administration discovered that two large enterprises in Iowa supplied eggs that carried a common type of salmonella, Salmonella Enteritidis, frequently associated with eggs. More than 500 million eggs from those farms were recalled, and investigators are piecing together how the outbreak occurred.
Hospitals reported the cases to state health authorities, who took a kind of genetic fingerprint of the bacteria and passed that information along to the Centers for Disease Control and Prevention in Atlanta. But in this case, the genetic fingerprint wasn't very helpful for tracing the bacteria because it was the most common fingerprint for Salmonella Enteritidis in CDC’s database.
As a result, "Investigators couldn't tell if all those people really got sick from the same thing," said Stephen Knabel, professor of food science, who has been working with faculty colleague Edward Dudley for the past year to develop a new and more accurate method for DNA fingerprinting the top 10 types of salmonella bacteria.
"The problem is that different strains of Salmonella Enteritidis are highly related and very difficult to distinguish between," Knabel said. "The CDC uses a method of DNA fingerprinting called PFGE to track the strain that caused the outbreak, but it doesn't work so well with Salmonella Enteritidis."
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