Faster Test Detects E. Coli Bacteria
Scientists at the University of California-Davis have developed a new, faster test for detecting E. coli O157:H7, the bacterium that this year killed 11 Japanese in a single outbreak and killed three Washington state children in 1993.
Announced this week, the test detects the bacteria in meat and dairy products and requires about eight hours to complete. Other tests take as long as two days.
“It’s more rapid and reliable. … Its value is in reducing the chance of bacteria at critical points in production,” said Prabhakara Choudary, director of the UC-Davis Antibody Engineering Laboratory. Choudary and another Davis researcher, Christopher Gooding, created the test.
The test is performed in several steps: Magnetized beads the size of a pinpoint are coated with E. coli O157:H7 antibodies and placed in a sample of milk, liquid ice cream or liquefied meat. The beads attract the bacteria, a magnet pulls the beads to the side of the vial, and the rest of the liquid is poured out.
Next, the “captured” bacteria are put through “PCR amplification,” a procedure that enables the lab to make millions of copies of certain segments of DNA the two E. coli O157:H7 genes responsible for the organism’s powerful toxin. The genes are verified by a process called gel electrophoresis.
“This method could benefit dairy producers as well as food inspectors, since the methodology is not technically demanding, and can be easily and rapidly performed by technical personnel with minimal training,” said Choudary.
Phillip Tarr, an E. coli O157:H7 expert at Children’s Hospital & Medical Center in Seattle, said no test should be used as a substitute for cooking meat well.
“I just don’t want to see a lot of foods out there with labels saying this has been tested,” implying safety, said Tarr.
Choudary agreed, saying the test should be considered only as another tool in helping make meat and dairy products safe.
He said several companies have already expressed interest in commercially producing the test.