Scientists Devise New Test for E. coli O157 in Water
By Sharon Durham
March 6, 2002
Agricultural Research Service scientists
have developed a rapid, easy-to-use test to detect and count E.
coli O157:H7 bacteria in natural and constructed bodies of water. ARS
microbiologists Dan Shelton and Jeff Karns in the
Animal Waste Pathogen
Laboratory, Beltsville, Md., developed the test, which uses magnetic beads
to detect the pathogen.
The magnetic beads are coated with anti-E. coli monoclonal antibodies
that bind to the bacteria, making it possible to count the bacteria. Current
testing methods are designed only to detect the bacteria, but not to measure
how many are present. The number of E. coli bacteria present is crucial
information since the levels that cause infection can vary from person to
person, depending on the persons health status. Also, the new method
makes it possible to detect E. coli in water samples in a day or less,
compared with traditional testing that can take up to four days to complete.
Usually spread in contaminated food, E. coli is sometimes waterborne.
In 1998, an E. coli outbreak occurred at an Atlanta, Ga., water park,
causing the hospitalization of several children. E. coli can cause
diarrhea, hemorrhagic colitis and hemolytic uremic syndrome (HUS). HUS can
result in destruction of red blood cells, damage to the lining of blood vessel
walls and, in severe cases, kidney failure.
Investigations are under way to assure no other bacteria cross-react with
the magnetic beads. However, if this test proves to be accurate and selective,
it should allow for detection of E. coli in a variety of liquid samples,
such as swimming pools and other recreational water.
ARS is the U.S. Department of
Agricultures chief scientific research agency.