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 ore than 75 million people per year become ill from
food poisoning in the United States, 325,000 are hospitalized,
and 5,000 of them die from pathogens like Salmonella and E.
coli. But detection of these pathogens is getting easier,
thanks to several new biosensors developed by researchers at
the University of Rhode Island.
 Ten
years in development, the biosensors use fiber optic technology
to quickly and accurately detect and quantify bacteria levels
in meats, poultry and other foods.
"There
are about 6,000 meat and poultry processing plants in the United
States, and they all are required by law to test their products
for food pathogens," said A. Garth Rand, professor emeritus
of food science at URI. "Most of these plants don't have
their own labs, so they've got to send their samples out to commercial
labs. Instead of waiting several days to get results, they can
use our biosensor and have results in an hour."
Rand teamed
up with Stephen Letcher, professor of physics, and Christopher
Brown, professor of chemistry, to establish the URI Fiber Optic
& Biosensor Research Group to tackle the difficult problem
of developing a fast and sensitive food pathogen sensor.
This research
group is part of the University's Sensors and Surface Technology
Partnership. The US Department of Agriculture has funded the
research for the past eight years. "We are one of a very
small number of research groups working on food safety biosensors,"
said Rand. "And our combination of disciplines is unique.
The only way to solve this kind of problem is with an interdisciplinary
approach."
Focusing first
on detecting Salmonella, one of the most common food pathogens,
the group developed several sensors that use vibrating quartz
crystals or fiber optic probes along with Salmonella antibodies
that bind the pathogen cells to the sensor. The latest version
also uses microscopic magnetic beads called microspheres.
"The
surface of the beads are covered with antibodies that collect
the pathogen and are then labeled with a fluorescent dye,"
explained Rand. "Then the beads are magnetically focused
in front of optical fibers and a laser signal reports the pathogen
concentration."
The binding
of the pathogen cells to the antibodies takes about 60 minutes,
while the process of determining the pathogen concentration takes
just 60-90 seconds.
Although the
sensor needs further refinement before it is complete, the researchers
are working with Pierson Scientific Associates of Andover, Mass.,
to develop portable prototypes of the device. The partnership
was awarded a Small Business Technology Transfer grant from the
National Science Foundation in 1998.
"While
we've been primarily studying Salmonella, the system works for
most other food pathogens, too," Rand said. "In fact,
we believe it works even better for E. coli."
The URI researchers
have also been working on biosensors for the US Army Natick Labs,
which prepares Defense Department meals that are often stored
for years in remote locations. The Army has funded Rand's research
into developing sensors to detect pathogens in Army rations.
"They
are especially concerned with detecting pathogens that grow in
low-moisture dried foods," explained Rand. "They needed
a quick way to see if pathogens are growing in the food they
have stored around the world." For this project, Rand's
team developed a membrane biosensor. When the membrane is coated
with antibodies and enzymes, the bacteria gets caught on the
membrane while the rest of the solution being tested passes through
it. Next up for the URI researchers is the creation of a hand-held
surface scanning system - similar to a supermarket checkout scanner
that uses video to detect the pathogens, and another that detects
pathogens in seafoods.
"These
sensors will significantly enhance the safety of the food supply
and protect human health," concluded Rand. 
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