WANT to know if that dodgy takeaway you bought last night gave you food
poisoning? Or was it your lunchtime fish and chips? A clever gadget no bigger
than a personal stereo will not only take the guesswork out of the task but also
give you a rapid answer.
While the gadget, called ImmunoFlow, will at first be used by food-processing
companies, it is so small and light that its inventors ultimately envisage
health inspectors delivering on-the-spot justice to restaurateurs trading in
spoilt chicken or buggy burgers.
Unlike today鈥檚 tests, which can take many days, ImmunoFlow should do the job
in 15 to 30 minutes. Those saved hours could be critical when investigating an
outbreak, says inventor Bart Weimer, a microbiologist at Utah State University
in Logan.
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鈥淲e can now detect bacteria more easily and with better sensitivity than
existing commercial tests,鈥� says Weimer. ImmunoFlow is so sensitive it can
detect Salmonella, Listeria and E. coli
O157鈥攅ven when there are only 100 cells per millilitre.
At the moment, when food inspectors investigate a report of tainted food,
they place the offending morsel in a sterile container and take it to a lab for
analysis. It takes at least 24 hours for any bugs in the sample to grow on a
plate. Sometimes it鈥檚 seven days before they get an answer.
With the new device, investigators simply pour a smidgen of the suspect food
or drink directly into the ImmunoFlow鈥檚 testing chamber
(see Graphic). Solid
food has to be pulverised first with a bit of water or buffer solution. A
battery-operated pump pushes the sample into the testing chamber.
Inside the chamber are hundreds of glass beads, each coated with millions of
antibodies that stick to the kind of bacteria you are testing for, say
Salmonella. Previous antibody-based tests lacked the sensitivity of ImmunoFlow,
says Weimer, because they relied on the bacteria diffusing through a paper
membrane covered with antibodies. But bacteria are big and bulky, so they
diffuse slowly and incompletely, which makes the tests less sensitive. The pump
in the ImmunoFlow forces the liquid through the beads so the beads don鈥檛 get
clogged. The investigator then adds another set of antibodies labelled with a
luminescent marker that will bind to any antibody-bacterium complexes trapped in
the chamber, giving off a telltale glow.
You can鈥檛 spot the glow without plugging the ImmunoFlow into a small machine
called a photon counter. Right now, the photon counter is as big as a PC, but
Weimer鈥檚 new company, Biomatrix Solutions, is aiming to make smaller, portable
versions. He hopes to begin marketing ImmunoFlow next May.
Eventually, when the photon-reader is small enough,the gadget could be used
in the home to test meat or milk that has been sitting around in fridge for a
few days. 鈥淎 rapid test such as this could decrease the number of illnesses and
deaths due to food-borne bacteria,鈥� says Caroline Smith de Waal of the Center
for Science in the Public Interest, a nutrition and food safety advocacy group.
鈥淲e need to monitor food much more regularly than is being done today.鈥�