By Lee Anna Sherman
The news grabbed national headlines in early 2009: eight dead, hundreds sickened by food poisoning in 34 states. After investigators traced the outbreak to Salmonella-tainted peanut butter from a Georgia plant, stores pulled thousands of products from their shelves. Worried consumers tossed suspect items into the trash. At least 100 companies will post losses from the episode, warned the Food Liability Law Blog in February.
Clearly, contaminated foods must be destroyed. But every year, thousands of perfectly safe products can end up in the waste bin for lack of onsite testing technologies that are easy, reliable and directly assess microbial toxicity. A 2006 E. coli outbreak (strain O157:H7) cost California spinach farmers $74 million. In 2008, tons of tomatoes were dumped during a Salmonella outbreak before the real culprit — a Mexican jalapeno pepper — was identified. Cost to growers: an estimated $450 million.
Until now, there’s been no quick, accurate way to directly test food products for bacterial toxicity. But a major breakthrough in the laboratory of OSU microbiologist Janine Trempy promises to help limit food-borne illnesses and spare lives while potentially saving companies millions in unnecessary recalls.
This very big discovery turned up in cells of a very small fish.
Trempy discovered that the pigment cells of the Siamese fighting fish, Betta splendens, act as a natural alarm — a “biosensor” — signaling the presence of toxin-producing bacteria that contaminate food or drinking water. Scientists had observed that the brilliantly hued fish gets lighter in color when stressed or exposed to toxic chemicals such as mercury. Trempy and her team of students observed the same color-change reaction when they exposed the fish’s red pigment cells, called erythrophores, to toxin-producing bacteria such as Salmonella, Bacillus cereus and Clostridium botulinum (which causes botulism and has potential for use as a biological weapon).
“We discovered that the red pigment cells respond immediately to certain food-associated, toxin-producing bacteria responsible for making humans sick,” explains Trempy, associate dean of the OSU College of Science. “This response to bacterial toxicity can be easily seen under a low-power microscope and quickly quantified, numerically, to describe the intensity of the situation.”
The discovery’s potential was immediately clear. Food inspectors, grocers, manufacturers, farmers, even consumers, could test food for safety right at the farm, the factory, the retail outlet and the home kitchen. Recalls could be done more strategically, pulling only foods that are proven dangerous rather than sweeping away everything with a “better-safe-than-sorry” approach.
Current detection technologies are simply too limited to be widely effective, Trempy explains in a recent paper in Microbial Biotechnology. Typically based on DNA or protein analysis, these technologies are unable to distinguish between live and dead bacteria, she says. Nor can they directly assess the degree of toxicity of the offending bacteria. They cannot recognize new or emerging strains of bacteria. And there are challenges of speed and logistics, she notes.
“These challenges often include time-intensive sampling and testing practices, long culture times to increase the number of bacteria to detectable levels, and costly shipment methods to move samples to a central laboratory for additional analysis to verify toxicity once a specific bacterium is detected,” she says.
With the biosensor technology newly patented, Trempy is moving toward commercialization with a team of researchers at Cornell University. They are working to devise a portable, easy-to-use testing kit using advanced optics and software for image capture and interpretation — what she calls “futuristic hardware.” She envisions a time in the not-too-distant future when food processors, distributors, handlers and even everyday consumers can find out instantly whether food is safe to eat.
Watch a video produced January 22, 2009 by Discovery Canada about the Siamese fighting fish and the new biosensor.
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