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Photo: A computer and camera system which detects the foodborne toxin Shiga. Link to photo information
ARS scientists have developed a new low-cost way to test foods for the Shiga toxin, a product of Escherichia coli O157:H7. Click the image for more information about it.

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Food Toxin Detector Incorporates Camera

By Sandra Avant
September 29, 2015

A new system that incorporates a digital camera to detect pathogens that cause foodborne illness has been developed by U.S. Department of Agriculture (USDA) scientists.

The high cost of equipment used to identify pathogens restricts widespread testing of foods for toxins that cause food poisoning, which sickens millions of Americans each year. The new system, devised by chemist Reuven Rasooly and his colleagues at the Agricultural Research Service's Western Regional Research Center (WRRC) in Albany, California, measures Shiga toxin activity as effectively as equipment that costs 100 times more.

Shiga toxin, a product of Escherichia coli (E. coli) O157:H7, is a major concern for the food industry. It is estimated that E. coli O157:H7 causes 73,000 cases of food poisoning and more than 60 deaths in the United States each year. It is critical to be able to determine toxin activity, because the active form poses a threat to humans, and the inactive form is nontoxic. However, current immunological tests cannot distinguish between the active and inactive form of Shiga toxin.

The new inexpensive system can distinguish between active and inactive toxins, according to Rasooly. It involves a $300 camera and a light-emitting source to biologically determine active toxin. A fluorometer, which is generally used to detect toxins, costs about $35,000.

Research on this project involved constructing a fluorescence detection system using a camera and light source to measure toxicity in a Shiga toxin food sample. Fluorescence measurements were obtained by taking a picture with a camera and analyzing the image with a free, available computer software.

The system is easy to adapt and also can be used to detect other foodborne toxins. When compared with a commercial fluorometer for detecting active Shiga toxin, both methods had the same toxin detection level.

This type of technology is a big plus, especially for developing countries where the risk of foodborne illness and outbreaks is greater. It is easy and affordable for diagnostic laboratories that cannot afford a fluorometer to detect food toxins.

ARS is USDA's principal intramural scientific research agency.

Read more about this work in the September 2015 issue of AgResearch.