Each year, contamination by E. coli bacteria causes more than 70,000 cases of food poisoning. Present methods for detecting these germs in food entail making bacterial cultures and take eight to 48 hours to deliver a verdict. A fiber-optic probe originally intended for sniffing out biowarfare agents works in as little as 15 minutes, says microbiologist Daniel DeMarco at the University of South Florida.
The probe consists of an optical fiber whose tip is coated with antibodies that pick up bacteria in the food being tested. Researchers then add fluorescently tagged antibodies to the sample. These labeled antibodies stick to the bacteria on the probe. A laser pulse sent down the probe triggers fluorescent emissions that travel back up the fiber when bacteria are present. The probe, developed by Research International in Woodinville, Wash., and the Naval Research Laboratory, is three to four times more sensitive than other detection systems, DeMarco says. He has tested the instrument on ground beef and apple cider and is adapting it to sense Listeria and Salmonella, two other common food poisons.