A joint team of U.S. and Taiwanese scientists has created a fast and efficient method to catch listeria-contaminated food using a modified blood glucose monitor of the kind used by thousands of diabetic patients worldwide.

More than 180,000 melons were recalled in the United States during 2011, after infected melons caused the death 33 people with the food-borne, intestinal bacteria Listeria monocytogenes. It was the worst outbreak, measured in number of deaths, since the Center for Disease Control and Prevention began tracking outbreaks of listeria in the 1970s. By the time the case was resolved, 147 people across 28 states were infected by five different subtypes of listeria traced to a cantaloupe farm in Colorado.

According to the U.S. Food and Drug Administration, it takes five to seven days in the lab using traditional methods to detect L. monocytogenes, a long enough window of opportunity for the contaminated food source to be widely distributed, for the bacteria to spread, for many more people to be infected, and ultimately for a few more deaths to occur. Considering the global nature of our food supply and distribution, a rapid, field-based detector for listeria has the potential to greatly impact the reduction of global health risks from this often deadly infection.

The scientists’ key innovations are a modified biosensor strip and a detection electrode with gold nanoparticles. The modified strip is dabbed with food samples just as people with diabetes dab blood on the traditional strip.

The scientists adapted the carbon electrode strips used by diabetics for glucose monitoring by immobilizing gold nanoparticles and specific antibodies directed against listeria on the strip, to create an immune-biosensing strip. To alleviate the need for growing sufficient bacteria for traditional, time consuming lab-based tests, the scientists used standard microscopy techniques that amplify the detection of low numbers of proteins or cells, and incorporated those techniques directly onto the strips.

The strip is placed in a holder with a modified electrode, the team’s second innovation. The scientists modified the standard electrode used for glucose detection by again incorporating gold nanoparticles, which are known for their biological compatibility, ability to amplify signals, and conducting capability. The amount of detected listeria on the strip is reported to a PalmSense device and hand-held PDA for graphical presentation in the same manner as glucose in a blood sample is reported.

“Nanoscale science continues to play a major role in catalyzing biotechnology innovation, yielding a broad spectrum of devices and products that are addressing many pressing social needs,” says Larry Walker, professor, Biological & Environmental Engineering, Cornell University. He is co-editor-in-chief of Industrial Biotechnology, the journal that published the paper.

The team consisted of scientists from the Taiwanese company Apex Biotechnology, founded in 1997 and the first publicly listed biotechnology company in Taiwan; National Chiao Tung University, Taiwan; The University of Maine; and a student from Bangor High School, Maine.

The nanotechnology-based method is highly specific for listeria and has the potential for low-cost commercial development. It can detect the bacteria at minute amounts, is specific for listeria over other intestinal disease-causing pathogens such as the deadly Escherichia coli strain O157:H7 and Salmonella Typhimurium, and results can be obtained in hours. The traditional detection method for listeria is labor intensive and takes days to complete, requiring 24 to 48 hours to grow enough of the bacteria sufficient for testing, followed by plating the bacteria on a special type of agar that fosters selective growth of the bacteria, and then confirmatory tests.

Listeriosis sickens 2,500 people in the U.S. each year and many more worldwide, killing about 25 to 30 percent of those infected. The risk of bacterial contamination can be reduced by safe food preparation, safe consumption, and proper storage conditions.