Officials from the New Jersey Department of Health said yesterday that an E. coli outbreak has spread to four New Jersey counties. Six cases have been reported in Hunterdon, Middlesex, Somerset, and Warren counties.

Separately, a team of biochemists and mechanical and chemical engineers at McMaster University says it has developed a transparent test patch that can signal food contamination as it happens. The patch can be incorporated directly into food packaging, where it can monitor the contents for harmful pathogens such as E. coli and Salmonella.

The researchers point out that the same technology could also be used in other applications, such as bandages to indicate if wounds are infected, or for wrapping surgical instruments to assure they are sterile.

The study (“Sentinel Wraps: Real-Time Monitoring of Food Contamination by Printing DNAzyme Probes on Food Packaging”) that describes the new technology is published in ACS Nano. The team believes it has the potential to replace the traditional “best before” date on food and drinks alike with a definitive indication that it's time to get rid of a roast or pour out a carton of milk.

“Here, we report the development of a transparent, durable, and flexible sensing surface that generates a fluorescence signal in the presence of a specific target bacterium. This material can be used in packaging, and it is capable of monitoring microbial contamination in various types of food products in real time without having to remove the sample or the sensor from the package. The sensor was fabricated by covalently attaching picoliter-sized microarrays of an E. coli-specific RNA-cleaving fluorogenic DNAzyme probe (RFD-EC1) to a thin, flexible, and transparent cyclo-olefin polymer (COP) film,” write the investigators.

McMaster researchers have developed a test to identify whether meat and other foods are safe to eat or need to be thrown out.

“Our experimental results demonstrate that the developed (RFD-EC1)-COP surface is specific, stable for at least 14 days under various pH conditions (pH 3–9), and can detect E. coli in meat and apple juice at concentrations as low as 103 CFU/mL. Furthermore, we demonstrate that our sensor is capable of detecting bacteria while still attached to the food package, which eliminates the need to manipulate the sample. The developed biosensors are stable for at least the shelf life of perishable packaged food products and provide a packaging solution for real-time monitoring of pathogens. These sensors hold the potential to make a significant contribution to the ongoing efforts to mitigate the negative public-health-related impacts of foodborne illnesses.”

“In the future, if you go to a store and you want to be sure the meat you're buying is safe at any point before you use it, you'll have a much more reliable way than the expiration date,” says lead author Hanie Yousefi, a graduate student and research assistant in McMaster's Faculty of Engineering.

If a pathogen is present in the food or drink inside the package, it would trigger a signal in the packaging that could be read by a smartphone or other simple device. The test itself does not affect the contents of the package.

According to the World Health Organization, foodborne pathogens result in approximately 600 million illnesses and 420,000 deaths per year. About 30 percent of those cases involve children five years old and younger. 

The researchers have named the new material “Sentinel Wrap” in tribute to the McMaster-based Sentinel Bioactive Paper Network, an interdisciplinary research network that worked on paper-based detection systems. That network's research ultimately gave rise to the new food-testing technology.

The signaling technology for the food test was developed in the McMaster labs of biochemist Yingfu Li, Ph.D. “He created the key, and we have built a lock and a door to go with it,” says Carlos Filipe, Ph.D., chair of McMaster's Department of Chemical Engineering.

Mass producing such a patch would be fairly cheap and simple, the researchers say, as the DNA molecules that detect food pathogens can be printed onto the test material.

“A food manufacturer could easily incorporate this into its production process,” says Tohid Didar, Ph.D., an assistant professor of mechanical engineering and member of the McMaster Institute for Infectious Disease Research.

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