Spinach scare highlights need for inline food testing


By James R. Dukart

A molecular diagnostic tool has been at the forefront of addressing the recent outbreak of E. coli detected in fresh spinach, which had resulted in nearly 200 cases of illness as of late September. The experience is motivating toolmakers to hone their abilities to prevent food safety problems in the future.

A government lab used a system manufactured by Sunnyvale, Calif.-based Cepheid to isolate the E. coli earlier this year. Using the system, researchers performed rapid molecular tests that pointed to a bag of spinach that sickened a New Mexico woman. While the technology provided a critical breakthrough in the case, Cepheid’s chief medical and technology officer, David Persing, says the goal must be to detect and intercept pathogens long before they enter the general food supply.

“We need to identify the source much earlier in the process, some way of testing foodstuffs coming out of a particular farm or on a lot-specific basis,” Persing says. “In this case, it may have been one truckload of spinach that was contaminated, and that single load knocked out so many others because we did not know exactly where it was.”

Persing envisions greater public awareness of food safety, perhaps including certification programs for bags of fresh produce. He likens it to the response to the anthrax scare at the post office. Cepheid works with Northrop Grumman and others to apply its technology at hundreds of U.S. Post Office branches throughout the country, and offers a range of sensors and diagnostic products aimed at testing for pathogens from anthrax to salmonella. Persing sees similar deployment of sensor technology for agricultural operations, food distribution centers and perhaps even grocery stores.

The company is not the only one pursuing the opportunity. Santa Clara, Calif.-based NanoSensors is licensing nanoporous silicon-based biosensor technology through Michigan State University and a university in Korea to develop food safety analysis systems. In addition to silicon-based filters, NanoSensors is also using carbon nanotube technology to detect and isolate biologically-based pathogens.

A government lab isolated E. coli from a bag of spinach that sickened a New Mexico woman by performing a rapid molecular diagnostic test with Cepheid’s SmartCycler instrument, shown here. Unlike traditional culture tests that take days to generate a result, molecular diagnostics quickly and accurately identify microorganisms by identifying specific segments of DNA. Photo courtesy of Cepheid
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“This is a market that is ripe for a solution,” says Joshua Moser, vice president and chief operating officer of NanoSensors. “Food safety may not be as sexy as testing for anthrax or liquid explosives in airports, but it’s a problem. We need to find a solution.”

Nano- or molecular-scaled devices operate at the same scale as the biological agents they target, he explained, allowing the technology to both detect and isolate targeted pathogens. Nanoprobes and filters can address viruses and bacteria at a level of specificity hard to get at with larger, more unwieldy technology, while at the same time promising faster, more accurate results than existing technology.

Another advantage to molecular detection, Persing adds, is that it works in ways contemporary culture-based technologies fall short. “The viability of the bacteria might go down over time,” he says. “It gets degraded, but that is where the molecular techniques really shine, since they can detect DNA whether alive or dead.”

Both Persing and Moser expect the movement of food-testing technology from research labs to the field to be expedited in light of recent events.

“We’re seeing a lot of attention paid to this now,” Moser says, “and not just because we are in California, which is such a large food producer.”

NanoSensors is working on a reusable testing kit - a disposable sensor that reports back to an external data acquisition unit - that can be used by people at all levels of the food distribution chain, from farmers to wholesalers to retail grocers. Moser refers to the product as a “razor
azorblade” model, where customers will buy and use disposable sensors on each specific lot of produce that is tested. He also sees government agencies pushing for stronger testing in the wake of the E. coli spinach outbreak.

“Situations like this cannot help but raise consciousness,” says Cepheid’s Persing. “The connection has already been proven by molecular testing. In addition to illness and loss of life, any significant outbreak of one of nature’s biothreats results in tremendous economic loss as well.”