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Eurofins Unveils Multiplexed DNA Chip-based Testing Service to Detect Unwanted Animal DNA in Food and Feed

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NEW YORK (GenomeWeb) – A new DNA testing service could help address concerns raised by the European horse meat crisis of 2013, when regulators found that European beef contained large amounts of horsemeat.

Luxembourg-based Eurofins has developed a new testing service to address problems with adulterated meat. Based on DNA chip technology and able to detect up to 21 species from a single sample, the test uses consensus PCR of mitochondrial DNA (mtDNA) and hybridization arrays to miniaturize and multiplex the detection of extraneous species.

After the horsemeat scandal, where some beef products contained 100 percent horsemeat, companies started to test their meat to verify its animal of origin, Adreas Pardigol, scientific director of molecular biology at Eurofins Analytics, told GenomeWeb. But the available PCR-based tests were only capable of detecting one species.

"One test for one species, so if you just ran a beef PCR test, you had no information whether there is something else than beef," he said.

Companies often wanted to check products that contained several kinds of meat, or test for one or more potential contaminants, requiring multiple tests that drove the price higher with each additional species. "There was a need to develop a test which is capable of detecting all these required species, for a low price," he said.

Eurofins addressed this by creating a testing service based on commercially available meat testing DNA chip kits from German LCD-array firm Chipron. Pardigol said that the firm has added its expertise in sample preparation and DNA extraction to optimize and validate the process for each of the 21 kinds of meat, including beef, horse, pork, chicken, and duck.

Chipron provides the biochip as a ready-to-use unit, like a consumable, Pardigol explained. The chip surface is about the size of a postage stamp and features species-specific hybridization probes immobilized on its surface. DNA from each species will bind to a specific location on the chip.

The test analyzes mtDNA, an optimal target because there is one gene that has the power to both detect and differentiate all the necessary species, Pardigol said. Consensus PCR can amplify the DNA from all the species, while the hybridization probes can detect each species separately.

Pardigol compared the chemistry to an ELISA test, just in miniaturized form. "It uses principles applied to ELISA technologies," he said.

To provide a result for each species, a chip scanner looks for a precipitation signal based on an enzymatic reaction at specific locations on the chip surface. Each species binds to a different location and specialized software will register a positive or negative signal.

Testing is performed as a service at Eurofins' molecular biology testing unit in Nantes, France. Turnaround time is approximately five days, and the list price for one sample tested is €150 ($168). The customer can specify whether it wants to test for all 21 of the available species, or just a few. Savings compared to species-by-species testing come partly from reduced labor and reagent costs, Pardigol said.

Pardigol stressed that Eurofins had not developed new technology, but rather optimized and validated the process to provide reliable, sensitive, and specific results.

"You can have the best biochip technology in the world, but if you have bad preparation of your sample then you have no reliable result," he said. "Fifty percent of the performance of the method is based on things you cannot buy, because it's a process and the process is lab specific."

The process is not completely automated, so it requires skilled technicians and dedicated labs with physical separation of the different parts of the analysis, he said. Samples can become contaminated without physical separation, which he said Eurofins had already established in its laboratory.

"The thing we have done here is mostly validation. It starts with sample prep and DNA extraction. That's what we optimized for this test," said Pardigol. "What is new is miniaturization of amplification and detection."

He explained that there is no international standard or norm for animal identification tests in food. "It's an internal standard that we've set up here," he said. The chips come pre-loaded with probes to detect the 21 species, but Eurofins ran experiments to validate each of them using reference DNA from other sources.

Still, Pardigol said Eurofins brought in Cofrac, the French accreditation committee, to audit the testing process on site. Through Cofrac, the firm received ISO 17025 accreditation for the animal identification service on June 1.

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