Viral bacteria engineered to spot E. coli

By Don Schrack

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(Oct. 2, 11:40 a.m.) Intelliphage, West Lafayette, Ind., has developed what could be a breakthrough in the ongoing food safety campaign.

“The beauty of this system is we believe it’s going to be very cheap,” said Bruce Applegate, a founder of Intelliphage and an associate professor at Purdue University’s Department of Food Sciences.

Applegate and his research staff modified an existing bacterial virus — or phage — specific to E. coli 15787. When the E. coli is present, the phage turns bright red.

“The phage will actually bind to the bacteria, which is usually irreversible, and inject their DNA into the bacteria,” Applegate said. “That will cause the bacteria to make more phage.”

When the phage attaches to the E. coli, the color change can become apparent within four hours, Applegate said. Other applications can take 24 hours or longer, he said. The Intelliphage product is not yet available for commercial application.

“Right now, we’re a just startup company, so we’re looking for money,” Applegate said. “But it could go very, very quickly, because it’s not going to take a lot of money.”

Commercial packinghouses that use the Intelliphage technology will require little or no investment, Applegate said.

Most food companies already have the equipment needed to detect the luminescent bacteria, he said.

The Intelliphage technology permits the recovery of the bacteria, which Applegate said is critical in the event of a recall when a food company is trying to track a contaminant to its source.

Other Intelliphage products that target other bacteria may soon follow the E. coli technology.

“Because we know so much about this phage, we can just change its specificity to go after salmonella or other strains,” Applegate said. “Phage detection has been around for a while, but it’s as if no one has bothered to take it to practical application.”

An Intelliphage product that detects listeria is being prepared for license, Applegate said.

Because the bioluminescent phage is grown in bacteria, the big hurdle in producing large quantities, he said, is the danger of having substantial amounts of E. coli in the laboratory and the potential for accidental release. Intelliphage has cleared that hurdle.

“We’ve actually figured out a way to grow this phage in an E. coli host that is commonly used in laboratories and is not pathogenic,” Applegate said.

In the past, Applegate said, the problem with using phage to detect and concentrate bacteria was the bacteria would develop resistant strains. He likened the problem to a physician’s using antibiotics to treat patients over a long period of time.

“Because we’ve genetically engineered the phage, we can control the conditions,” he said.

While the Intelliphage products may speed detection of bacteria in commercial packing operations, their use may be as valuable in even the poorest of countries.

“We’re looking at it in terms of … countries where there may be no electricity,” Applegate said. “As long as the bacteria are growing and there are enough available, you’re going to see it.”



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