Phage cocktail wipes out 99 percent of E. coli in meat, spinach

Treating food products with select bacteriophages - viruses that target and kill bacteria - could significantly reduce concentrations of E. coli, a Purdue University study shows.

An injection of bacteriophages - also known informally as "phages" - nearly eradicated a toxin-producing strain of E. coli in contaminated spinach and ground beef, in some cases decreasing E. coli concentrations by about 99 percent.

The study suggests that bacteriophage treatment could be an effective tool to help ensure the safety of food products, said Paul Ebner, associate professor of animal sciences.

"Phage treatment is a way of harnessing the natural antibacterial properties of phages to limit E. coli and other important foodborne pathogens," Ebner said. "Applying this kind of therapy to contaminated foods will make them safer."

Ebner and Purdue graduate students Yingying Hong and Yanying Pan infected fresh spinach leaves and ground beef with about 10 million cells of E. coli, a far greater amount than typically found in contaminated food products, Ebner said. The researchers then treated the food with a "phage cocktail," a liquid containing three kinds of phages selected for their ability to quickly and efficiently kill E. coli. Using a variety of phages also helps prevent the bacteria from developing resistance.

After 24 hours, the treatment had reduced E. coli concentrations in the spinach, stored at room temperature, by more than 99.9 percent. In ground beef stored at room temperature, the phages cleaned up about 99 percent of E. coli bacteria within 24 hours. The number of E. coli in refrigerated and undercooked ground beef shrunk by about 68 percent and 73 percent, respectively.