Phage 'cocktail' wipes out 99% of E. coli in spinach
An injection of bacteriophages - also known informally as "phages" - nearly eradicated a toxin-producing strain of E. coli in contaminated spinach and other products, 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 food borne pathogens," Ebner said. "Applying this kind of therapy to contaminated foods will make them safer."
While most strains of E. coli are harmless, some can cause severe and potentially fatal illnesses. The strain used in Ebner's study - E. coli O157:H7 - caused more than 63,000 illnesses, 2,100 hospitalizations and 20 deaths in the U.S. in 2011. Ingesting as few as 10 colony-forming units of E. coli O157:H7 can result in serious illness.
Most E. coli infections are caused by eating undercooked meat contaminated with the bacteria, but outbreaks associated with fresh produce such as spinach are on the rise.
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. E. coli dropped by more than 99.8 percent and about 99.8 percent in spinach after 48 and 72 hours, respectively.
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