Phage 'cocktail' wipes out E. coli

Phage 'cocktail' wipes out E. coli

TREATING food products with select bacteriophages — viruses that target and kill bacteria — could significantly reduce concentrations of Escherichia coli, according to a Purdue University study.

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%.

The study suggests that phage treatment could be an effective tool to help ensure the safety of food products, said Paul Ebner, Purdue 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 O157:H7, 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%. E. coli levels dropped by more than 99.8% and about 99.8% in spinach after 48 and 72 hours, respectively.

In ground beef stored at room temperature, the phages cleaned up about 99% of E. coli bacteria within 24 hours. The amount of E. coli in refrigerated and undercooked ground beef dropped by about 68% and 73%, respectively.

"Bacteria have viruses just like we do," Ebner said. "We're taking what already exists in nature and concentrating it to have an impact on these bacteria."

Ingesting phages does not pose a threat to human health because phages are highly host-specific, targeting only certain types of bacteria, Ebner said.

"Phage therapy is a way of using microbes beneficially, similar to using probiotics in yogurt," he said.

Interest in using phages as an antibacterial treatment has increased with the rise of antibiotic-resistant bacteria. The host specificity of phages can be an advantage over broad-spectrum antibiotics, which can wipe out both pathogenic and beneficial bacteria, Ebner noted.

He said phage therapy is not a substitute for antibiotics, but "it can be very effective when used at specific time points and for shorter periods."

The paper was published in the Journal of Animal Science.

Volume:86 Issue:15

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