Application of lytic phages to lettuce to reduce E. coli O157:H7

What is it about?

LLytic bacteriophages (phages), viruses which have the ability to kill pathogenic foodborne bacteria, were evaluated for the ability to prevent cross contamination of fresh-cut lettuce with E. coli O157:H7 that could be present in the washwater. Lettuce was first treated with the phages and then exposed to E. coli O157:H7, an enteric foodborne pathogen which contaminated various produce commodities (lettuce, spinach, sprouts, hazelnuts) in recent years. Lettuce was treated with the phages in different manners (immersion or spray) and then stored for a period of time a refrigerated temperature. The results presented here indicate that the manner and amount of phages applied to the lettuce influence how much E. coli O157:H7 can be reduced on the fresh cut lettuce surface. This work is a preliminary indication that exposure of lettuce to lytic bacteriophages may reduce E. coli O157:H7 populations on fresh cut lettuce stored at refrigeration temperatures.

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Why is it important?

This work shows that spraying lytic phages specific for E. coli O157:H7 on to lettuce is more effective than immersing the lettuce in a phage suspenstion. This work also shows that sodium hypochlorite does not inactivate the phages and could potentially be used in combination with a phage-based treatment to inactivate E. coli O157:H7 on fresh cut lettuce.