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United States Department of Agriculture

Agricultural Research Service

Research Project: MICROBIAL ECOLOGY AND SAFETY OF FRESH PRODUCE

Location: Environmental Microbial and Food Safety Laboratory

Title: Biocontrol of Escherichia coli O157:H7 on fresh-cut spinach and lettuce using a bacteriophage cocktail

Authors
item Boyacioglu, Olcay -
item Sharma, Manan
item Sulakvelidze, Alexander -
item Goktepe, Ipek -

Submitted to: Bacteriophage
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 9, 2013
Publication Date: April 9, 2013
Citation: Boyacioglu, O., Sharma, M., Sulakvelidze, A., Goktepe, I. 2013. Biocontrol of Escherichia coli O157:H7 on fresh-cut spinach and lettuce using a bacteriophage cocktail. Bacteriophage. DOI: 10.4161/bact.24620.

Interpretive Summary: Viruses which can infect and kill bacterial cells are known as bacteriophages (phages). The application of bacteriophages to fresh cut leafy greens can help reduce enteric pathogenic bacterial populations on these commodities. This study evaluated the use of phages against several strains of the pathogen E. coli O157:H7 and examined how quickly the bacteriophages can be effective. The results presented here indicate that when sprayed on to lettuce and spinach, phages can begin to reduce E. coli O157:H7 populations within 30 min of application when stored under standard refrigeration temperatures. This information should be useful to other scientists and the produce industry.

Technical Abstract: The effect of an E. coli O157:H7-specific bacteriophage cocktail (EcoShield™) was evaluated against nalidixic acid resistant (NalR) E. coli O157:H7 strains in either a) laboratory medium or b) on leafy greens. Laboratory medium cultures were inoculated with 5 log CFU/ml and treated with 7 log PFU/ml phage cocktail. Pieces (~2x2 cm2) of leafy greens (lettuce and spinach) inoculated with 4.5 log CFU/cm2 were sprayed with EcoShield (6.5 log PFU/cm2). Samples were stored at 4 or 10°C for up to 7 days. Results showed that the E. coli O157:H7-specific phage cocktail reduced bacterial populations by an average of 4.5 log CFU/ml in TSB at 4°C (p < 0.05). On spinach, the level of E. coli O157:H7 RM4407 NalR declined by 2.38 and 2.49 log CFU/cm2 at 4 and 10°C, respectively, 30 min after phage introduction (p < 0.05). EcoShield was also effective in reducing the E. coli O157:H7 on the surface of green leaf lettuce stored at 4°C by 2.49 and 3.28 log units in 30 min and 2 h, respectively (p < 0.05). Overall, these results suggest that EcoShield may be used successfully in effectively reducing E. coli O157:H7 populations on fresh produce stored at 4°C.

Last Modified: 8/27/2014
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