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Title: Effectiveness of Bacteriophages in Reducing Escherichia coli O157:H7 on Fresh Cut Cantaloupes and Lettuce

Author
item Sharma, Manan
item Patel, Jitu
item Conway, William
item Ferguson, Sean
item SULAKVELIDZE, ALEXANDER - INTRALYTIX, INC.

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/16/2009
Publication Date: 7/1/2009
Citation: Sharma, M., Patel, J.R., Conway, W.S., Ferguson, S.E., Sulakvelidze, A. 2009. Effectiveness of Bacteriophages in Reducing Escherichia coli O157:H7 on Fresh Cut Cantaloupes and Lettuce. Journal of Food Protection. 72(7):1481-1485.

Interpretive Summary: Bacteriophages are viruses that invade and lyse bacterial cells. Our work shows that bacteriophages specific for the bacterial pathogen E. coli O157:H7 were effective in reducing populations of the pathogen on lettuce and cantaloupe. On 9 cm^2 cut lettuce pieces, the spray application of 7.98 log PFU/cm^2 of bacteriophages (ECP-100) showed a significant reduction in E. coli O157:H7 counts compared to lettuce pieces treated with the control (phosphate buffered saline). Populations of E. coli O157:H7 on lettuce treated with ECP-100 on 0, 1, and 2 days (0.72, < 0.22, and 0.58 log CFU/cm^2 of lettuce) and stored at 4 deg C were significantly lower than those treated with control (2.64, 1.79, and 2.22 log CFU/cm^2), respectively. Populations of E. coli O157:H7 on cut cantaloupes treated with ECP-100 on days 2, 5, and 7 (0.77, 1.28, and 0.96 log CFU/ml) and stored at 4 deg C were significantly lower than those treated with control (3.34, 3.23, and 4.09 log CFU/ml), respectively. The effect of bacteriophages was apparent almost immediately after spray treatment in reducing E. coli O157:H7 on lettuce. This study is the first to show the effectiveness of a bacteriophage mixture to kill E. coli O157:H7 on fresh-cut lettuce and cantaloupes.

Technical Abstract: Outbreaks of foodborne illness have been associated with the consumption of cantaloupes and fresh-cut lettuce. Bacteriophage mixtures may be effective biocontrol agents to reduce E. coli O157:H7 on produce. The effectiveness of a mixture of bacteriophages (ECP-100) in reducing populations of E. coli O157:H7 on cut pieces of iceberg lettuce and cantaloupe was determined. E. coli O157:H7 gfp 86 was spot inoculated on lettuce pieces (9 cm^2) with 3.76 log CFU/cm^2, allowed to dry for 1 hr, and then sprayed with either control (phosphate buffered saline) or ECP-100 to deliver 7.98 log PFU/cm2 before being stored for either 0, 1, or 2 days at 4 deg C. Cut pieces of cantaloupe were spot inoculated with E. coli O157:H7 (4.55 log CFU/ml) and treated with control or ECP-100 (6.69 log PFU/ml), and then stored at 4 or 20 deg C for 0, 2, 5, or 7 days. On appropriate days, lettuce and cantaloupe samples were homogenized and populations of E. coli O157:H7 were enumerated on sorbitol MacConkey agar with ampicillin. Significant (P<0.05) effect of phage treatment on bacterial populations was determined. Populations of E. coli O157:H7 on lettuce treated with ECP-100 on 0, 1, and 2 days (0.72, < 0.22, and 0.58 log CFU/cm^2 of lettuce) and stored at 4 deg C were significantly lower than those treated with control (2.64, 1.79, and 2.22 log CFU/cm^2), respectively. Populations on cut cantaloupes treated with ECP-100 on days 2, 5, and 7 (0.77, 1.28, and 0.96 log CFU/ml) and stored at 4 deg C were significantly lower than those treated with control (3.34, 3.23, and 4.09 log CFU/ml), respectively. The bacteriophage treatment reduced populations of E. coli O157:H7 immediately upon application to lettuce. This study is the first to show the effectiveness of a bacteriophage mixture to kill E. coli O157:H7 on fresh-cut lettuce and cantaloupes.