MICROBIAL ECOLOGY AND SAFETY OF FRESH ON-FARM ORGANICALLY GROWN PRODUCE
Title: Biocontrol of Escherichia coli O157:H7 on fresh-cut lettuce and cantaloupe by treatment with bacteriophage
Submitted to: International Association for Food Protection Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: March 5, 2008
Publication Date: August 3, 2008
Citation: Sharma, M., Patel, J.R., Conway, W.S., Ferguson, S., Sulakvelidze, A. 2008. Biocontrol of Escherichia coli O157:H7 on fresh-cut lettuce and cantaloupe by treatment with bacteriophage [abstract]. International Association for Food Protection 2008 Abstract Book. Paper No. P5-25. p. 160.
Introduction: 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.
Purpose: 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.
Methods: 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 control (phosphate buffered saline) or ECP-100 to deliver 7.98 log PFU/ cm^2 before being stored for 0, 1, or 2 days at 4 C. Fresh 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 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, if any, was determined.
Results: 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/cm2 of lettuce) and stored at 4 C were significantly lower than those treated with control (2.64, 1.79, and 2.22 log CFU/cm2), 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 C were significantly lower than those treated with control (3.34, 3.23, and 4.09 log CFU/ml), respectively.
Significance: The bacteriophage treatment reduced populations of E. coli O157:H7 immediately upon application to lettuce. This study is the first to shows the effectiveness of a bacteriophage mixture to kill E. coli O157:H7 on fresh-cut lettuce and cantaloupes.