Fate of Escherichia coli O157:H7 in field-inoculated lettuce |
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Authors: | Moyne Anne-Laure Sudarshana Mysore R Blessington Tyann Koike Steven T Cahn Michael D Harris Linda J |
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Affiliation: | aDepartment of Food Science and Technology, University of California, One Shields Ave., Davis, CA 95616-8598, USA;bWestern Institute for Food Safety and Security, University of California, One Shields Ave., Davis, CA 95616-8598, USA;cUniversity of California Cooperative Extension, 1432 Abbott Street, Salinas, CA 93901, USA |
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Abstract: | Impact of drip and overhead sprinkler irrigation on the persistence of attenuated Escherichia coli O157:H7 in the lettuce phyllosphere was investigated using a split-plot design in four field trials conducted in the Salinas Valley, California, between summer 2007 and fall 2009. Rifampicin-resistant attenuated E. coli O157:H7 ATCC 700728 (BLS1) was inoculated onto the soil beds after seeding with a backpack sprayer or onto 2- or 4-week-old lettuce plant foliage with a spray bottle at a level of 7 log CFU ml−1. When E. coli O157:H7 was inoculated onto 2-week-old plants, the organism was recovered by enrichment in 1 of 120 or 0 of 240 plants at 21 or 28 days post-inoculation, respectively. For the four trials where inoculum was applied to 4-week-old plants, the population size of E. coli O157:H7 declined rapidly and by day 7, counts were near or below the limit of detection (10 cells per plant) for 82% or more of the samples. However, in 3 out 4 field trials E. coli O157:H7 was still detected in lettuce plants by enrichment 4-weeks post-inoculation. Neither drip nor overhead sprinkler irrigation consistently influenced the survival of E. coli O157:H7 on lettuce. |
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Keywords: | Lettuce E. coli O157:H7 Field Irrigation |
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