Wednesday, July 31, 2013
Exhibit Hall (Charlotte Convention Center)
Jayde Wood, University of British Columbia, Vancouver, Canada
Elsie Friesen, BC MAL, Abbotsford, Canada
Pascal Delaquis, Agriculture and Agri-Food Canada, Summerland, Canada
Kevin Allen, University of British Columbia, Vancouver, Canada
Introduction: There is interest in developing more effective on-farm food safety interventions to reduce risks associated with fresh produce. Specifically, irrigation water and compost are significant concerns regarding the transmission of pathogenic organisms to in-field produce.
Purpose: To determine whether populations of Escherichia coli recovered from compost and irrigation water are observed in soil and in-field leafy greens.
Methods: In-field leafy greens (n=484) and environmental samples (irrigation water, compost and soil; n = 136) were collected from two produce production systems (organic and conventional) in British Columbia weekly (July-October 2012). Coliforms and Escherichia coli counts were determined using 3M Petri-film and E. coli prevalence was evaluated by enrichment using EC broth and EMB agar. Escherichia coli isolates were subjected to BOX-PCR and multiplex PCR phylogenetic typing.
Results: Coliform and E. coli levels on leafy greens ranged from 0.7 to 4.5 log CFU/g (mean: 1.2 ± 0.1 log CFU/g) and 0.7 to 1.6 log CFU/g (mean: 0.7 ± 0.005 log CFU/g), respectively. The overall prevalence of E. coli for leafy greens was 0.7%. Escherichia coli were recovered from the irrigation water reservoir (54%), overhead sprinkler (26%), soil (32%), and compost (6%) samples. Escherichia coli isolates belonging to four phylogenetic groups (A, B1, B2, D) were recovered from both produce production systems, with B1 being the pre-dominant phylogroup (78%). BOX-PCR revealed identical fingerprints for E. coli isolates recovered from irrigation water and in-field plants, demonstrating dissemination from the reservoir to the field. Similarly, identical strains from compost were also recovered on leafy greens.
Significance: Levels of coliforms and E. coli recovered from in-field leafy greens were low. Despite this, BOX-PCR data highlight transmission routes and the consequent need to develop intervention strategies minimizing the transfer of potential pathogens from compost and irrigation water to in-field leafy greens.
