Purpose: Identify microbiological reservoirs and dissemination routes contributing to the microbiological quality of in-field leafy greens.
Methods: Pre-harvest plant (n=423) and environmental samples (irrigation water, harvesting equipment, hand swabs, soil; n=107) were collected from an organic production system in BC weekly between August and October 2011. Levels of coliforms and Escherichia coli were determined using 3M Petri-Films. Enterococcus spp. were detected using Enterococcosel enrichment broth and agar. Recovered E. coliisolates were subjected to antibiogram and multiplex PCR–based phylogenetic typing.
Results: Coliform levels on in-field leafy greens ranged from 0.7 to 1.8 log CFU/g (average; 1.1 ± 0.1 log CFU/g). The overall prevalence of E. coli recovered from leafy greens was 1.7%. Generic E. coli were recovered repeatedly from the irrigation water reservoir (32%), overhead sprinkler (67%), soil (43%), and worker hand swabs (15%). E. coliisolates belonging to all four phylogroups (A, B1, B2, D) were detected in the irrigation reservoir well, whilst only B1 isolates were recovered from the sprinkler. Workers’ hands showed the presence of isolates belonging to A and D, and soil samples revealed the presence of B1 and D phylogroups. Common to isolates recovered from identified reservoirs and isolates on leafy greens were phylogroups A, B1 and B2, suggesting possible dissemination.
Significance: Overall, although numerous E. coli reservoirs were identified on-farm, levels of coliforms and E. coli recovered from in-field leafy greens were low. Despite this, phylogrouping data highlight possible transmission routes and the consequent need to develop intervention strategies that disconnect potential contamination routes from the farm environment to produce.