Examination of microbiological quality of in-field leafy vegetables and identification of on-farm generic Escherichia coli transmission dynamics
department or school: Land and Food Systems, Faculty of
data provider: DSpace
degree campus: UBCV
creator: Wood, Jayde Lian
issued: 2013-06-28T09:15:08Z
issued: 2013
related degree: Master of Science - MSc
degree grantor: University of British Columbia
description: Fresh produce has increasingly been linked to foodborne outbreaks in North America. Although contamination of produce may occur at any point along the food continuum, significant risks are thought to occur at the farm level. Data illustrating bacterial transmission dynamics on farm, however, are lacking. The aim of this project was to produce baseline data describing the occurrence of indicator bacteria on in-field leafy vegetables; examine antimicrobial resistance (AMR) of recovered Escherichia coli; and identify on-farm microbiological reservoirs impacting leafy vegetables. In-field plants (n=1093) and environmental samples (irrigation water, compost, soil, and hand swabs; n=316) were collected from two production systems (conventional and organic) weekly between July-October during 2011 and 2012. Aerobic colony, coliform, and Escherichia coli counts were determined using 3M Petri-films. Escherichia coli prevalence was determined by enrichment with recovered isolates subjected to BOX-PCR and multiplex PCR phylogenetic typing. Mean coliform count for in-field plants was 1.2 ± 0.1 log₁₀ CFU/g. The prevalence of E. coli was 0.8 and 7% for conventional and organic leafy vegetable samples, respectively. No AMR to therapeutically critical antibiotics was observed in E. coli recovered from in-field plants, though nine (13%, n=67) multi-drug resistant strains were identified. Escherichia coli was recovered from an irrigation water reservoir (27%, n = 15), sprinkler (40%, n = 35), soil (58%, n = 19), hand swabs (4%, n = 27), and compost (6%, n = 16) from the organic production system. Escherichia coli was recovered from ditch water (100%, n = 10), and soil (12%, n = 25) from the conventional production system. Four phylogenetic groups were recovered, with B1 E. coli being the predominant phylogroup (78%). Though 92% of recovered E. coli were unrelated, BOX-PCR revealed identical fingerprints for E. coli recovered from irrigation water or compost and in-field plants. In sum…
aggregated CHO: https://circle.library.ubc.ca/rest/handle/2429/44613
note: Examination of Microbiological Quality of In-field Leafy Vegetables and Identification of On-farm Generic Escherichia coli Transmission Dynamics by Jayde Lian Wood B.Sc., The University of British Columbia, 2011 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (Food Science) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) June 2013 © Jayde Lian Wood, 2013 ii Abstract Fresh produce has increasingly been linked to foodborne outbreaks in North America. Although contamination of produce may occur at any point along the food continuum, significant risks are thought to occur at the farm level. Data illustrating bacterial transmission dynamics on farm, however, are lacking. The aim of this project was to produce baseline data describing the occurrence of indicator bacteria on in-field leafy vegetables; examine antimicrobial resistance (AMR) of recovered Escherichia coli; and identify on-farm microbiological reservoirs impacting leafy vegetables. In-field plants (n=1093) and environmental samples (irrigation water, compost, soil, and hand swabs; n=316) were collected from two production systems (conventional and organic) weekly between July-October during 2011 and 2012. Aerobic colony, coliform, and Escherichia coli counts were determined using 3M Petri-films. Escherichia coli prevalence was determined by enrichment with recovered isolates subjected to BOX-PCR and multiplex PCR phylogenetic typing. Mean coliform count for in-field plants was 1.2 ± 0.1 log10 CFU/g. The prevalence of E. coli was 0.8 and 7% for conventional and organic leafy vegetable samples, respectively. No AMR to therapeutically critical antibiotics was observed in E. coli recovered from in-field plants, though nine (13%, n=67) multi-drug resistant strains were identified. Escherichia coli was recovered from an irrigation water reservoir (27%, n = 15), sprinkler (40%, n = 35), soil (58%, n = 19), hand swabs (4%, n = 27), and…
has type: Thesis/Dissertation
date issued: 2013-11
is shown at: 10.14288/1.0073924
language: eng
degree discipline: Food Science
provider: Vancouver : University of British Columbia Library
publisher: University of British Columbia
rights: Attribution-NonCommercial-NoDerivatives 4.0 International
rights URI: http://creativecommons.org/licenses/by-nc-nd/4.0/
scholar level: Graduate
type: Text
identifier URI: http://hdl.handle.net/2429/44613