Title page for ETD etd-12042008-234638

Type of Document Master's Thesis
Author Hintz, Leslie Diane
Author's Email Address Lehintz@vt.edu
URN etd-12042008-234638
Title Association of Salmonella enterica serotype Newport with Tomato Plants through Irrigation Water, Grown under Controlled Environmental Conditions
Degree Master of Science
Department Food Science and Technology
Advisory Committee
Advisor Name Title
Boyer, Renee R. Committee Chair
Ponder, Monica A. Committee Member
Rideout, Steven L. Committee Member
Williams, Robert C. Committee Member
  • Tomato
  • Salmonella
  • irrigation water
Date of Defense 2008-11-21
Availability unrestricted
Tomato fruit have been associated with numerous outbreaks of salmonellosis in recent years. Trace back suggests tomato fruit may become contaminated during pre-harvest, however exact routes are unclear. The objective of this study was to determine the potential for Salmonella enterica serotype Newport to be associated with the roots, leaves, stems, and ultimately fruit of red round tomato plants through contaminated irrigation water, at various stages of plant development, when grown under controlled environmental conditions. Tomato plants were individually root irrigated with 250 or 350 ml (depending on growth stage) of 7 log CFU/ml S. Newport contaminated irrigation water every seven days. Presence of the pathogen in plant tissue was evaluated at five growth stages; 14 days post transplant, early fruit, mid fruit, full fruit, and terminal stages. At each stage, roots, stems, leaves, and two tomato fruit, if present, from four S. Newport and four water irrigated (negative control) tomato plants were sampled for S. Newport contamination. Association of S. Newport was detected in tomato roots and stems using both conventional plating and molecular techniques. Twenty-four samples were confirmed positive for S. enterica using PCR. Sixty-five percent of the roots, 40% of the stems, 5% of the leaves and 5% of the fruit sampled were confirmed to contain S. enterica. Overall, there was significant difference in the presence of S. Newport according to tissue sampled (roots > stems > leaves and fruit) (P > 0.05). There was no correlation between growth stage and presence of S. Newport in tissues (P > 0.05). Ultimately, irrigation with S. Newport has a low probability of contaminating tomato fruit.
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