Title page for ETD etd-12012006-144716

Type of Document Master's Thesis
Author Miles, Jacquelyn Marie
URN etd-12012006-144716
Title Salmonella Internalization From Contaminated Seeds or Irrigation Water in Greenhouse Tomatoes
Degree Master of Science In the Life Sciences
Department Food Science and Technology
Advisory Committee
Advisor Name Title
Sumner, Susan S. Committee Chair
Latimer, Joyce G. Committee Member
Williams, Robert C. Committee Member
  • Salmonella
  • tomatoes
  • fertilizer
Date of Defense 2006-11-17
Availability unrestricted

Greenhouse grown tomato fruits and tissues were tested for the presence of

Salmonella after the plants had been treated with Salmonella contaminated irrigation

water or grown from contaminated seeds. Greenhouse grown tomato plants were placed

into eight different groups. Groups one through six consisted of five plants each and were

treated with 350 ml of 10^6 Salmonella contaminated irrigation water over a course of 70

days; group one received one 350 ml 10^7 Salmonella treatment, group two received two

treatments, and so on, the treatments were scheduled every 14 days. Group seven was the

control that consisted of five plants and received no Salmonella treatment. Group eight

was grown from seeds that had been contaminated with Salmonella by soaking the seeds

in a 10^8 Salmonella suspension for 24 hours at room temperature, and received no

Salmonella watering treatment. A total of 128 tomatoes were sampled from the tomato

plants of all three groups and none tested positive for Salmonella. Tissue samples

consisting of roots, leaves, and stems, and were collected from one plant per each of three

replications. No leaves or stems contained Salmonella, however, five of the twenty-four

root samples were positive for Salmonella.

In a second study, Salmonella was tested for its ability to survive in three

concentrated fertilizer stock solutions and 1.6% diluted solutions of the fertilizer.

Fertilizer sample CF-S was a stock solution of commercial 20N-4.4P-16.6K fertilizer,

US-S was a mix of 11.3 kg UltraSol, 4.5 kg Epsom Salts, and 2.3 kg 0N-0P-43.2K in

114 L water, Fertilizer CN-S is a mix of 11.3 kg Calcium Nitrate and 56.7 g Iron chelate

(10%) to 30 L water; Fertilizers CF-1.6, US-1.6, and CN-1.6 were the 1.6% fertilizer

dilutions respectively. There was no significant difference (p<0.05) between the survival

of Salmonella in fertilizer groups CF-1.6, US-S, US-1.6, CN-1.6, and the sterile distilled

water control; all but US-S yielded less than a one log reduction in Salmonella over a

period of 72 hours. US-S yielded over a two log reduction in Salmonella and was not

significantly different than CN-S which had over a four log reduction. CF-S was

significantly different than all samples and led to over a 6 log reduction of Salmonella.

The results of this study showed no evidence that Salmonella was able to

internalize in Cultiver trust tomato fruit or tissues above the root line when irrigated with

contaminated water into the pine medium under greenhouse conditions. There was also

no evidence that Salmonella is able to internalize in any tissues or fruit from

contaminated seeds. The results also show that Salmonella was not able to survive in the

commercial fertilizer stock solution (CF-S), and had limited survival in CN-S tomato

fertilizer solution. The diluted fertilizer solution and US-S stock solution showed no

significance in survival of Salmonella when compared to the sterile water control.

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