Salmonella Internalization From Contaminated Seeds or Irrigation Water in Greenhouse Tomatoes
Miles, Jacquelyn Marie
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Abstract 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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