Salmonella enterica and enterohemorrhagic escherichia coli on vegetable seeds – mechanism of attachment, fate during germination, and control
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The number of outbreaks of human gastrointestinal infection associated with the consumption of fresh produce has increased in recent years. Contaminated seeds have been identified as a potential source of vegetable contamination, especially the contamination of sprouts. The objectives of this study were to assess the abilities of selected Salmonella and enterohemorrhagic Escherichia coli strains to attach to vegetable seeds with different surface characteristics, to examine the physiological behavior of the bacterial pathogens on germinating seeds artificially contaminated by different approaches, and to evaluate the efficacy of treatment with probiotic tomato ferments on the fate of bacterial pathogens inoculated on alfalfa seeds and sprouts. We found that bacterial attachment to vegetable seeds was influenced by seed integrity but not by the fungicide treatments on seed surface. The mean populations of the pathogens on sprout/seedlings tissues developed from seeds contaminated by immersion into bacterial suspensions were significantly higher than those from seeds contaminated by contact with artificially-inoculated soil. Seed coats had the highest bacterial counts, followed by the roots and cotyledons; the stem tissues had the lowest pathogen counts. Treatment with filter-sterilized supernatants of probiotic tomato ferments significantly reduced the population of S. Cubana and E. coli F4546 on alfalfa seeds and sprouts. The study provides a better understanding on how pathogens attach to, and behave on germinating, vegetable seeds and the performance of tomato ferments for sanitizing sprout seeds and seed sprouts. This information will help reduce the economic losses associated with vegetable-related outbreaks of infections.