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Understanding of Salmonella-phytopathogen-environment-plant interactions and development of novel antimicrobial to reduce the Salmonella burden in fresh tomato production

Deblais, Loic
http://rave.ohiolink.edu/etdc/view?acc_num=osu1534437638478448

Abstract Details

2018, Doctor of Philosophy, Ohio State University, Plant Pathology.
Salmonellosis cases caused by Salmonella enterica through pre-harvest contamination of fresh produce represent a risk to human health worldwide; however, little is known about the interactions between Salmonella, phytopathogens, environment, and the plant host contributing to this food safety issue. Furthermore, the control of Salmonella from “farm to fork” is challenging due to the development of resistance mechanisms towards current control methods and restrictions on use of antimicrobials imposed by regulatory agencies. We investigated the effects of specific environmental conditions on the persistence and dissemination of Salmonella enterica subsp. enterica serotype Typhimurium (S. Typhimurium) following artificial contamination of `Tiny Tim’ tomato plants. We found that higher temperatures (30°C day/25°C night) reduced the persistence of S. Typhimurium in the phyllosphere compared to lower temperatures (20°C day/15°C night) when plants were sprayed on the leaves with a S. Typhimurium -contaminated solution. Wounding cotyledons with contaminated tools increased S. Typhimurium persistence and internalization in planta compared to spray inoculation. Low relative humidity enhanced the dissemination of Salmonella into non-inoculated plant tissues. S. Typhimurium was detected in the root systems for at least 98 days-post inoculation. Further, we showed that splice-grafting (`Celebrity’ with ’MaxiFort’) is a major risk for the internalization and long-term survival of S. Typhimurium inside the tomato plant. S. Typhimurium was detected in the root system for over 137 days if at least 5 x 10^3 colony-forming units were introduced during grafting. The survival of S. Typhimurium in tomato foliage was also affected by the presence of phytopathogens, the genotype of S. Typhimurium and tomato variety used. We found that rfbV, involved in O antigen synthesis, might be essential for S. Typhimurium persistence in inoculated tomato plants and especially in `Tiny Tim’ plants. Further, S. Typhimurium reduced the population of Clavibacter michiganensis subsp. michiganensis and Xanthomonas gardneri in co-inoculated `Tiny Tim’ tomato plants. In vitro data revealed that several Salmonella serotypes including S. Typhimurium secrete antimicrobial molecule(s) in the supernatant inhibiting the growth of numerous phytopathogens and with limited effect on biocontrol agents. The antimicrobial molecule(s) seems to be proteolysis- (proteinase K) and thermo- (autoclaved) resistant and with a molecular weight lower than 3 kDa. We investigated the antimicrobial activity of a library of 4,182 pre-selected small molecules (SMs) against S. Typhimurium. Four growth inhibitor SMs were effective at 10 µM (and higher) against several Salmonella serotypes, and antibiotic-resistant and biofilm embedded S. Typhimurium. Cytological studies suggested that they act by altering cell membrane integrity. The four SMs combined with Bacillus amyloliquefaciens strain BA1 and Enterobacter sp. strain BCA enhanced the suppression of S. Typhimurium in tomato plants, and displayed no toxic effect on tomato seeds, seedlings, or fruits at 200 µM. The real-time bioluminescent imaging system revealed that stem scar is a difficult site for S. Typhimurium decontamination. Further the four SMs reduced S. Typhimurium population in ceca and its translocation into systemic organs in chickens, with minimal impact on the cecal microbiota. The four SMs also displayed synergistic effects with antibiotics effective against Salmonella (ciprofloxacin, meropenem and cefeprime).
Gireesh Rajashekara (Advisor)
Sally Miller (Advisor)
Laurence Madden (Committee Member)
Christopher Taylor (Committee Member)
Corey Nislow (Committee Member)
332 p.
Agriculture; Bioinformatics; Biology; Environmental Health; Molecular Biology; Plant Pathology; Public Health
Salmonella enterica; tomato production; fresh produce; whole genome sequencing; microbiota; small molecules; growth inhibitors; plant pathogenic bacteria; relative humidity; temperature; grafting; chicken; supernatant; antimicrobials; Typhimurium; rfbV

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Citations

  • Deblais, L. (2018). Understanding of Salmonella-phytopathogen-environment-plant interactions and development of novel antimicrobial to reduce the Salmonella burden in fresh tomato production [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1534437638478448

    APA Style (7th edition)

  • Deblais, Loic. Understanding of Salmonella-phytopathogen-environment-plant interactions and development of novel antimicrobial to reduce the Salmonella burden in fresh tomato production. 2018. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1534437638478448.

    MLA Style (8th edition)

  • Deblais, Loic. "Understanding of Salmonella-phytopathogen-environment-plant interactions and development of novel antimicrobial to reduce the Salmonella burden in fresh tomato production." Doctoral dissertation, Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1534437638478448

    Chicago Manual of Style (17th edition)

osu1534437638478448
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