Nutrition & Food Science

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End date: 2009Subject: search.filters.subject.Biology, Microbiology

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    Assessment of Foodborne Pathogen Survival During Production and Pre-harvest Application of Compost and Compost Tea
    (2009) Ingram, David Thomas; Joseph, Sam W; Meng, Jianghong; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The use of compost in crop production systems as a soil amendment is recognized by both conventional and organic plant production practitioners as a means to increase yields and reduce the incidence of foliar diseases. Compost tea (CT), an aqueous extract of the biological components of compost, is also recognized as a means to broadcast the phytopathogen-reducing components of compost directly to the surfaces of plants where many foliar diseases become established. CT has been shown to control the proliferation of a variety of foliar diseases in many turf, crop and horticulture production systems when applied directly to the foliar surfaces of plants. This dissertation research was designed to address several pre-harvest food safety issues concerning compost and compost teas. Three objectives were pursued to establish whether the use of compost and compost teas as pre-harvest practices may introduce foodborne pathogens into the food supply and, therefore, contribute to the incidence of foodborne illness. The first objective involved a microbiological survey of commercially available compost in the U.S. to determine the prevalence of fecal coliforms, Escherichia coli, Salmonella and enterococci that might be reaching consumers through contaminated fruit and vegetables. The second objective was to investigate the ability of these foodborne pathogens to propagate during the production of CT. The third objective involved a field study examining the potential of CT to disseminate E. coli into organic and conventional strawberry production systems. The effects of CT on the fruit yield, phytopathogen suppression, as well as the potential for foodborne pathogen survival on the fruit surfaces were examined. This project provided important information and recommendations for the safe production and pre-harvest application of compost and compost teas. It was contended that, with proper attention to the manufacture and storage of compost and with simple modification of current trends in CT production systems, the current threshold of pre-harvest introduction of foodborne pathogens could be significantly reduced.
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    Campylobacter jejuni/coli - Host Intestinal Epithelial Cell Interaction
    (2006-08-15) zheng, jie; meng, jianghong; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Campylobacter jejuni/coli have been known to be major bacterial causes of human gastroenteritis worldwide for decades. Regarding its pathogenicity, little is known yet. A better understanding of the pathogenic mechanisms will provide important information, not only for generating molecular markers to differentiate pathogenic strains versus non-pathogenic ones; but also for developing rational strategies to prevent and control Campylobacter-caused disease. The objectives of this study were to characterize the pathogenic abilities of various C. jejuni/coli retail meat isolates, including their abilities to adhere to, invade into and transmigrate across human epithelial cells, to examine the role of NF-κB pathway in IL-8 secretion induced by Campylobacter, and to identify C. jejuni-specific adherence/invasion genes during host pathogen interaction. It was found that the adherence and invasiveness of total 43 Campylobacter retail meat isolates in human intestinal epithelial T84 cell model indicated that C. jejuni/coli present in retail meat were considerably diverse in their ability to adhere to and invade human epithelial cells. Meanwhile, eight putative virulence genes, determined by PCR, were shown to be widespread among the Campylobacter isolates. C. jejuni /coli-induced proinflammatory cytokine Interleukin (IL)-8 secretion in polarized human colonic epithelial cells T84 was examined, and the role of NF-κB pathway in Campylobacter-induced IL-8 secretion was determined. Data suggested that C. jejuni/coli induce basolateral-polarized secretion of IL-8 in human intestinal epithelial cells, and C. jejuni-induced IL-8 secretion is NF-κB-dependent. The effort to identify C. jejuni-specific adherence/invasion genes during host pathogen interaction by using restriction fragment differential display PCR (RFDD-PCR) has been made. As a result, it was not successful. However this study still provides useful information and experience on the application of this technique for prokaryotic gene expression analysis during host pathogen interaction, which remains an unexplored area. In summary, Campylobacter retail meat isolates exhibited wide diversity in cell culture model in the ability of adherence, invasion and transmigration. As the first line defense, intestinal epithelium activates NF-κB and secretes proinflammatory cytokine IL-8 in response to Campylobacter infection. Multiple virulence factors have roles in Campylobacter-intestinal epithelial cell interaction.
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    Variations in 11B-Hydroxysteroid Dehydrogenase Type1 in Two Rat Models of Obesity
    (2006-05-04) Parsons, Erica Zager; Castonguay, Thomas W; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Obesity is an epidemic that has been estimated to cost the United States over $117 billion every year. Glucocorticoids have long been implicated in the maintenance of energy homeostasis due to their involvement with the hypothalamic-pituitary-adrenal axis. 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD-1) is an enzyme that interconverts the glucocorticoids cortisol and cortisone, and their rat counterparts corticosterone and 11-dehydrocorticosterone. We predicted an association between hepatic levels of this enzyme and either genetic obesity or dietary-induced obesity from any of two fat levels (high fat, low fat) or three fat sources (saturated, polyunsaturated, or monounsaturated). Our results indicated that hepatic 11β-HSD-1 is downregulated in genetic obesity, as has been previously found. High fat diets also caused reductions in hepatic enzyme message, although these were not statistically significant. There did not appear to be any effect of fat type.
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    Detection of norovirus and indicator organisms on fresh produce
    (2005-12-06) Williams, Karen Elizabeth; Meng, Jianghong; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Food borne illness is a major problem around the world. Recently, more food borne outbreaks involve produce as the vehicle and viruses as the source of contamination. Norovirus is a common food borne viral pathogen. Genetic diversity among the viruses has made detection difficult. Due to the difficulties in detection, the norovirus is an ideal candidate for having an indicator organism. FRNA bacteriophages share several similarities with enteric viruses and would be an ideal candidate. In this study, we evaluated reverse transcriptase polymerase chain reaction (RT-PCR) detection of norovirus and evaluated using FRNA bacteriophages, E. coli, and Enterococcus as indicator organisms for the virus on produce. Of the five RT-PCR methods tested, only two worked with both controls. Of the 180 produce samples tested, 37.2% were positive for FRNA bacteriophage, 17.2% were positive for Enterococcus, and 0% were positive for E. coli. We conclude that RT-PCR is not an efficient method for screening norovirus on produce and including FRNA bacteriophages as indicator organisms for viruses may help decrease outbreaks.
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    Effect of Acid Adaptation on the Thermal Inactivation of Listeria monocytogenes in Heating Menstrua Having Various Combinations of pH and Water Activities
    (2003-12-15) Edelson-Mammel, Sharon G; Joseph, Sam W; Food Science
    The impact of prior growth and food matrix conditions on thermal resistance of <i>L. monocytogenes</i>, a causative agent of the foodborne illness listeriosis, was evaluated in this study. In an initial study ( Main Study #1), acid induced and non-induced cells of thirteen strains of <i>Listeria monocytogenes</i> were placed into two heating menstrua: pH 3.0, water activity (Aw) 0.987 and pH 7.0, Aw 0.970. In twelve out of twenty-six combinations, non-induced cells were more heat resistant than induced cells. <i>L. monocytogenes</i> strain #201, in a follow-up study ( Main Study #2) using a factorial design to test additional combinations of water activity and pH heating menstrua, non-acid-induced cells generally were more heat resistant than acid-induced cells although the acid-induced cells showed greater thermal resistance in the heating menstrua having the lowest pH values. An increase in thermal resistance could lead to underestimation of treatments necessary to eliminate potential contamination by <i>L. monocytogenes</i>.