![[Dept. of Food Science]](http://njaes.rutgers.edu/_common/images/subheads/foodscience.gif "[Dept. of Food Science]"){kind=small}
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Research Interest
The microbial safety of food impacts consumers nationally and internationally. My research uses tools of biotechnology to address questions of survival and virulence of foodborne pathogens. More so than many other disciplines food microbiology is in continual flux; new pathogens emerge, long recognized pathogens re-emerge as problems, and consumer demands change. Research emphasis is in the areas of microbial safety of fresh fruits and vegetables and antimicrobial resistance of foodborne pathogens.
Interaction of enteric foodborne pathogens and plant tissue
Understanding the interaction of foodborne pathogens including Escherichia coli O157:H7 and Salmonella with seed sprouts and lettuce is important in the development of strategies to control foodborne illness linked to the consumption of fresh produce. Numerous factors can influence contamination of produce, including the use of manure as a fertilizer; contaminated agricultural water; hygiene practices of workers in the field, packinghouse and processing plant. Challenges exist with respect to devising and implementing measures to control and prevent contamination. To study the interaction of foodborne enteric pathogens with plants (alfalfa sprouts, lettuce) we use bacteria expressing green fluorescent protein (GFP) and fluorescent microspheres.
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Marker bacteria and fluorescent microspheres are visualized using fluorescence microscopy and laser scanning confocal microscopy. The marker bacteria can be incorporated into soil, manure or suspended in water and the association and localization with the crop of interest determined. Our research demonstrated that alfalfa sprouts and lettuce plants are capable of localizing bacteria and fluorescent microspheres at internal locations. |
Photomicrograph (To left) showing the presence of FluospheresÔ in the internal portions of stem sections of a lettuce plant. The lettuce plants were irrigated with water containing the fluorescent microspheres avoiding contact with the edible portion of the plant. The microspheres ultimately localized in the edible portion of the plant. Leaf sections were excised and mounted so that the internal portion of the central vein was viewable using Laser Scanning Confocal Microscopy. Orthogonal (stacked) projection of 14 z-section scans (taken at intervals of 10 mm) of FluospheresÔ associated with internal portions of lettuce stem tissue. Note FluospheresÔ are clustered in the central region of the lettuce stem tissue section. The bar represents 100 μm. |
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Bacteria at internal locations would not be removed through washing or killed by the application of a sanitizer. Research studies are on going to further define the interaction of enteric foodborne pathogens with plant tissue (fresh fruits and vegetables).
Food: Its role in facilitating gene transfer and antimicrobial Resistance
Microorganisms associated with food may carry antibiotic resistance genes or have intrinsic mechanism that facilitates survival in the presence of sub-lethal concentration of sanitizer. Two lines of research address antimicrobial resistance: Antimicrobial resistance of Salmonella is associated with recombination and transfer of resistance genes. Antimicrobial resistance associated with intrinsic mechanisms is often overlooked. This not only holds true for antibiotics, but for other antimicrobial agents as well. The mar operon, located on the chromosome of Enterobacteriaceae, is one intrinsic mechanisms of antimicrobial resistance. In this study bacteria were exposed to food preservatives or sanitizing compounds and cross-resistance or decreased resistance to antibiotics tested. Results suggested that exposure of Salmonella to chlorine and food preservatives induce the mar phenotype. |
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The enterococci are commensal lactic acid bacteria of the gastrointestinal tract of humans and animals, and are ubiquitous in nature. In the United States, the development and prevalence of vancomycin-resistant enterococci (VRE) has been linked to widespread clinical use of vancomycin. In Europe, VRE persist among food animals following the agricultural use of avoparcin, a glycopeptide growth promoter that was banned in 1997. Today, VRE are the third most prevalent nosocomial pathogen in the United States. Recent genotypic data demonstrate homogeneity among global VRE isolated from food, animals, healthy human carriers and hospital inpatients, indicating that transfer of the resistance phenotype occurs among multiple reservoirs. This raises concern over the potential for prepared foods to become contaminated with VRE through raw or processed ingredients, food handlers, or the environment. Horizontal transfer of resistance genes between gram-positive bacteria is mediated via mobile transposable elements that harbor vanA and vanB resistance genes on conjugative plasmids. Aggregation proteins and sex pheromones that induce conjugation between enterococci have been identified, but the role of these virulence factors in enterococci of food origin is largely unknown.