INSIGHTS ALONG THE PATH TO SUSTAINABILITY| November 30, 2005
The Impact of Poultry Litter as Fertilizer on the Bacteriological Quality of Leafy Vegetables JAY P. GRAHAM, MBA, MPH, Doctoral Candidate, Department of Environmental Health Sciences, JHSPH SUMMARY Antimicrobial resistance (AMR) in human pathogens is an increasingly serious public health problem in the US and world wide (1). It is well documented that use of antimicrobial drugs is associated with increased risks of food-borne infections, including infections by AMR pathogens (2). Much less attention, however, has been given to the entrance of antimicrobial resistant pathogens as well as genetic determinants conferring resistance into the environment through the widespread practice of land disposal of animal wastes.
It is estimated that 5.6 million tons of poultry litter (containing excreta, animal carcasses, spilled feed and bedding material) is applied to land in the U.S. each year (3). To date, most research has focused primarily on potential ecological impacts of animal biosolid disposal, associated with nutrient overloading of aquatic systems. In addition to nutrients, however, this waste also contains the constituents of animal feed (including antimicrobials) and large numbers of microorganisms (4). The microorganisms include AMR strains of pathogenic and non-pathogenic bacteria, resulting from the use of antimicrobials for growth promotion and disease prevention in poultry production. Use of antimicrobials in poultry production has been shown to be associated with the occurrence of AMR in bacteria from poultry litter (5). Even when use of antimicrobials is discontinued, a high prevalence of resistance genes are found to persist (6). When applied to fields, resistant bacteria and AMR genes are passed on to this environment, which can lead to the horizontal transfer of resistance genes to indigenous soil bacteria (7). In addition, it is estimated that 75% of antimicrobials used in food animal production is excreted, providing selection pressure for AMR in the environment (8).
This study will include collection and analysis of fresh and stored poultry litter, soil amended with poultry litter, and lettuce grown on these soils for AMR bacteria and resistance genes. Antimicrobial resistant bacteria, pathogenic or non-pathogenic, present in poultry litter may be transferred to crops raised in soil amended with poultry litter. PRESENTER BIOGRAPHY Jay Graham is currently a doctoral candidate in the Department of Environmental Health Sciences at Johns Hopkins Bloomberg School of Public Health. Prior to entering the PhD program, Jay worked at the Center for Environmental Resource Management (CERM) at the University of Texas at El Paso, where he specialized in the planning, management, and evaluation of environmental health research and outreach projects on the U.S.-México border. Most of his research efforts at CERM focused on issues related to water quality, sanitation, and hygiene, based on the fact that a large number of households living on the border lack piped water and sanitation infrastructure. More recently, Jay’s research has shifted to the environmental health impacts associated with land disposal of animal wastes from concentrated animal feeding operations (CAFOs). His research is predominantly focused on the health impacts associated with the use of pharmaceuticals, including antibiotics, in food-animal production.
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