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An Integrated Approach to Determine Salmonella Dynamics in the Niche-Market Antimicrobial-Free Swine Production System

Investigators
Gebreyes, Wondwossen; Thakur, Siddhartha
Institutions
North Carolina State University
Start date
2008
End date
2011
Objective
The goal of the proposed integrated study is to determine the epidemiology and risk factors that aid in the dissemination and persistence of antimicrobial resistant Salmonella among swine reared in the intensive (indoor) and the extensive (outdoor) antimicrobial free (ABF) production system. An important component of this proposal is the preparation and evaluation of extension and education material for the stakeholders that will provide them pertinent information on the best practices to be undertaken to maximize pre-harvest food safety. The proposal will address two important priority areas of the National Integrated Food Safety Initiative priority areas including: 1) Filling knowledge gap about sources and persistence of microbial pathogens in meat and applying control measures to reduce these pathogens (111.D), and 2) Providing food safety education and training for farmers, industry and small farm vendors and processors (111.B) This will be the first longitudinal study conducted in the US to determine the risk factors that are responsible for the dissemination and persistence of antimicrobial resistant Salmonella in the ABF production system.

With this information, we plan to achieve our long term goal of reducing the burden of pork associated human cases of salmonellosis by pursuing these objectives:

  1. Research Objectives: 1.1) To determine the sources of Salmonella in the intensive and extensive ABF production systems on farm and at slaughter. 1.2) To compare the distribution of antimicrobial resistant Salmonella among ABF pigs and their environment at the phenotypic and genotypic levels. 1.3) To identify the risk factors at the ecological and management levels that are associated with the dissemination and persistence of Salmonella among ABF pigs.
  2. Education Objectives: To develop and implement new curricula aimed at providing education and training of veterinary, animal and food science students for generating a safe and wholesome ABF pork.
  3. Extension Objectives: To convey the results of the study to stakeholders including swine producers, swine veterinarians and production companies via seminars and gatherings and address the crucial aspects that will make the final pork product safe for human consumption.
Expected Results. The results will provide important information to stakeholders regarding dissemination and persistence of antimicrobial resistant Salmonella in the different ABF system which is currently not well defined in the United States. We expect the outcome of our education component will result in a better trained and educated student in veterinary, animal or food sciences focus. We believe the student will be more aware of the challenges posed by the foodborne pathogens in the pre-harvest food safety area and ways to counteract them. The information generated in this study using a scientific approach will greatly benefit the ABF swine industry by providing them options to mitigate Salmonella challenge at farm and slaughter. We strongly believe in that this study will provide the groundwork to conduct quantitative risk assessments in various ABF swine production systems.
More information
NON-TECHNICAL SUMMARY: Non-typhoidal Salmonella serovars have been known to be among the most common bacterial foodborne pathogens worldwide, and are known to be important reservoirs of antimicrobial resistance. There is an increasing emphasis on eliminating Salmonella in swine during pre-harvest production, and in swine-products during post-harvest processing in order to ensure the safest pork for human consumption. Recent increases in demand for niche-market antimicrobial-free (ABF) pork highlight the importance to determine Salmonella dynamics in these production systems. The goal of our integrated longitudinal study is to determine the epidemiology and risk factors that aid in the dissemination and persistence of antimicrobial-resistant Salmonella among swine reared in both intensive (indoor) and the extensive (outdoor) ABF production systems. Our central hypothesis is that unique sets of conditions (e.g., exposure to variable management and environment) in the two major ABF systems favors the dissemination and persistence of antimicrobial-resistant Salmonella strains that colonize and persist in the host and their environment. This longitudinal study is the first study of its kind in the US and will focus on defining the role played by ecological and management risk factors in the emergence, dissemination and persistence of antimicrobial resistant Salmonella in ABF swine production systems. Integral to this project is the preparation and evaluation of extension and education materials for swine-industry stakeholders that will provide them pertinent information on the best practices to be undertaken to maximize pre-harvest food safety.

APPROACH: Sample Collection and Processing: A total of 20 farms (30 pigs per farm) will be included in the study including 10 farms each from the intensive and extensive ABF farms with pigs sampled twice at nursery and finishing stages. Sample collection at the slaughter plant will include post-evisceration and post-chill samples stages and the mesenteric lymph nodes. Environmental samples will include five samples each of the barn and truck floor drag swabs. We will also collect feed and soil samples (5 samples weighing approximately 10 gm each in sterile whirl pack bags). Salmonella isolation will be done following standard bacteriological methods. Pertinent management and herd data that could play a role in dissemination and persistence of Salmonella in pigs will be collected. Salmonella Characterization: We will follow the Kauffman-White scheme for serotyping Salmonella. Antimicrobial susceptibility testing will be done using the broth microdilution method to determine the minimum inhibitory concentration (MIC) against a panel of 15 antimicrobials following the manufacturer recommendations. Salmonella isolates will be genotyped using Pulsed Field Gel Electrophoresis as recommended by CDC. We will use polymerase chain reaction for characterizing the genes, integrons and transposons coding for antimicrobial resistance. We will sequence the resistance coding regions to determine how similar or dissimilar they are from different sources. Data Analysis: Statistical analysis will be done for two outcome variables including the 1) presence of Salmonella in the fecal and environmental samples based on microbiological culture in the two ABF production systems at farm and slaughter and, 2) The occurrence of antimicrobial resistant Salmonella; exhibiting resistance to a single antimicrobial or multiple antimicrobials in the two production systems. The data for sample type including Salmonella positive samples, MIC values, serotype, antimicrobial resistance profile and patterns will be entered into a Microsoft Access database. All the data analyses will be run on SAS v.9.2. Education: Information generated in the study will be developed into educational materials and disseminated among veterinary, animal and food science students. We will combine the information generated in this study with pertinent pre- and post-harvest food safety issues that will be discussed with students in a didactic setting. Formal in class-evaluations of the material and information disseminated among the students will be collected. Extension: Information will be disseminated to the swine producers in the Healthy Hog Seminar series which is held every fall in North Carolina and attended by swine veterinarians, hog producers and stakeholders to exchange information pertaining to swine production. Data generated will also be presented at the North Carolina Veterinary Association meetings that are held six times a year. We will host four workshops in collaboration with NC A&T, Texas A&M and The Ohio State University. Evaluation of extension efforts will be performed using questionnaire survey at meetings as well as through links on the web site.

Funding Source
Nat'l. Inst. of Food and Agriculture
Project source
View this project
Project number
NCV-VMCG-0035
Accession number
214304
Categories
Bacterial Pathogens
Education and Training
Salmonella
Commodities
Meat, Poultry, Game