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Analysis of In-Plant Factors and Genotyping of Antimicrobial Resistance Among Four Organisms Isolated from Swine Processing Plants

Gebreyes, Wondwossen
Ohio State University
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End date
The main objective of the proposed research is to determine the role of periharvest factors (such as plant size, transport and lairage times, use of organic acids etc.) on selection and dissemination of antimicrobial resistant foodborne and commensal organisms.

The specific aims are:

  1. To determine the role of plant size and associated transportation, holding and in-plant practices on prevalence of resistant foodborne adn commensal organisms.
  2. To determine the clonality of strains identified from three different sizes of processing plants in two predominant pig producing geographic locations (NC and IA.
  3. To determine the distribution and similarity of specific antimicrobial resistance genes and class-1 integrons among four important organisms (Salmonella, Campylobacter, E. coli and enterococci) in the various processing settings.
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NON-TECHNICAL SUMMARY: Food products of animal origin, including pork, beef and poultry, are known to be important sources of foodborne disease outbreaks. The purpose of this project is to gain knowledge that will be important to the pork industry in its effort to control foodborne pathogens and their preliminary resistant forms.

APPROACH: Specific epidemiological and genotypic characterization procedures will be used to address the three specific aims listed above. The analytic epidemiological procedures will be conducted by the Research Triangle Institute. Phenotypic characterizations that hwve not thus far been completed will be done at the Ohio State University (OSU). All the genotypic characterizations will also be conducted at the Food Animal/Public Health Molecular Epidemiology Laboratory (IDMEDL) (OSU). The isolates that were collected in a pilot study will be further characterized in this study. Genotyping of Salmonella and Campylobacter using two DNA fingerprinting methods will be done. In addition, selected isolates from all four organisms will be tested for carriage of specific antimicrobial resistance genes and class-1 integron. Inially, a univariate analysis exploring the association between specimen type, plant characteristics and phenotypic and genotypic characteristics will be completed. Multivariate analysis will be used to provide a more thorough investigation of the univariate associations. Descriptive study determining the similarity of antimicrobial resistance genes and class-1 integrons between foodborne (Salmonella and Campylobacter) and indicator (Enterococcus and E. coli) will also be conducted.

PROGRESS: 2006/12 TO 2007/11
OUTPUTS: Samples were selected for genotypic characterization based on multi-drug resistance and association with other samples (groups of organisms that were from the same animal were selected). Review of the literature was done to identify resistance genes in the four organisms of interest. 236 genes were identified and organized by the four organisms. Priority of genes to be selected for PCR was accomplished by using the list created from the literature review. PCR analysis is preformed on these isolates based on their phenotypic characterization, looking to identify specific antimicrobial resistance genes and class-1 integrons. In addition, in collaboration with USDA-ARS, a microarray analysis has been done to determine the occurrence of various classes of antimicrobial resistance genes and similarity of carriage among the four organisms. Analysis was done specifically looking at similarity of genes in various organisms that were identified from individual pigs. In an event when we detected similar genes in the various organisms, further DNA sequencing was conducted to determine the level of similarity (homology) and a Phylogenetic analysis was conducted.
PARTICIPANTS: Dr. Wondwossen Gebreyes is an associate professor in the Department of Veterinary Preventive Medicine. He specializes in antimicrobial resistance, food safety and infectious disease molecular epidemiology.

IMPACT: 2006/12 TO 2007/11
Although all the organisms were isolated from each sample location, there were trends found in the location distribution. The majority of Campylobacter were found in the mesenteric lymph node (40.7%), enterococcus and E.coli were both most commonly found in the head meat (33.8% and 32.7%, respectively) and lairage swab (33.3% and 33.6%, respectively), and Salmonella was predominately found in the lairage swabs (52.7%). All four pathogens were highly resistant to tetracycline, with the lowest prevalence being in Salmonella at 69.4%. Resistance to macrolides, some aminogylosides (kanamycin and streptomycin), sulfamethoxazole, and â-lactams was also common. There was a great variety of resistance patterns found among the organisms with some overlapping patterns between Salmonella and E.coli. Multi-drug resistance patterns were highly variable, but commonly detected among all four organisms regardless of origin.The most common genes found were those encoding for tetracycline and aminoglycoside resistance.

Funding Source
Nat'l. Inst. of Food and Agriculture
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Bacterial Pathogens
Natural Toxins
Meat, Poultry, Game