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Evaluate Dissemination and Persistence of Antimicrobial Resistant Salmonella and Shiga Toxin-Producing Escherichia Coli Following Land Application of Swine Manure

Thakur, Siddhartha; Jacob, Megan
North Carolina State University
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1) Determine the dissemination and persistence of Salmonella and STEC on land following manure application from commercial swine farms; and

2) Characterize and compare the isolates from different sources on farm and environment using phenotypic and genotypic approaches.

Expected Outcome: The proposed study will provide definite answers including:

a) advance our understanding of the impact of swine manure application on land in terms of survivability and persistence of Salmonella and STEC, and;

b) determine the impact of swine manure management program and other farm management practices on the movement of Salmonella and STEC in the environment.

More information

The mechanisms associated with dissemination and persistence of foodborne pathogens from US pork and other food animal industries are a national priority. Two of these organisms, Salmonella and Shiga toxin-producing Escherichia coli (STEC) are frequent targets of interventions and are common in pigs. It will be important to understand the ecology of these pathogens within the animal and in the environment to develop control strategies as well as help monitor the spread of antimicrobial resistance. We propose to conduct a study on five commercial swine farms, which will provide important information on the dissemination and persistence of AR Salmonella and STEC in the environment following land application of swine manure. Our proposal will close gaps in our understanding of the dissemination and persistence of Salmonella and STEC from the swine farm to land located close to these farms.

The sampling will be conducted on 5 swine farms in North Carolina. Salmonella status will be based on previous Salmonella research conducted on the farm or from information provided by the company. Farm environmental samples will be collected from each of the five different swine farm sites in NC. The samples will consist of lagoon/manure pit and soil where the manure will be applied. We will work closely with the swine producers to determine the manure application schedule and work accordingly. Soil samples will be collected from one acre size of land (88x55 yards) and from four different locations within a plot including a distance of 20, 40, 60 and 80 yards within the manure application area. Each location will be divided into 5 grids of 1m2 size each and soil samples will be collected from within these grids. Therefore, on each sampling time point we will collect a total of 20 samples (5 samples/location x 4 locations). The first set of samples will be collected on day 0 (application of swine manure on land) two hours before and then two hours after manure application. This will be done to determine the background status of Salmonella and STEC on the land before manure application and the impact immediately after manure application. Soil samples from the farm environment will be collected again on day 7 and day 14 following deposition of swine manure. The aim of multiple sampling at different time points is to determine whether or not AR Salmonella and STEC persist in the environment 7 and 14 days post manure application. The proposed sampling design (particularly, the time points) was developed, based on the study reported by Boes et al. (2005) with slight modifications. Pertinent management, facility and herd information potentially associated with the dissemination and persistence of Salmonella and STEC in pigs and the environment will be collected. Analysis of variance (ANOVA) for repeated measures will be done with SigmaPlot 11.2 (Systat Software Inc., Chicago, IL) for comparing Salmonella and STEC prevalence and antimicrobial resistance profile from swine manure and the environment for the different time points. We will determine the strength of association between Salmonella and STEC serotype, resistance pattern isolated from the swine manure and environment with the waste management program and antimicrobial use on farm using the odds ratio (OR) with a 95% confidence interval (Egret software version 2.0.3, Cytel Corp., Cambridge, MA). A value of P < 0.05 will be considered statistically significant.

Funding Source
Nat'l. Inst. of Food and Agriculture
Project source
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Escherichia coli
Antimicrobial Resistance
Bacterial Pathogens
Meat, Poultry, Game