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The objective of this proposal is to use a molecular epidemiologic approach to determine whether eliminating the use of antibiotic growth promoters has adverse affects on public health, reduces the health of swine, and whether antibiotic growth promoters mediate their effects by alteration of the intestinal bacterial microflora. Public health concerns include whether halting the use of antibiotic growth promoters results in increased carriage or load of food borne pathogens. There are 3 interrelated specific aims that will be addressed in this study using a common longitudinal field-based crossover study design: <ol>
<li> To determine whether tylosin, an antibiotic growth promoter, causes measurable and stable changes to the normal intestinal microflora of treated animals. <li> To quantitatively measure changes in food borne zoonotic pathogens in animals in response to use of tylosin. The target organism will be Salmonella enterica. <li> To determine whether tylosin treatment results in enhanced animal health. Two measurements will be employed: measurement of the levels of acute phase proteins and average daily weight gain will be used as indicators of animal health. </ol>
NON-TECHNICAL SUMMARY: The use of antibiotics results in selection of antibiotic resistance in bacteria. There are growing concerns about public health effects associated with the selection of antibiotic resistant bacteria in livestock, and this has led to mounting pressure to reduce or eliminate the use of antibiotics for the sole purpose of growth promotion in livestock. However, reducing the use of antibiotic growth promoters could result in increased carriage of food borne pathogens by livestock, an overall reduction in health of these animals, and the need for greater use of therapeutic dosages of antibiotics to treat sick animals. This project is designed to determine if the use of antibiotic growth promoters affect animal health and result in pigs carrying more of few food borne pathogens.
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APPROACH: This project will utilize a crossover study design with two initial groups of pigs: one receiving tylosin, the other will not receive tylosin. Fecal samples and occasional serum samples will be collected and pigs will be weighed weekly. This regimen will continue for 14 weeks after which each group will be split in half and one will receive tylosin and the other will not. Microflora content and diversity will be measured using T-RFLP and sequencing of 16S rDNA. Salmonella enterica levels will be measured by quantitative culture techniques employing a most probable number scheme. Health status will be determined based on weight gain and levels of C-reactive protein (a measure of inflammation).