Submitted to: American Society of Animal Science Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/20/1998
Publication Date: N/A
Technical Abstract: Salmonella colonization and shedding in swine may result from various environmental and developmental stress factors. The incorporation in feed of subtherapeutic levels of selected antibiotics have been reported to influence Salmonella colonization and shedding. The application of competitive exclusion (CE) technologies has been used to reduce Salmonella spp. colonization in poultry. The concept of CE is the use of beneficial bacteria to reduce or eliminate colonization by enteropathogens. The objective of the present study is to determine the effect of the feed additive chlortetracycline (CTC) on the ability of CE bacteria to displace Salmonella typhimurium (ST) from a continuous-flow (CF) chemostat culture. CF cultures of CE bacteria were derived from cecal microflora collected from swine maintained on feed which contain either no added CTC or on feed containing CTC. In vitro chemostat cultures were inoculated with ST at 10**2, 10**4, or 10**6 cfu/ml. Samples were removed at twenty-four hour intervals and analyzed for ST. Regardless of the dosage, ST was reduced to undetectable levels in each chemostat vessel. Inoculation of the chemostat cultures with 10**2, 10**4, or 10**6 cfu/ml ST resulted in elimination of ST within 2-3, 3-4, or 4 days after inoculation, respectively. The CE culture derived from the swine given CTC-treated feed required one day longer to eliminate ST than the culture derived from swine microflora not given CTC. These data suggest that CTC may impact the swine microflora in the gut and leads to decreased ability of the microflora to inhibit ST colonization.