Submitted to: Journal of Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/23/2000
Publication Date: N/A
Interpretive Summary: Salmonella infection in pigs is a potential source of infection in human consumers of pork. Bacteria collected from the digestive tracts of pigs were used to develop two continuous-flow (CF) cultures, which inhibited the growth Salmonella. A CF culture is a bacterial culture that is maintained under constant growth by continually adding fresh medium. One culture, called pCF1, was made from bacteria collected from the digestive tract of a pig given feed that did not contain antibiotics, while the other culture, called pCF4, was made from digestive bacteria collected from a pig given feed containing the antibiotic chlortetracycline. Salmonella was added to both cultures at low, medium, and high levels. Both CF cultures of pig digestive bacteria inhibited the growth of Salmonella. The ability to limit Salmonella growth was not restricted by prior exposure of the digestive bacteria to chlortetracycline. The use of CF cultures offers an alternative method to antibiotic therapy as treatment for Salmonella infection in pigs. The results of this study are of interest to researchers, growers, and producers of swine products.
Technical Abstract: Porcine cecal bacteria were used to develop two anaerobic continuous-flow (CF) competitive exclusion (CE) cultures effective against in vitro colonisation by Salmonella typhimurium. One culture, pCF1, was derived from cecal bacteria collected from an animal given antibiotic-free feed, while the other culture, pCF4, was derived from cecal bacteria collected from an animal maintained on feed containing 200 g ton**-1 of chlortetracycline. Both cultures were challenged with each of 10**2, 10**4, and 10**6 Salmonella CFU ml**-1. Samples were taken at 24-h intervals and examined for Salmonella CFU ml**-1, anaerobic CFU ml**-1, pH, and volatile fatty acids. An inoculum of 10**2 Salmonella CFU ml**-1 resulted in no Salmonella being detected at 2 and 3 days after inoculation of pCF1 and pCF4, respectively. Challenges of 10**4 and 10**6 Salmonella CFU ml**-1 resulted in clearance of Salmonella from pCF1 and pCF4 by 4 days after challenge. The results indicated that in vitro continuous-flow cultures of porcine cecal bacteria were able to inhibit the growth of Salmonella. The ability to limit Salmonella growth was not restricted by prior exposure of the cecal bacteria to chlortetracycline. The use of continuous-flow competitive exclusion cultures may offer an alternative method to antibiotic therapy as prophylactic treatment for salmonellosis in pigs.