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Abstract
The emergence of multi-drug resistance in Salmonella typhimurium and Salmonella newport, has sparked increased debate over the impact of veterinary usage of antibiotics on the development of resistance. For drug resistance to develop in Salmonella, there must be a reservoir of mobile, antibiotic resistance genes. Newly hatched commercial broiler chicks were orally inoculated with S. typhimurium nalidixic acid-rifampicin resistant isolates and subsequently administered intestinal microflora composed of poultry litter containing antibiotic resistant enteric bacteria collected from a commercial broiler chicken farm, which was propagated in specific-pathogen free (SPF) chickens. For six- weeks, the typical maturation period for commercial poultry, resistance transfer to Salmonella was monitored weekly by plating tetrathionate enrichments onto XLT4 selective media supplemented with antibiotics. At the end of the six-week study, resistant Salmonella were enumerated by a modified three-tube MPN procedure.