Ecology of Salmonella and its acquisition of antibiotic resistance in an integrated broiler production system
Liljebjelke, Karen Anne
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In order to understand the ecology of Salmonella within an integrated commercial broiler production system, 289 Salmonella enterica were recovered from two integrated poultry farms during the production and processing of seven consecutive flocks. The variety and prevalence of Salmonella serotypes differed between farms, with fifteen serotypes identified. Salmonella Typhimurium and Enteritidis recovered from processed carcasses from Farm One were characterized using pulsed-field gel electrophoresis, and were indistinguishable from isolates recovered from the poultry house environment and mice trapped on this farm. Combining isolates from both farms, 61.9 percent were pan-sensitive to a panel of eighteen antimicrobials used in the National Antimicrobial Resistance Monitoring Service (NARMS) surveillance. Combinations of resistance against streptomycin, gentamicin, sulfamethoxazole, trimethoprim, and tetracycline, were observed for a variety of S. enterica serotypes and PFGE genetic types. Among all serotypes, 87.3 percent contained the class 1 integron marker, intI1. Resistance to streptomycin, gentamicin, sulfamethoxazole, trimethoprim, and ampicillin was positively correlated (p < 0.05) with presence of intI1, a marker for the class 1 integron. Results indicate that management practices at the breeder level may have a profound effect on the transmission and persistence of salmonellae within an integrated production system.