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Title: Comparison of Subtyping Methods for Differentiating Salmonella enterica Serovar Typhimurium Isolates Obtained from Food Animal Sources

Author
item FOLEY, STEVEN - NATIONAL FARM MEDICINE
item WHITE, DAVID - FDA-CVM
item MCDERMOTT, PATRICK - FDA-CVM
item WALKER, ROBERT - FDA-CVM
item RHODES, BOBBIE - UNIV CENTRAL ARKANSAS
item Cray, Paula
item SIMJEE, SHABBIR - FDA-CVM
item ZHAO, SHAOHUA - FDA-CVM

Submitted to: Journal of Clinical Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/23/2006
Publication Date: 10/1/2006
Citation: Foley, S.L., White, D.G., Mcdermott, P.F., Walker, R.D., Rhodes, B., Cray, P.J., Simjee, S., Zhao, S. 2006. Comparison of Subtyping Methods for Differentiating Salmonella enterica Serovar Typhimurium Isolates from Food Animal Sources. Journal of Clinical Microbiology. 44(10):3569-3577.

Interpretive Summary: Salmonella is a zoonotic pathogen which can be transferred from animals to humans, most often through consumption of contaminated food. Infection with Salmonella can cause mild to severe gastroenteritis in humans while infection in food animals is often with clinical signs of disease. Molecular characterization (e.g. DNA-based typing methods) of Salmonella isolates is frequently employed to compare and distinguish clinical isolates recovered from animals, foodborne disease and nosocomial infections. In this study, we compared the ability of different phenotyping and genotyping methods to distinguish isolates of Salmonella enterica serovar Typhimurium from different food animal sources. One-hundred twenty eight S. enterica serovar Typhimurium strains isolated from cattle, pigs, chickens and turkeys or derived food products were characterized using pulsed-field gel electrophoresis (PFGE), repetitive element PCR (Rep-PCR), multilocus sequence typing (MLST), plasmid profiling and antimicrobial susceptibility. The molecular typing methods, PFGE, MLST, and Rep-PCR, demonstrated the best discriminatory power among Salmonella isolates. However, no apparent correlation existed between the results of one molecular typing method and the others, suggesting that a combination of multiple methods is needed to differentiate S. Typhimurium isolates that genetically cluster using particular typing methods. These data are necessary to enable a more informed debate among scientists, commodity groups, government regulators, and animal industry personnel on the feasibility and likely efficacy of differentiating between Salmonella and as a means to reduce the incidence of animal and human salmonellosis.

Technical Abstract: Molecular characterization (e.g. DNA-based typing methods) of Salmonella isolates is frequently employed to compare and distinguish clinical isolates recovered from animals, foodborne disease and nosocomial infections. In this study, we compared the ability of different phenotyping and genotyping methods to distinguish isolates of Salmonella enterica serovar Typhimurium from different food animal sources. One-hundred twenty eight S. enterica serovar Typhimurium strains isolated from cattle, pigs, chickens and turkeys or derived food products were characterized using pulsed-field gel electrophoresis (PFGE), repetitive element PCR (Rep-PCR), multilocus sequence typing (MLST), plasmid profiling and antimicrobial susceptibility. Among the 128 Salmonella tested, we observed 84 Rep-PCR profiles, 86 PFGE patterns, 89 MLST patterns, 36 plasmid profiles, and 38 susceptibility profiles. The molecular typing methods, PFGE, MLST, and Rep-PCR, demonstrated the best discriminatory power among Salmonella isolates. However, no apparent correlation existed between the results of one molecular typing method and the others, suggesting that a combination of multiple methods is needed to differentiate S. Typhimurium isolates that genetically cluster using particular typing methods.