Genotypic and phenotypic comparison of swine Salmonella isolates from farm and abattoir

Matthew M. Erdman, BS; Stephanie D. Wedel, BS; D.L. Harris, DVM, PhD

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Objectives: To determine if pigs became infected with different serotypes of Salmonella following transport and lairage, and whether genotypic and phenotypic analysis would identify different subtypes within the same serotypes.

Methods: Salmonella organisms were isolated from lymph nodes of pigs from three herds (A,B,C) at the abattoir, and isolates were compared to those previously cultured from fecal samples from two of the herds (A,B). The farms were located in three different states within the United States, and pigs were transported to the same abattoir in separate clean and disinfected vehicles. Serotyping, antibiotic resistance profiling, and genetic fingerprinting using pulsed- field gel electrophoresis were used to compare isolates.

Results: Salmonella serovars recovered from feces of pigs from farms A and B were also recovered from lymph nodes of pigs from the same farm. Additionally, isolates cultured from pigs at the abattoir were distinguishable from those cultured from pigs on the source farm by identification of serovars, genetic fingerprinting within serovars, and antibiotic resistance profiles.

Implications: Biosecurity, from the time market pigs leave the farm up to and including the hours immediately prior to slaughter, is crucial to the control of salmonellae in pork. New populations of salmonellae, not previously present on the source farm, may be recovered from pigs at the abattoir. Rapid infection may occur in pigs not previously harboring Salmonella organisms, and the strain may be multi-antibiotic resistant, further elevating the food safety risk.

Keywords: Salmonella, food safety, pulsed-field gel electrophoresis, antibiotic resistance

RIS citationCite as: Erdman MM, Wedel SD, Harris DL. Genotypic and phenotypic comparison of swine Salmonella isolates from farm and abattoir. J Swine Health Prod 2003;11(4):169-172.

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