title: Molecular detection of the index case of a subclinical Salmonella Kentucky epidemic on a dairy farm.
abstract: Salmonella enterica commonly colonizes the intestinal tract of cattle and is a leading cause of foodborne illness. A previously described investigation into the prevalence of S. enterica on a dairy farm revealed an 8-year-long asymptomatic S. enterica epidemic caused by serotypes Cerro and Kentucky in the lactating herd. To investigate the source of the S. Kentucky strains, the genomes of two S. Kentucky isolates were sequenced; one collected prior to the epidemic (2004) and one collected during the epidemic (2010). Comparative genomic analysis demonstrated significant polymorphisms between the two strains. PCR primers targeting unique and strain-specific regions were developed, and screening of the archived isolates identified the index case of the asymptomatic S. Kentucky epidemic as a heifer that was raised off-site and transported onto the study farm in 2005. Analysis of isolates collected from all heifers brought onto the farm demonstrated frequent re-introduction of clones of the epidemic strain suggesting transmission of pathogens between farms might occur repeatedly.
authors.affiliation: Environmental Microbial and Food Safety Laboratory,Beltsville Agricultural Research Center,USDA-ARS, Beltsville, MD,USA.
authors.forename: B J
authors.initials: BJ
authors.lastname: Haley
authors.affiliation: Division of Microbiology,Center for Food Safety and Nutrition,Food and Drug Administration, College Park, MD,USA.
authors.forename: M
authors.initials: M
authors.lastname: Allard
authors.affiliation: Division of Microbiology,Center for Food Safety and Nutrition,Food and Drug Administration, College Park, MD,USA.
authors.forename: E
authors.initials: E
authors.lastname: Brown
authors.affiliation: Animal Diagnostic Laboratory,Pennsylvania State University,University Park, PA,USA.
authors.forename: E
authors.initials: E
authors.lastname: Hovingh
authors.affiliation: Environmental Microbial and Food Safety Laboratory,Beltsville Agricultural Research Center,USDA-ARS, Beltsville, MD,USA.
authors.forename: J S
authors.initials: JS
authors.lastname: Karns
authors.affiliation: Division of Microbiology,Center for Food Safety and Nutrition,Food and Drug Administration, College Park, MD,USA.
authors.forename: J S
authors.initials: JS
authors.lastname: van Kessel
mesh_terms: D000818:Animals; D058345:Asymptomatic Infections / Q000453:epidemiology*; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology* / Q000382:microbiology; D003612:Dairying; D058872:Epidemics / Q000662:veterinary*; D005260:Female; D016680:Genome, Bacterial / Q000235:genetics; D006801:Humans; D017720:Molecular Epidemiology / Q000379:methods; D016133:Polymerase Chain Reaction / Q000662:veterinary; D011110:Polymorphism, Genetic / Q000235:genetics; D012481:Salmonella Infections, Animal / Q000453:epidemiology* / Q000235:genetics / Q000382:microbiology; D019779:Salmonella enterica / Q000235:genetics; D014481:United States / Q000453:epidemiology
keywords: Salmonella