title: The Salmonella pathogenicity island 13 contributes to pathogenesis in streptomycin pre-treated mice but not in day-old chickens.
abstract: BACKGROUND
  Salmonella enterica serovar Enteritidis (S. Enteritidis) is a human and animal pathogen that causes gastroenteritis characterized by inflammatory diarrhea and occasionally an invasive systemic infection. Salmonella pathogenicity islands (SPIs) are horizontally acquired genomic segments known to contribute to Salmonella pathogenesis. The objective of the current study was to determine the contribution of SPI-13 to S. Enteritidis pathogenesis.
  
  
  METHODS
  We deleted the entire SPI-13 (∆SPI-13) from the genome of S. Enteritidis CDC_2010K_0968 strain isolated from a human patient during the 2010 egg-associated outbreak in the US. The kinetics of infection of the wild-type parent and the ∆SPI-13 were compared in orally challenged day-old chickens and streptomycin pre-treated mice. The degree of intestinal inflammation and the survival of mutant strain within the avian (HD11) and murine (RAW264.7) macrophages were also determined.
  
  
  RESULTS
  The deletion of the SPI-13 resulted in impaired infection kinetics of S. Enteritidis in streptomycin pre-treated mice which was characterized by significantly lower (P < 0.05) viable counts in the ceca, liver and spleen, impaired ability to induce intestinal inflammation and reduced survival within murine macrophages. Conversely, there were no significant differences in the infection kinetics of ∆SPI-13 in day-old chickens in any of the organs tested and the survival of ∆SPI-13 within chicken macrophages remained unaltered.
  
  
  CONCLUSIONS
  The results of this study show that SPI-13 contributes to the pathogenesis of S. Enteritidis in streptomycin pre-treated mice but not in day-old chickens and raises the possibility that SPI-13 may play a role in pathogenesis and the host adaptation/restriction of Salmonella serovars.
authors.affiliation: Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164-7040 USA.
authors.forename: Jacob R
authors.initials: JR
authors.lastname: Elder
authors.affiliation: Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164-7040 USA.
authors.forename: Kim Lam
authors.initials: KL
authors.lastname: Chiok
authors.affiliation: Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164-7040 USA.
authors.forename: Narayan C
authors.initials: NC
authors.lastname: Paul
authors.affiliation: Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164-7040 USA.
authors.forename: Gary
authors.initials: G
authors.lastname: Haldorson
authors.affiliation: Egg Quality and Safety Research Unit, Agriculture Research Service, United States Department of Agriculture, Athens, GA 30605 USA.
authors.forename: Jean
authors.initials: J
authors.lastname: Guard
authors.affiliation: Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164-7040 USA ; Paul Allen School for Global Animal Health, College of Veterinary Medicine, Washington State University, Pullman, WA 99164-7040 USA.
authors.forename: Devendra H
authors.initials: DH
authors.lastname: Shah
keywords: Chicken; Host-specificity; Pathogenesis; SPI-13; Salmonella; Salmonella Enteritidis; Salmonella pathogenicity island; Streptomycin pre-treated mice