title: The Salmonella Pathogenicity Island (SPI) 1 contributes more than SPI2 to the colonization of the chicken by Salmonella enterica serovar Typhimurium.
abstract: BACKGROUND
  Salmonella enterica serovar Typhimurium (Typhimurium) is an important pathogen that infects a broad range of hosts. In humans, Typhimurium causes a gastroenteritis characterized by vomiting, diarrhea, and abdominal pains. Typhimurium infection occurs mainly through the ingestion of contaminated food including poultry, pork, eggs, and milk. Chickens that are asymptomatic carriers of Typhimurium constitute a potential reservoir for infection. The type three secretion systems encoded by Salmonella pathogenicity islands (SPI) 1 and 2 are major virulence factors of Salmonella. However, only a few studies have investigated their role during the infection of chickens.
  
  
  RESULTS
  We have taken a mixed infection approach to study the contribution of SPI1 and SPI2 to the colonization of the chicken by Typhimurium. We found that SPI1 contributes to colonization of both the cecum and spleen in the chicken. In contrast, SPI2 contributes to colonization of the spleen but not the cecum and, in the absence of SPI1, inhibits cecal colonization. Additionally, we show that the contribution of SPI1 in the spleen is greater than that of SPI2. These results are different from those observed during the infection of the mouse by Typhimurium where SPI2 is the major player during systemic colonization.
  
  
  CONCLUSIONS
  The co-infection model we used provides a sensitive assay that confirms the role of SPI1 and clarifies the role of SPI2 in the colonization of the chicken by Typhimurium.
authors.affiliation: The Biodesign Institute, Center for Infectious Diseases and Vaccinology, Arizona State University, Tempe, Arizona 85287, USA. Yakhya.Dieye@asu.edu
authors.forename: Yakhya
authors.initials: Y
authors.lastname: Dieye
authors.forename: Keith
authors.initials: K
authors.lastname: Ameiss
authors.forename: Melha
authors.initials: M
authors.lastname: Mellata
authors.forename: Roy
authors.initials: R
authors.lastname: Curtiss
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D002432:Cecum / Q000382:microbiology; D002645:Chickens / Q000382:microbiology*; D003627:Data Interpretation, Statistical; D015964:Gene Expression Regulation, Bacterial; D015723:Gene Library; D044404:Genomic Islands; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D009154:Mutation; D011201:Poultry Diseases / Q000235:genetics; D012481:Salmonella Infections, Animal / Q000235:genetics* / Q000382:microbiology; D012486:Salmonella typhimurium / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity*; D012703:Serotyping; D013154:Spleen / Q000382:microbiology
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; C440638:SPI-2 protein, Salmonella; C419942:Spi1 protein, Salmonella