title: Only one of the two type VI secretion systems encoded in the Salmonella enterica serotype Dublin genome is involved in colonization of the avian and murine hosts.
abstract: The type VI secretion system (T6SS) is a virulence factor for many Gram-negative bacteria. Salmonella genus harbors five phylogenetically distinct T6SS loci encoded in Salmonella Pathogenicity Islands (SPIs) SPI-6, SPI-19, SPI-20, SPI-21 and SPI-22, which are differentially distributed among serotypes. The T6SSs encoded in SPI-6 and SPI-19 contribute to pathogenesis of serotypes Typhimurium and Gallinarum in mice and chickens, respectively. Salmonella Dublin is a pathogen restricted to cattle where it causes a systemic disease. Also, it can colonize other hosts such as chickens and mice, which can act as reservoirs of this serotype. Salmonella Dublin harbors the genes for both T6SS(SPI-6) and T6SS(SPI-19). This study has determined the contribution of T6SS(SPI-6) and T6SS(SPI-19) to host-colonization by Salmonella Dublin using avian and murine models of infection. Competitive index experiments showed that, a mutant strain lacking both T6SSs (∆T6SS(SPI-6)/∆T6SS(SPI-19)) presents a strong colonization defect in cecum of chickens, similar to the defect observed for the ∆T6SS(SPI-6) mutant, suggesting that this serotype requires a functional T6SS(SPI-6) for efficient colonization of the avian gastrointestinal tract. Colonization of mice was also defective, although to a lesser extent than in chickens. In contrast, the T6SS(SPI-19) was not necessary for colonization of either chickens or mice. Transfer of T6SS(SPI-6), but not T6SS(SPI-19), restored the ability of the double mutant to colonize both animal hosts. Our data indicate that Salmonella Dublin requires only the T6SS(SPI-6) for efficient colonization of mice and chickens, and that the T6SS(SPI-6) and T6SS(SPI-19) are not functionally redundant.
authors.forename: David
authors.initials: D
authors.lastname: Pezoa
authors.forename: Carlos J
authors.initials: CJ
authors.lastname: Blondel
authors.forename: Cecilia A
authors.initials: CA
authors.lastname: Silva
authors.forename: Hee-Jeong
authors.initials: HJ
authors.lastname: Yang
authors.forename: Helene
authors.initials: H
authors.lastname: Andrews-Polymenis
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Santiviago
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santos Dumont 964, Santiago, Chile. icontrer@uchile.cl.
authors.forename: Inés
authors.initials: I
authors.lastname: Contreras
mesh_terms: D000818:Animals; D058947:Bacterial Secretion Systems; D002645:Chickens; D004064:Digestive System / Q000382:microbiology*; D044404:Genomic Islands; D051379:Mice; D009154:Mutation; D019779:Salmonella enterica / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology*; D013154:Spleen / Q000382:microbiology; D037521:Virulence Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D058947:Bacterial Secretion Systems; D037521:Virulence Factors