title: The Salmonella pathogenicity island 1 and Salmonella pathogenicity island 2 type III secretion systems play a major role in pathogenesis of systemic disease and gastrointestinal tract colonization of Salmonella enterica serovar Typhimurium in the chicken.
abstract: Salmonella enterica serovar Typhimurium infection of chickens is a major public and animal health problem. In young chicks, S. Typhimurium infection results in severe systemic infection; in older chicks, infection results in prolonged gastrointestinal tract colonization. Here we determined the role of the Salmonella pathogenicity island 1 (SPI-1) and Salmonella pathogenicity island 2 (SPI-2) type III secretion systems in systemic infection and gastrointestinal tract colonization of the chicken though experimental infection of chicks with a S. Typhimurium strain with mutations in the genes encoding the secretion system machinery of SPI-1 (spaS) and SPI-2 (ssaU) that prevent secretion of effector proteins. In 1-day-old chicks, mutation of SPI-2 lead to a decrease in both systemic bacterial numbers and pathology, although no difference in gastrointestinal numbers was observed. Mutation of SPI-1 had little effect in 1-day old chicks. In 1-week-old animals the SPI-2 mutants could not be detected systemically and colonized the gastrointestinal tract only in low numbers in comparison with the parent strain, and was cleared in 1 week. The SPI-1 mutant showed greatly reduced levels of systemic infection, and colonized the gastrointestinal tract at a lower level than the parent strain. The findings show that the SPI-2 type III secretion system is required for systemic S. Typhimurium infection in both infection models, and that it plays a significant role in gastrointestinal colonization. The SPI-1 system is involved in both systemic infection and gastrointestinal colonization, but does not appear absolutely essential for either infection process.
authors.affiliation: School of Veterinary Medicine and Science, University of Nottingham, Loughborough, UK.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Jones
authors.forename: Scott D
authors.initials: SD
authors.lastname: Hulme
authors.forename: Paul A
authors.initials: PA
authors.lastname: Barrow
authors.forename: Paul
authors.initials: P
authors.lastname: Wigley
mesh_terms: D000375:Aging; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002353:Carrier State / Q000662:veterinary; D002645:Chickens / Q000382:microbiology*; D015964:Gene Expression Regulation, Bacterial; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D011201:Poultry Diseases / Q000382:microbiology*; D012481:Salmonella Infections, Animal / Q000382:microbiology*; D012486:Salmonella typhimurium / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity*
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; C440638:SPI-2 protein, Salmonella; C419942:Spi1 protein, Salmonella