title: Epithelial entry rather than the ensuing systemic immune response determines the pathogenicity of two Salmonella enterica serovar Typhimurium strains in a mouse model.
abstract: Most studies of Salmonella enterica serovar Typhimurium infection focus only on the pathogenicity of one strain. We investigated whether differences in pathogenicity of two wild-type S. Typhimurium strains; DT120 and SL1344, were related to gut invasion or the resulting immune response. Oral administration of a ten-fold lower number of SL1344 (10(6) CFU) as compared to DT120 (10(7) CFU) resulted in higher bacterial counts in liver and lymph nodes, and led to massive neutrophil infiltration of the spleen, while DT120 administration did not. In contrast, administration of the same dose (10(3) CFU) of the two strains intravenously resulted in the same levels of bacteria and neutrophils in spleen and bone marrow. Oral administration of SL1344 led to an increase in neutrophil apoptosis in both spleen and the bone marrow and four out of five mice died before Day 8, while in DT120 mice, no increase in neutrophil apoptosis was observed and all mice survived until Day 8. This study reveals that two wild-type S. Typhimurium strains, despite evoking highly comparable immune responses upon intravenous injection, exhibit diverse pathogenicity in mice and thus suggests that differences in their invasiveness and survival during gut passage determines the success of the ensuing immune response.
authors: Center for Biological Sequence Analysis, Department of Systems Biology, Technical University of Denmark, Building 224, DK-2800 Kgs. Lyngby, Denmark.
authors: Rikke
authors: R
authors: Brandt
authors: Anne
authors: A
authors: Petersen
authors: Susanne
authors: S
authors: Brix
authors: Tine Rask
authors: TR
authors: Licht
authors: Hanne
authors: H
authors: Frøkiær
mesh_terms: D000818:Animals; D017209:Apoptosis; D058491:Bacterial Load; D001853:Bone Marrow / Q000382:microbiology; D054884:Host-Pathogen Interactions; D008099:Liver / Q000382:microbiology; D008198:Lymph Nodes / Q000382:microbiology; D051379:Mice; D009504:Neutrophils / Q000276:immunology; D012481:Salmonella Infections, Animal / Q000276:immunology / Q000382:microbiology* / Q000473:pathology*; D012486:Salmonella typhimurium / Q000276:immunology* / Q000472:pathogenicity*; D013154:Spleen / Q000382:microbiology; D016019:Survival Analysis
keywords: Epithelial entry; Neutrophils; S. Typhimurium