title: Non-typhoidal Salmonella Typhimurium ST313 isolates that cause bacteremia in humans stimulate less inflammasome activation than ST19 isolates associated with gastroenteritis.
abstract: Salmonella is an enteric pathogen that causes a range of diseases in humans. Non-typhoidal Salmonella (NTS) serovars such as Salmonella enterica serovar Typhimurium generally cause a self-limiting gastroenteritis whereas typhoidal serovars cause a systemic disease, typhoid fever. However, S. Typhimurium isolates within the multi-locus sequence type ST313 have emerged in sub-Saharan Africa as a major cause of bacteremia in humans. The S. Typhimurium ST313 lineage is phylogenetically distinct from classical S. Typhimurium lineages, such as ST19, that cause zoonotic gastroenteritis worldwide. Previous studies have shown that the ST313 lineage has undergone genome degradation when compared to the ST19 lineage, similar to that observed for typhoidal serovars. Currently, little is known about phenotypic differences between ST313 isolates and other NTS isolates. We find that representative ST313 isolates invade non-phagocytic cells less efficiently than the classical ST19 isolates that are more commonly associated with gastroenteritis. In addition, ST313 isolates induce less Caspase-1-dependent macrophage death and IL-1β release than ST19 isolates. ST313 isolates also express relatively lower levels of mRNA of the genes encoding the SPI-1 effector sopE2 and the flagellin, fliC, providing possible explanations for the decrease in invasion and inflammasome activation. The ST313 isolates have invasion and inflammatory phenotypes that are intermediate; more invasive and inflammatory than Salmonella enterica serovar Typhi and less than ST19 isolates associated with gastroenteritis. This suggests that both phenotypically and at the genomic level ST313 isolates are evolving signatures that facilitate a systemic lifestyle in humans.
authors: Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305, USA.
authors: Sarah
authors: S
authors: Carden
authors: Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK.
authors: Chinyere
authors: C
authors: Okoro
authors: Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK.
authors: Gordon
authors: G
authors: Dougan
authors: Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305, USA dmonack@stanford.edu.
authors: Denise
authors: D
authors: Monack
mesh_terms: D017954:Africa South of the Sahara; D016470:Bacteremia / Q000382:microbiology / Q000473:pathology*; D005759:Gastroenteritis / Q000382:microbiology / Q000473:pathology*; D006801:Humans; D058847:Inflammasomes / Q000378:metabolism*; D012480:Salmonella Infections / Q000382:microbiology / Q000473:pathology*; D012486:Salmonella typhimurium / Q000276:immunology*
chemical_list: D058847:Inflammasomes
keywords: genomic degradation; iNTS; immune evasion