title: The frequency and duration of Salmonella-macrophage adhesion events determines infection efficiency.
abstract: Salmonella enterica causes a range of important diseases in humans and a in a variety of animal species. The ability of bacteria to adhere to, invade and survive within host cells plays an important role in the pathogenesis of Salmonella infections. In systemic salmonellosis, macrophages constitute a niche for the proliferation of bacteria within the host organism. Salmonella enterica serovar Typhimurium is flagellated and the frequency with which this bacterium collides with a cell is important for infection efficiency. We investigated how bacterial motility affects infection efficiency, using a combination of population-level macrophage infection experiments and direct imaging of single-cell infection events, comparing wild-type and motility mutants. Non-motile and aflagellate bacterial strains, in contrast to wild-type bacteria, collide less frequently with macrophages, are in contact with the cell for less time and infect less frequently. Run-biased Salmonella also collide less frequently with macrophages but maintain contact with macrophages for a longer period of time than wild-type strains and infect the cells more readily. Our results suggest that uptake of S. Typhimurium by macrophages is dependent upon the duration of contact time of the bacterium with the cell, in addition to the frequency with which the bacteria collide with the cell.
authors.affiliation: Department of Physics, Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge CB3 0HE, UK.
authors.forename: Sarra
authors.initials: S
authors.lastname: Achouri
authors.affiliation: Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 0ES, UK.
authors.forename: John A
authors.initials: JA
authors.lastname: Wright
authors.affiliation: Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK.
authors.forename: Lewis
authors.initials: L
authors.lastname: Evans
authors.affiliation: Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 0ES, UK.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Macleod
authors.affiliation: Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK.
authors.forename: Gillian
authors.initials: G
authors.lastname: Fraser
authors.affiliation: Department of Physics, Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge CB3 0HE, UK pc245@cam.ac.uk.
authors.forename: Pietro
authors.initials: P
authors.lastname: Cicuta
authors.affiliation: Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 0ES, UK ceb27@cam.ac.uk.
authors.forename: Clare E
authors.initials: CE
authors.lastname: Bryant
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion / Q000502:physiology*; D002448:Cell Adhesion / Q000502:physiology*; D002460:Cell Line; D008264:Macrophages / Q000502:physiology*; D051379:Mice; D009068:Movement; D009154:Mutation; D012486:Salmonella typhimurium / Q000502:physiology*
keywords: flagella; macrophage; motility; phagocytosis; salmonella