title: Aeromonas salmonicida grown in vivo.
abstract: The virulent fish pathogen Aeromonas salmonicida was rapidly killed in vivo when restricted inside a diffusion chamber implanted intraperitoneally in rainbow trout. After a period of regrowth, the survivors had acquired resistance to host-mediated bacteriolysis, phagocytosis, and oxidative killing, properties which were subsequently lost by growth in vitro. Resistance to bacteriolysis and phagocytosis was associated with a newly acquired capsular layer revealed by acidic polysaccharide staining and electron microscopy. This capsular layer shielded the underlying, regular surface array (S-layer) from immunogold labeling with a primary antibody to the S-layer protein. Resistance to oxidative killing was mediated by a mechanism not associated with the presence of the capsular layer. An attenuated vaccine strain of A. salmonicida grown in vivo failed to express the capsular layer. Consequently, the in vivo-grown cells of this attenuated strain remained as sensitive to bacteriolysis, and as avidly adherent to macrophages, as the in vitro-grown cells. The importance of these new virulence determinants and their relation to the known virulence factors of A. salmonicida are discussed.
authors.affiliation: Department of Biochemistry and Microbiology, University of Victoria, British Columbia, Canada.
authors.forename: R A
authors.initials: RA
authors.lastname: Garduño
authors.forename: J C
authors.initials: JC
authors.lastname: Thornton
authors.forename: W W
authors.initials: WW
authors.lastname: Kay
mesh_terms: D000333:Aeromonas / Q000254:growth & development* / Q000472:pathogenicity / Q000502:physiology / Q000648:ultrastructure; D000818:Animals; D001422:Bacterial Adhesion; D016667:Bacterial Capsules / Q000032:analysis; D015194:Diffusion Chambers, Culture; D007150:Immunohistochemistry; D008264:Macrophages / Q000382:microbiology; D008854:Microscopy, Electron; D014337:Trout; D014774:Virulence