title: Mechanisms of Klebsiella pneumoniae resistance to complement-mediated killing.
abstract: The different mechanisms of Klebsiella pneumoniae resistance to complement-mediated killing were investigated by using different strains and isogenic mutants previously characterized for their surface components. We found that strains from serotypes whose K antigen masks the lipopolysaccharide (LPS) molecules (such as serotypes K1, K10, and K16) fail to activate complement, while strains with smooth LPS exposed at the cell surface (with or without K antigen) activate complement but are resistant to complement-mediated killing. The reasons for this resistance are that C3b binds far from the cell membrane and that the lytic final complex C5b-9 (membrane attack complex) is not formed. Isogenic rough mutants (K+ or K-) are serum sensitive because they bind C3b close to the cell membrane and the lytic complex (C5b-9) is formed.
authors.affiliation: Departamento de Microbiología, Universidad de Barcelona, Spain.
authors.forename: S
authors.initials: S
authors.lastname: Merino
authors.forename: S
authors.initials: S
authors.lastname: Camprubí
authors.forename: S
authors.initials: S
authors.lastname: Albertí
authors.forename: V J
authors.initials: VJ
authors.lastname: Benedí
authors.forename: J M
authors.initials: JM
authors.lastname: Tomás
mesh_terms: D001770:Blood Bactericidal Activity; D003179:Complement C3b / Q000378:metabolism; D015938:Complement Membrane Attack Complex / Q000378:metabolism; D003165:Complement System Proteins / Q000502:physiology*; D006801:Humans; D007711:Klebsiella pneumoniae / Q000276:immunology*; D008070:Lipopolysaccharides / Q000378:metabolism
chemical_list: D015938:Complement Membrane Attack Complex; D008070:Lipopolysaccharides; D003179:Complement C3b; D003165:Complement System Proteins