title: Association of LPS chemotype of Mannheimia (Pasteurella) haemolytica A1 with disease virulence in a model of ovine pneumonic pasteurellosis.
abstract: Host responses during pneumonic pasteurellosis were compared in sheep infected with strains of Mannheimia (Pasteurella) haemolytica A1 differing in their O-antigen type. Nine-week-old, specific pathogen-free lambs were infected intratracheally with parainfluenza type 3 virus (10(8) TCID(50)) followed 7 days later by 5-6 x 10(7) CFU of M. haemolytica A1 possessing rough (group R, 6 lambs) or smooth (group S, 6 lambs) lipopolysaccharide, or saline (group C, 4 lambs). Group C lambs remained afebrile with no evidence of endotoxaemia or bacteraemia and biochemical parameters were normal. Group R and group S lambs became febrile within 2-3 h postinfection and the response was higher and more prolonged in group R lambs. Four group R and 2 group S lambs developed clinical pneumonic pasteurellosis within 24-48 h and the severity of disease correlated with episodes of endotoxaemia, bacteraemia and elevated eicosanoid concentrations. At post-mortem, M. haemolytica (10(7)-10(9) CFU/g) was isolated from the lungs of all 6 group R lambs but from only 1 group S lamb. The results indicate an association between the incidence and severity of ovine pneumonic pasteurellosis and LPS chemotype and suggest an important role for LPS chemotype in determining host-species susceptibility to lung infection.
authors.affiliation: Moredun Research Institute, Penicuik, Midlothian, UK. hodgc@mri.sari.ac.uk
authors.forename: J Christopher
authors.initials: JC
authors.lastname: Hodgson
authors.forename: Gordon M
authors.initials: GM
authors.lastname: Moon
authors.forename: Malcolm
authors.initials: M
authors.lastname: Quirie
authors.forename: William
authors.initials: W
authors.lastname: Donachie
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000276:immunology; D066298:In Vitro Techniques; D008070:Lipopolysaccharides / Q000737:chemistry* / Q000145:classification; D008168:Lung / Q000382:microbiology; D008213:Lymphocyte Activation; D016676:Macrophages, Alveolar / Q000187:drug effects / Q000276:immunology; D016978:Mannheimia haemolytica / Q000472:pathogenicity*; D019081:O Antigens / Q000032:analysis; D012766:Pasteurellosis, Pneumonic / Q000276:immunology / Q000382:microbiology*; D012703:Serotyping; D012756:Sheep; D012757:Sheep Diseases / Q000276:immunology / Q000382:microbiology*; D013047:Specific Pathogen-Free Organisms; D014774:Virulence
chemical_list: D000907:Antibodies, Bacterial; D008070:Lipopolysaccharides; D019081:O Antigens