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DOI: 10.1177/09680519030090010201 Association of LPS chemotype of Mannheimia (Pasteurella) haemolytica A1 with disease virulence in a model of ovine pneumonic pasteurellosisMoredun Research Institute, Penicuik, Midlothian, UK, hodgc{at}mri.sari.ac.uk
Moredun Research Institute, Penicuik, Midlothian, UK
Moredun Research Institute, Penicuik, Midlothian, UK
Moredun Research Institute, Penicuik, Midlothian, UK 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 (108 TCID50) followed 7 days later by 56 . 107 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 23 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 2448 h and the severity of disease correlated with episodes of endotoxaemia, bacteraemia and elevated eicosanoid concentrations. At postmortem, M. haemolytica (107109 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.
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