Effect of repeated in vitro transfer of Pasteurella haemolytica A1 on encapsulation, leukotoxin production, and virulence.

Inflammatory cytokines enhance the interaction of Mannheimia haemolytica leukotoxin with bovine peripheral blood neutrophils in vitro.

Mannheimia (Pasteurella) haemolytica A1 produces several virulence factors that play an important role in the pathogenesis of bovine pneumonic pasteurellosis. Foremost among these is a leukotoxin (LKT) that specifically kills ruminant leukocytes. Recent evidence suggests that M. haemolytica LKT binding to bovine leukocytes is mediated by the beta(2)-integrin CD11a/CD18 (lymphocyte function-asso...

Molecular genetic analysis of virulence in Mannheimia (pasteurella) haemolytica.

Mannheimia haemolytica (previously known as Pasteurella haemolytica) is a weakly hemolytic, gram-negative coccobacillus that is an opportunistic pathogen of cattle, sheep and other ruminants. In stressed, immunocompromised animals, the organism causes a fibrinous, necrotic pneumonia, commonly called "shipping fever". In the United States, economic losses due to shipping fever pneumonia surpass ...

Influence of Pasteurella haemolytica A1 crude leukotoxin on bovine neutrophil chemiluminescence.

Pasteurella haemolytica A1 crude leukotoxin (25%, vol/vol) rapidly diminished the bovine neutrophil chemiluminescence response to opsonized zymosan. This inhibition was neither prevented nor reversed by 75 mM sucrose. Dilute leukotoxin did not directly stimulate neutrophil chemiluminescence nor did it alter the chemiluminescence response of the neutrophils to opsonized zymosan.

Efficacy of recombinant leukotoxin in protection against pneumonic challenge with live Pasteurella haemolytica A1.

The recombinant leukotoxin (rLKT) of the bacterium Pasteurella haemolytica A1 was examined for its ability to protect cattle from experimental challenge with logarithmic-phase P. haemolytica. Six different vaccines were utilized in the experiment: P. haemolytica culture supernatant, P. haemolytica culture supernatant enriched with rLKT, rLKT alone, P. haemolytica culture supernatant enriched wi...

Different Signaling Pathways Elevation in Bovine Alveolar Macrophages by and Endotoxin Induce Intracellular Calcium A1-Derived Leukotoxin Pasteurella haemolytica