Comparing chemiluminescent response and intracellular bactericidal activity of bovine blood neutrophils and monocytes against Salmonella Dublin and Escherichia coli

Chemiluminescent (CL) response and the intracellular killing activity of polymorphonuclear neutrophils (PMNs) and monocytes (MOs) from healthy calves were evaluated to clarify the responsiveness of phagocytes to Salmonella Dublin (S. Dublin) and Escherichia coli (E. coli). CL responses of PMNs and MOs against S. Dublin and E. coli were significantly lower (P < 0.05) than that with opsonized zymosan. The intracellular bactericidal activity of PMNs and MOs was found to be effective against E. coli but not against S. Dublin. These findings indicated that the bactericidal activity of bovine PMNs and MOs against S. Dublin was impaired in innate immune response and that a decreased killing activity against S. Dublin could be a contributing factor for chronic salmonellosis in cattle.