Investigation of factors influencing the ability ofRenibacterium salmoninarumto stimulate rainbow trout macrophage respiratory burst activity

The early stages of contact betweenRenibacterium salmoninarumand rainbow trout macrophages were investigated. LiveR. salmoninarumelicited a respiratory burst, which was enhanced by heat-killing the microorganism. This phenomenon, though, was not observed using UV killed bacteria. Both responses were enhanced when a combination of LPS and TNFαwas used to activate the macrophages prior to contact withR. salmoninarum. Further studies demonstrated that both compounds synergised to enhance O2−production, and that this was correlated with the ability to kill the pathogen. Opsonisation ofR. salmoninarumwith serum factors also increased the respiratory burst, but no difference was found between normal serum and heat-inactivated serum.