Investigation of factors influencing the ability of Renibacterium salmoninarum to stimulate rainbow trout macrophage respiratory burst activity

The early stages of contact between Renibacterium salmoninarum and rainbow trout macrophages were investigated. Live R. salmoninarum elicited 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 TNFa was used to activate the macrophages prior to contact with R. 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 of R. salmoninarum with serum factors also increased the respiratory burst, but no difference was found between normal serum and heat-inactivated serum.