Detection of Renibacterium salmoninarum in salmonid kidney samples: a comparison of results using double-sandwich ELISA and isolation on selective medium.
A total of 1239 kidney samples from 4 species of salmonid fish, Atlantic salmon, brown trout (Salmo trutta), Arctic charr (Salvelinus alpinus), and rainbow trout were screened for R. salmoninarum using double-sandwich ELISA and bacterial isolation. For bacterial isolation, samples were homogenized, washed, plated onto S-KDM and incubated for 12 weeks. Samples for ELISA were kept frozen until tested. After thawing, 25% homogenates in PBS were heated at 100°C for 15 min in the presence (2.5% v/v) of HemoDe solvent (terpene and butylated hydroxyanisole) and then centrifuged. The supernatant was tested with polyclonal antibodies against whole bacterium in a double-sandwich ELISA. In 7 of 12 groups tested, all samples were negative in both tests. Positive ELISA results occurred in 5 groups. R. salmoninarum was isolated on S-KDM from samples in 4 out of these 5 groups. The ELISA gave significantly higher numbers of positive samples in 3 out of 4 groups showing positive results in both tests.