Detection of <i>Renibacterium salmoninarum</i> in salmonid kidney samples: a comparison of results using double‐sandwich ELISA and isolation on selective medium

Abstract

Abstract A total of 1239 kidney samples from four species of salmonid fish, Atlantic salmon, Salmo salar L., brown trout, Salmo trutta L., Arctic charr, Salvelinus alpinus (L.), and rainbow trout, Oncorhynchus mykiss (Walbaum), were screened for Renibacterium 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 seven out of 12 groups tested, all samples were negative in both tests. Positive ELISA results occurred in five groups. Renibacterium salmoninarum was isolated on SKDM from samples in four out of these five groups. The ELISA test gave significantly higher numbers of positive samples in three out of the four groups showing positive results in both tests.