Comparative evaluation of bacterial culture and two ELISA techniques for the detection of Renibacterium salmoninarum antigens in salmonid kidney tissues

Abstract

Soluble anbgens from Renibactenum salmoninarum (Rs) incorporated Into ~rnmunostimulating complexes (iscoms) induced polyclonal antibod~es directed to the heat-stable, 57 kDa antlgen complex of Rs The antibodies were used in an enzyme-linhed immunosorbent assay (ELISA) for the detection of Rs antigens in salnlonid h d n e y sanlples The negative-positlve threshold value in the ELlSA was determined to be 0 10 based on the analyses of 408 samples from rainbow trout Oncorhynchus myklss, Arctic char Salvehnus alpinus, Baltic salmon Salmo salar, and brown trout Salmo trutta, all n e g a t ~v e for Rs by bacterial culture The Rs organism was ~solated on select~ve kidney d ~s e a s e medium (SKDM) after up to 12 wk of incubation from 45% of the samples collected from fish farms having enzootic bacterial h d n e y disease (BKD), and f ~o m fish in populat~ons with clin~cal slgns of BKD ( n = 260) Soluble antigens of Rs were detected with the polyclonal ELISA In 50 % of these samples In a comparative evaluat~on of 3 d~agnostic techniques (bacterial culture, the polyclonal ELISA descnbed here, and a commerc~ally available ELISA based on monoclonal antibodies). 167 k ~d n e y samples were individually analyzed The results of the d~agnostic tests (pos~tive or negative) were ~dentical for 95% of the examined samples A higher sensitivity of the polyclonal ELISA when compared with the monoclonal method was indicated in this study KEY WORDS Bacterial kidney disease.