Comparison of Methods Used to Detect Renibacterium salmoninarum,the Causative Agent of Bacterial Kidney Disease

Abstract

Various diagnostic methods used to detect Renibacterum salmoninarum, the causative agent of bacterial kidney disease (BKD), were compared. The most sensitive method was the enzyme immunoassay (the indirect dot blot assay), which could detect 10² bacterial cells per gram of kidney tissue. The minimum bacteria concentrations showing positive reactions to the indirect fluorescent antibody test (IFAT) and the coagglutination test were 10³ and 10⁴ cells/g kidney, respectively. The sensitivities of the Gram stain, immunodiffusion procedure, and latex agglutination test were low, and these methods could only be applied to fish with overt BKD symptoms. Altogether, 656 coho salmon Oncorhynchus kisutch were examined for R. salmoninarum antigen with the direct and indirect dot blot assays (DDBA and IDBA) and the IFAT. Among the fish sampled, positive reactions were obtained in 11.8% by the DDBA, 28.2% by the IDBA, and 12.9% by the IFAT.