Biochemical, serological, and genetic characterisation of Renibacterium salmoninarum isolates recovered from salmonids in Chile

The Gram-positive Renibacterium salmoninarum causes bacterial kidney disease, a serious threat to Chilean salmon farming. To aid in vaccine development, this study used biochemical, antigenic, and genetic techniques to characterise 39 R. salmoninarum isolates from diseased Salmo salar and Oncorhynchus kisutch. Regardless of host, R. salmoninarum isolates were highly homogeneous pheno-typically. However, the isolates presented varied hydrophobicity (10-90%), as found by hydrocarbon adhesions, and distinct siderophores production, as evaluated on chrome azurol S agar. Serological assays established antigenic homogeneity among isolates, which can facilitate vaccine development. While western-blot profiles (using antiserum against iron-limited R. salmoninarum) differed, all isolates belonged to the same serogroup. Finally, RAPD, ERIC-PCR, and REP-PCR supported genetic R. salmoninarum homogeneity, suggesting clonal relationships. In conclusion, high homogeneity might facilitate vaccine development, but in vivo studies are needed to clarify the relationship of R. salmoninarum virulence with hydrophobicity/siderophores synthesis.