DAO 21:227-231 (1995)  -  doi:10.3354/dao021227

Bacterial species other than Renibacterium salmoninarum cross-react with antisera against R. salmoninarum but are negative for the p57 gene of R. salmoninarum as detected by the polymerase chain reaction (PCR)

Brown LL, Evelyn TPT, Iwama GK, Nelson WS, Levine RP

Genomic DNA was extracted from 4 strains of Carnobacterium piscicola and 2 strains of Corynebacterium aquaticum that had previously been reported to produce a 57 kDa protein that reacted with polyclonal antiserum against Renibacterium salmoninarum. Genomic DNA was also extracted from a Gram-negative bacterium isolated from the kidney tissue of a mature female coho salmon Oncorhynchus kisutch. The bacterium, tentatively identified as Pseudomonas maltophila, cross-reacts with 2 polyclonal antisera, one of which is used in an enzyme-linked immunosorbent assay and the other in a fluorescent antibody test to identify R. salmoninarum. The isolate of P. maltophila, and the Carnobacterium piscicola and Corynebacterium aquaticum strains, were negative by a polymerase chain reaction (PCR) that was designed to amplify a segment of the gene encoding p57, a major protein of R. salmoninarum. These results suggest that although antibodies directed against R. salmoninarum cross-react with antigens of bacterial species other than R. salmoninarum, the cross-reacting antigen(s) is clearly not the same protein, as the non-R. salmoninarum bacteria lacked the gene encoding p57. These findings highlight some of the shortcomings of immunodiagnostic tests for detecting R. salmoninarum and indicate the high degree of specificity associated with a PCR-based diagnostic technique.


PCR . DNA . BKD detection . Salmon eggs . Bacterial disease . Broodstock screening


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