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)

摘要

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.