Genomic fingerprinting and development of a dendrogram for Brucella spp. isolated from seals, porpoises, and dolphins

Genomic DNA from reference strains and biovars of the genus Brucella was an alyzed using pulsed-field gel electrophoresis (PFGE). Fingerprints were com pared to estimate genetic relatedness among the strains and to obtain infor mation on evolutionary relationships. Electrophoresis of DNA digested with the restriction endonuclease XbaI produced fragment profiles for the refere nce type strains that distinguished these strains to the level of species. Included in this study were strains isolated from marine mammals. The PFGE profiles from these strains were compared with those obtained from the refe rence strains and biovars. Isolates from dolphins had similar profiles that were distinct from profiles of Brucella isolates from seals and porpoises. Distance matrix analyses were used to produce a dendrogram Biovars of B. a bortus were clustered together in the dendrogram; similar clusters were sho wn for biovars of B. melitensis and for biovars of B, suis. Brucella ovis, B. canis, and B. neotomae differed from each other and from B. abortus, B. melitensis, and B. suis. The relationship between B. abortus strain RB51 an d other Brucella biovars was compared because this strain has replaced B. a bortus strain 19 for use as a live vaccine in cattle and possibly in bison and elk. These results support the current taxonomy of Brucella species and the designation of an additional genomic group(s) of Brucella. The PFGE an alysis in conjunction with distance matrix analysis was a useful tool for c alculating genetic relatedness among the Brucella species.