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Table 1 Differences between isolates of Brucella spp. from hooded seals and other marine mammals.

From: A review of Brucella infection in marine mammals, with special emphasis on Brucella pinnipedialis in the hooded seal (Cystophora cristata)

Methods Results Reference
Biotyping and metabolic activity The only Brucella isolate to metabolize urocanic acid. [64]
PFGE The hooded seal isolate lacked a 182 kB fragment and had some minor differences in a 62 kB fragment which was specific for the pinniped strains. [85]
IRS-PCR There were two specific DNA fragments (fragments 2 and 3) present in all isolates from seals, except the hooded seal isolates. These fragments might be part of metabolic genomic islands. Their absence suggests that the hooded seal isolates may be closely related to an unknown ancestor of Brucella spp. [86]
PCR-RFLP studies of DNA polymorphism at the omp2 locus The hooded seal isolate was classified in a separate group. The Alu I restriction pattern of omp2b was identical for all marine mammal isolates except the hooded seal isolate. [62]
VNTR/MLVA Both VNTR and MLVA subclustered the hooded seal isolates in a separate subcluster (C3), within the B. pinnipedialis cluster. [112, 116]
MLSA The hooded seal isolates belonged to ST25, corresponding to the C3 subcluster mentioned above. [112]
Whole genome comparison by Markov chain based methods The hooded seal isolate grouped separately indicating relatively large genomic compositional differences between this isolate and other brucellae. [124]
Pan-genomic analysis The hooded seal isolate differed from all other Brucella spp. in gene content. The hooded seal genome was also the most GC rich of all the analysed genomes, suggesting that the hooded seal isolate might be closely related to an unknown ancestor of Brucella spp. [124]
Experimental infection of human macrophage-like cells in culture The six hooded seal isolates were unable to enter the human macrophage-like cells. [59]