Extension of the species Helicobacter bilis to include the reference strains of Helicobacter sp. flexispira taxa 2, 3 and 8 and Finnish canine and feline flexispira strains.

The evolution and taxonomy of enterohepatic Helicobacter species with flexispira morphology were studied by a polyphasic approach including phenotypic characterization, analysis of 16S rRNA and ureB gene sequences and dot-blot DNA-DNA hybridization of whole genomic DNA. In addition, available phylogenetic data on the HSP60 gene were used in the analysis. The study included 14 Finnish canine and feline flexispira strains, the reference strains of Helicobacter sp. flexispira taxa 2, 3 and 8 and Helicobacter bilis ATCC 51630(T). Phenotypically, all canine and feline strains were similar to H. bilis. Analysis of 16S rRNA gene sequences of these strains revealed a similarity of 97-99.5 %. Similarity of ureB nucleotide and amino acid sequences within the studied flexispira group was 97-100 % and 99-100 %, respectively, revealing close relatedness. ureB sequences of Helicobacter hepaticus had only 64-66 % similarity to the flexispira group. The similarity to Helicobacter trogontum was 81.5-82.1 %. High levels of DNA-DNA hybridization between the strains were found in dot-blot tests. Polyphasic analysis of the phenotypic and genotypic characteristics of the Finnish flexispira strains and the reference strains of taxa 2, 3 and 8 showed that they differed from other Helicobacter species and are members of the previously described species H. bilis. In addition, canine strain F56 differed in all phylogenetic analyses from the H. bilis group and probably represents a novel Helicobacter species.