Campylobacter geochelonis sp. nov. isolated from the western Hermann’s tortoise (Testudo hermanni hermanni).

During a screening study to determine the presence of Campylobacter spp. in reptiles, three putative strains (RC7, RC11, and RC20) were isolated from different individuals of the western Hermann’s tortoise (Testudo hermanni hermanni). Initially, these isolates were characterized as C. fetus subsp. fetus by multiplex PCR and partial 16S rRNA gene sequence analysis. Further whole genome characterization revealed considerable differences compared to other Campylobacter species. A polyphasic study was then undertaken to determine the exact taxonomic position of the isolates. The three strains were characterized by conventional phenotypic tests and whole-genome sequencing. We generated robust phylogenies that showed a distinct clade containing only these strains using the 16S rRNA and atpA genes and a set of 40 universal proteins. Our phylogenetic analysis demonstrates their designation as a new species and this was further confirmed using whole genome average nucleotide identity within the Campylobacter genus (~80%). Compared to most Campylobacter species, these strains hydrolysed hippurate, grew well at 25 °C but not at 42 °C. Phenotypic and genetic analyses demonstrate that the three Campylobacter strains isolated from the western Hermann’s tortoise represent a novel species within the Campylobacter genus, for which the name Campylobacter geochelonis sp. nov. is proposed, with RC20T (=DSM 102159T =LMG 29375T) as the type strain.