Campylobacter canis sp. nov., isolated from the oral cavity of dogs

Some species of the genus Campylobacter have been responsible for several medically important diseases worldwide. Studies of their natural reservoirs have been mainly performed by analysing animal faecal samples. However, other types of samples, such as oral specimens, have been studied very little. In a recent survey of the oral mucosa of domestic dogs without signs of oral or gastrointestinal disease, 14 isolates suspected of belonging to a new Campylobacter species were recovered. A polyphasic study was performed using diverse techniques to assess cell morphology, growth characteristics and genomic content to clarify the taxonomic position of the novel isolates. Phenotypic characterization revealed that the strains isolated from the oral cavity of dogs are microaerophilic, Gram-negative, straight bacilli with a polar flagellum and are positive for catalase and oxidase, but negative for urease. Phylogenetic trees based on 16S rRNA and hsp60 genes grouped them in a distinct clade from the previously described Campylobacter species, with members of the Campylobacter concisus group being the most closely related species (95-98% of 16S rRNA gene sequence similarity). This finding was confirmed through in silico analyses, including digital DNA-DNA hybridization and average nucleotide identity with values <19.6 and <72.6, respectively, with members of the C. concisus group and other valid published Campylobacter species. The type strain MOP7^T draft genome consists of ∼2.1 Mb, and the DNA G+C content is 37.6 mol%. The genetic results and the phenotypic differentiation revealed that the new strains from the oral cavity of dogs correspond to a new species of the genus Campylobacter for which we propose the name Campylobacter canis sp. nov., with MOP7^T (=LMG 33635^T; =CCUG 77916^T) as the type strain.