Campylobacter australis sp. nov. isolated from the oral mucosa of sheep

The genus Campylobacter includes enteropathogenic species with a significant impact on human and animal health. Most of the currently available data on this genus are from strains obtained from faecal samples. However, several species have been identified through the analysis of non-faecal samples, including those from the oral mucosa. In the present study, the characterization of three strains representing a novel taxon isolated from the oral mucosa of sheep is described. The strains were characterized by using a polyphasic taxonomic approach, including multiple techniques for phenotypic characterization, with cell morphology, growth characteristics, biochemical tests and genomic features. Phenotypic characterization revealed that the isolated strains are microaerophilic, Gram-negative, curved bacilli with a polar flagellum, catalase-positive and oxidase-negative. Phylogenetic analyses based on the 16S rRNA and hsp60 genes, together with a core genome phylogeny, grouped the strains into a distinct clade separate from previously described Campylobacter species, with Campylobacter suis as the closest Campylobacter species (99.4–99.5% 16S rRNA gene sequence similarity), thereby clarifying their taxonomic position. These findings were supported by in silico analyses, including digital DNA–DNA hybridization and average nucleotide identity, with values of 49.2 and 92.4%, respectively, both below the accepted species thresholds. The draft genome sequence of the type strain M4 T comprises ~1.8 Mb, and the DNA G+C content is 36.5 mol%. On the basis of these results, it was revealed that the new strains obtained from the oral mucosa of sheep represent a novel species of the genus Campylobacter , for which we propose the name Campylobacter australis sp. nov. with M4 T (=LMG 33826 T =CCUG 78219 T ) designated as the type strain.