Campylobacter californiensis sp. nov., isolated from cattle and feral swine

Nine <i>Campylobacter</i> strains were isolated from cattle and feral swine faeces: three were recovered during a 2007 <i>Campylobacter</i>-associated outbreak linked to a dairy, and the other six were isolated during a 2009-2010 survey of farms and ranches in Central California. The species identification of these strains could not be determined by 16S rRNA gene sequencing but were most similar to <i>Campylobacter concisus</i> and <i>Campylobacter mucosalis</i>. Additional <i>atpA</i> typing indicated that the nine strains composed a discrete novel clade related to <i>C. concisus</i> and <i>C. mucosalis</i>. A polyphasic study was undertaken here to clarify their taxonomic position. Phylogenetic analyses were performed based on 16S rRNA gene sequences and the concatenated sequences of 330 core genes. The core gene analysis placed the nine strains into a clade well separated from the other <i>Campylobacter</i> taxa, indicating that these strains represent a novel <i>Campylobacter</i> species. Pairwise digital DNA-DNA hybridization and average nucleotide identity values between these strains and other campylobacters are lower than 16 and 73%, respectively, further supporting their placement into a novel taxon. Standard phenotypic testing was performed. All strains are microaerobic or anaerobic, motile, Gram-negative, slightly-curved rods that are oxidase positive but catalase negative. Strains can be distinguished from the other catalase-negative <i>Campylobacter</i> species using phenotypic markers such as motility, oxidase activity, cephalothin resistance, hippuricase activity, growth at 30 °C, and α-haemolysis. The data presented here show that these strains represent a novel species within <i>Campylobacter</i>, for which the name <i>Campylobacter californiensis</i> sp. nov. (type strain RM6914^T=LMG 32304^T=CCUG 75329^T) is proposed.