Characterization of the emerging zoonotic pathogen Arcobacter thereius by whole genome sequencing and comparative genomics.

Four Arcobacter species have been associated with human disease, and based on current knowledge, these Gram negative bacteria are considered as potential food and waterborne zoonotic pathogens. At present, only the genome of the species Arcobacter butzleri has been analysed, and still little is known about their physiology and genetics. The species Arcobacter thereius has first been isolated from tissue of aborted piglets, duck and pig faeces, and recently from stool of human patients with enteritis. In the present study, the complete genome and analysis of the A. thereius type strain LMG24486T, as well as the comparative genome analysis with 8 other A. thereius strains are presented. Genome analysis revealed metabolic pathways for the utilization of amino acids, which represent the main source of energy, together with the presence of genes encoding for respiration-associated and chemotaxis proteins. Comparative genome analysis with the A. butzleri type strain RM4018 revealed a large correlation, though also unique features. Furthermore, in silico DDH and ANI based analysis of the nine A. thereius strains disclosed clustering into two closely related genotypes. No discriminatory differences in genome content nor phenotypic behaviour were detected, though recently the species Arcobacter porcinus was proposed to encompass part of the formerly identified Arcobacter thereius strains. The report of the presence of virulence associated genes in A. thereius, the presence of antibiotic resistance genes, verified by in vitro susceptibility testing, as well as other pathogenic related relevant features, support the classification of A. thereius as an emerging pathogen.