Arcobacter trophiarum sp. nov., isolated from fattening pigs

In the course of a longitudinal study elucidating the dynamics of Arcobacter populations in pigs, 16 isolates of Gram-reaction-negative, rod-shaped, slightly curved, non-spore-forming bacteria were grouped by amplified fragment length polymorphism analysis into a distinct phenon within the genus Arcobacter. Fragments were generated for all isolates in a genus-specific PCR assay, but no amplicon was obtained in a species-specific multiplex-PCR test. Numerical analysis of the whole-cell protein profiles also showed that all isolates clustered in a single group that was distinct from related members of the genus Arcobacter. DNA-DNA hybridizations between two representative strains, designated 64(T) and 122, of the isolates obtained exhibited a mean DNA-DNA relatedness of 72 %. DNA-DNA hybridizations between strains 64(T) and 122 and reference strains of other animal-related bacteria of the genus Arcobacter revealed binding values of 47 % or less. The DNA G+C contents of the two representative strains were 28.5 and 28.4 mol%, respectively, and analysis of three marker genes identified Arcobacter cryaerophilus, A. thereius, A. cibarius and A. skirrowii as their closest phylogenetic neighbours. Strains 64(T) and 122 could be distinguished from other members of the genus Arcobacter by means of biochemical tests for catalase and urease activities, nitrate reduction, indoxyl acetate hydrolysis, lack of growth at 37 °C, growth in 2 % (w/v) NaCl, growth on 0.1 % sodium deoxycholate and non-supplemented Campylobacter charcoal-deoxycholate base medium and resistance to cephalothin (32 mg l(-1)) and cefoperazone (64 mg l(-1)). Additionally, a PCR assay was developed for the detection and identification of strains 64(T) and 122, which represent a novel species of the genus Arcobacter, for which the name Arcobacter trophiarum sp. nov. is proposed. The type strain is strain 64(T) (=LMG 25534(T) =CCUG 59229(T)).