RT Journal Article SR Electronic(1) A1 De Groote, Dominic A1 van Doorn, Leen-Jan A1 Ducatelle, Richard A1 Verschuuren, Anita A1 Haesebrouck, Freddy A1 Quint, Wim G. V. A1 Jalava, Katri A1 Vandamme, PeterYR 1999 T1 ‘Candidatus Helicobacter suis’, a gastric helicobacter from pigs, and its phylogenetic relatedness to other gastrospirilla JF International Journal of Systematic and Evolutionary Microbiology, VO 49 IS 4 SP 1769 OP 1777 DO https://doi.org/10.1099/00207713-49-4-1769 PB Microbiology Society, SN 1466-5034, AB ‘Gastrospirillum suis’ is an uncultured, tightly spiral micro-organism that has been associated with ulcer disease in the stomachs of pigs. It was the purpose of this study to determine the phylogenetic position of ‘G. suis’. Stomachs of five slaughterhouse pigs, originating from different Belgian and Dutch farms, were selected on the basis of the presence of ‘G. suis’-like bacteria, as demonstrated by biochemical, immunohistochemical and electron microscopical data. Bacterial 16S rDNA was amplified by PCR using broadrange primers and five helicobacter-like sequences were determined either by direct or indirect sequence analysis. An inter-sequence homology of 99·7% was observed, suggesting that the sequences originated from strains belonging to a single species. Phylogenetic analysis of the consensus sequence placed the organism within the genus Helicobacter, where it formed a distinct sub-group together with other gastrospirillum-like bacteria (Helicobacter felis, Helicobacter bizzozeronii, Helicobacter salomonis and ‘Helicobacter heilmannii’ types 1 and 2). Diagnostic PCR primers and a probe were developed that differentiated the porcine sequences from all known helicobacters. These results indicate that the porcine sequences represent a single taxon within the genus Helicobacter. The low similarity level towards H. salomonis (96·6%), its closest validly named neighbour, strongly suggests that this taxon is a novel Helicobacter species. In situ hybridization experiments linked the reference sequence to the ‘G. suis’-like bacteria. On the basis of these results, we propose the name ‘Candidatus Helicobacter suis’ for this gastric helicobacter from pigs., UL https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/00207713-49-4-1769