Divergence between the Highly Virulent Zoonotic Pathogen Helicobacter heilmannii and Its Closest Relative, the Low-Virulence “Helicobacter ailurogastricus” sp. nov.
Helicobacter heilmanniinaturally colonizes the stomachs of dogs and cats and has been associated with gastric disorders in humans. Nine felineHelicobacterstrains, classified asH. heilmanniibased onureABand 16S rRNA gene sequences, were divided into a highly virulent and a low-virulence group. The genomes of these strains were sequenced to investigate their phylogenetic relationships, to define their gene content and diversity, and to determine if the differences in pathogenicity were associated with the presence or absence of potential virulence genes. The capacities of these helicobacters to bind to the gastric mucosa were investigated as well. Our analyses revealed that the low-virulence strains do not belong to the speciesH. heilmanniibut to a novel, closely related species for which we propose the nameHelicobacter ailurogastricus. Several homologs ofH. pylorivirulence factors, such as IceA1, HrgA, and jhp0562-like glycosyltransferase, are present inH. heilmanniibut absent inH. ailurogastricus. Both species contain a VacA-like autotransporter, for which the passenger domain is remarkably larger inH. ailurogastricusthan inH. heilmannii. In addition,H. ailurogastricusshows clear differences in binding to the gastric mucosa compared toH. heilmannii. These findings highlight the low-virulence character of this novelHelicobacterspecies.