Helicobacter heilmannii isolated from the gastric mucosa of cats. Helicobacter heilmannii

H. heilmannii (sensu stricto), a zoonotic bacterium that naturally colonizes the stomach of cats and dogs, has been associated with gastric disease in humans. In a previous experimental infection study, using Mongolian gerbils as a surrogate model, variation in colonization capacity and virulence was demonstrated for 9 strains. Each were isolated from the gastric mucosa of cats and classified as H. heilmannii based on ureAB and 16S rRNA gene sequences. To determine if the differences in colonization and virulence were due to the presence of specific virulence factors, whole genome sequencing was applied to these 9 strains. DNA-DNA hybridization (DDH) parameters, estimated in silico by calculating whole-genome distances using the Genome to Genome Distance Calculator tool, yielded a probability via logistic regression of 96.30% that the 5 highly virulent strains, including the H. heilmannii reference strain, belong to the same species. They were hence identified as H. heilmannii. The DDH estimates for the 4 less virulent strains indicated a probability of only 0.01% that these strains belong to the H. heilmannii species. These data support their re-classification as a novel species for which the name H. ailurogastricus sp. nov (of a cat’s stomach) is proposed. The lower colonization capacity of H. ailurogastricus, as previously shown in vivo, was further investigated using in vitro binding assays. A lower binding capacity to human gastric mucins and epithelial cells was shown for H. ailurogastricus compared to H. heilmannii. H. heilmannii harbors some outer membrane proteins that are not present in H. ailurogastricus, but their role in the colonization process is so far unknown. In addition, the Helicobacter iceA gene, which is putatively involved in ulcer formation, was absent in H. ailurogastricus but present in H. heilmannii.