Occurrence and characterization of gastric Helicobacter spp. in naturally infected dogs

Helicobacter-like organisms are frequently observed in the stomach of dogs but the relationship between these microorganisms and gastric pathology has not been clearly established. Different species of helicobacters are known to be present in the canine stomach but their specific prevalence in natur ally infected dogs is unknown. The aims of this study were to isolate and c haracterize helicobacters in canine gastric biopsies, to compare the common ly used tests for the identification of Helicobacter spp. and to determine the occurrence of these species in dogs. Twenty-three out of 25 dogs (92%) were positive for Helicobacter-like organisms in cytological screening. Cul ture was successful from biopsies of 5/25 dogs. The isolates were analyzed by electron microscopy, biochemical and physiological tests, whole protein analysis and 16S rDNA sequencing. Helicobacter felis was identified in four samples and Helicobacter bizzozeronii in one sample. Only the whole protei n analysis in combination with electron microscopy was able to clearly disc riminate the two species. Compared to the high prevalence of Helicobacter-l ike organisms, the occurrence of H. felis and H. bizzozeronii, was low (17 and 4%, respectively). No Flexispira rappini-like organisms or H, salomonis were detected. Electron microscopy revealed that H. bizzozeronii-like micr oorganisms were present in three additional biopsies where we were unable t o culture any Helicobacter-like organisms. These observations indicate that in the stomach of dogs not all helicobacters are culturable. The uncultura ble bacteria appeared to be the prevalent ones and may represent different spiral organisms. The presence of distinct helicobacters with different cha racteristics can reflect different roles in the pathogenesis of canine gast ric disease, (C) 1999 Elsevier Science B.V. All rights reserved.