Distinction of gastric Helicobacter spp. in humans and domestic pets by scanning electron microscopy

Background. A number of different Helicobacter spp. can colonize the stomac h of humans and domestic pets. Difficulties encountered with primary isolat ion of these spiral microorganisms and their unusual inertia with respect t o biochemical reactions still represent considerable obstacles to their cha racterization with classic tools. In addition, the high degree of similarit y in the 16S rRNA sequence hampers differentiation of Helicobacter spp. usi ng routine molecular biological assays. Materials and Methods. Samples from experimentally monoinfected mice, of na turally infected hosts, and of cultured strains were examined by scanning e lectron microscopy (SEM). In parallel, all samples were analyzed by molecul ar techniques to ascertain the Helicobacter spp. involved. Results. Using the mouse samples as a reference, microorganisms found in na turally infected hosts were identified by SEM as belonging to H. pylori, H. felis, or a group consisting of H. bizzozeronii and H. heilmannii. A furth er spiral microorganism with unique morphology was found in a dog that was positive for H. salomonis, but the organism could not be recovered from exp erimentally infected mice. In culture, most Helicobacter strains lost their ultrastructural characteristics. Conclusions. When gastric Helicobacter spp. were collected from their natur al habitat and examined by SEM, relevant differences could be detected betw een H. felis, H. bizzozeronii and H. heilmannii, and H. salomonis, respecti vely. SEM, therefore, seems to be a useful auxiliary tool for the distincti on of various gastric Helicobacter spp. as based on their ultrastructure.