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

A number of different Helicobacter spp. can colonize the stomach of humans and domestic pets. Difficulties encountered with primary isolation of these spiral microorganisms and their unusual inertia with respect to biochemical reactions still represent considerable obstacles to their characterization with classic tools. In addition, the high degree of similarity in the 16S rRNA sequence hampers differentiation of Helicobacter spp. using routine molecular biological assays.

Samples from experimentally monoinfected mice, of naturally infected hosts, and of cultured strains were examined by scanning electron microscopy (SEM). In parallel, all samples were analyzed by molecular techniques to ascertain the Helicobacter spp. involved.

Using the mouse samples as a reference, microorganisms found in naturally infected hosts were identified by SEM as belonging to H. pylori, H. felis, or a group consisting of H. bizzozeronii and H. heilmannii. A further spiral microorganism with unique morphology was found in a dog that was positive for H. salomonis, but the organism could not be recovered from experimentally infected mice. In culture, most Helicobacter strains lost their ultrastructural characteristics.

When gastric Helicobacter spp. were collected from their natural habitat and examined by SEM, relevant differences could be detected between H. felis, H. bizzozeronii and H. heilmannii, and H. salomonis, respectively. SEM, therefore, seems to be a useful auxillary tool for the distinction of various gastric Helicobacter spp. as based on their ultrastructure.