Genetic diversity of canine gastric helicobacters, Helicobacter bizzozeronii and H. salomonis studied by pulsed-field gel electrophoresis

Genetic diversity of Helicobacter bizzozeronii and H. salomonis, two recently identified canine gastric Helicobacter spp., was studied by pulsed-field gel electrophoresis (PFGE). All 15 Finnish H. bizzozeronii strains collected between 1991 and 1996 from pet dogs produced different PFGE patterns with all restriction endonucleases studied (AscI, ApaI, SpeI, NotI and PacI) suggesting significant genetic diversity. The five independent H. salomonis strains produced four different patterns with these enzymes; two strains showed identical patterns with all the enzymes. Three separate isolates from one dog had identical patterns, suggesting long-lasting infection with the same strain. H. salomonis strains had several small fragments common for all strains, suggesting relatedness. The PFGE method was shown to be useful for epidemiological studies of canine gastric helicobacter infection. Hybridisation of the DNA digests with digoxigeninlabelled ureE or 16S rRNA gene probes generated by PCR indicated conservation in the localisation of these genes in the H. salomonis genome, because the probes hybridised with similar size fragments of different strains. In contrast, the probes hybridised with different size fragments of H. bizzozeronii strains. Comparison of Southern blots of PFGE patterns digested with SpeI, ApaI and AscI indicated that each species has two 16S rRNA genes and one urease gene. Genome sizes of 11 H. bizzozeronii strains estimated from SpeI and NotI patterns were c. 1.6-1.9 Mb and those of five H. salomonis strains estimated from NotI and PacI patterns were c. 1.7-1.8 Mb.