Characterization of elongated Helicobacter pylori isolated from a patient with gastric-mucosa-associated lymphoid-tissue lymphoma.

To date, two Helicobacter species, Helicobacter pylori and 'Helicobacter heilmannii' (formerly named 'Gastrospirillum hominis'), have been identified from the human stomach. In this study, we observed non-H. pylori-shaped bacteria in gastric tissue sections and successfully isolated them by cultivation. Elongated bacteria were isolated from a patient with gastric-mucosa-associated lymphoid-tissue lymphoma who had been diagnosed as H. pylori-negative by culture, rapid urease test and histopathology in another hospital. The bacteria were grown only on chocolate agar in a CO2 incubator, appeared more than 10 microm long in histological sections, formed small colonies and showed poor growth in a brain heart infusion broth; these characteristics apparently differed from common clinical isolates of H. pylori. However, the bacteria were identified as H. pylori by PCR of the urease gene, 16S rDNA sequencing, protein profile and antigenicity examined by anti-H. pylori polyclonal antibody. These observations suggest that the H. pylori strain identified in this study may contribute to the development of gastroduodenal diseases in cases judged as H. pylori-negative by ordinary methods.