Spiral organisms were isolated from an antral gastric mucosal biopsy specimen from a dyspeptic patient with gastritis, Only corkscrew-shaped organisms resembling "Gastrospirillum hominis" ("Helicobacter heilmannii") but no Helicobacter pylori-like organisms were seen in histological sections. H. pylori was not cultured from specimens from this patient. On the basis of biochemical reactions, morphology, ultrastructure, and 16S DNA sequencing, the isolated "G. hominis" was shown to be a true Helicobacter sp, very similar to Helicobacter felis and the "Gastrospirillum" but was separate from H. pylori, "G. hominis" is a pleomorphic gram-negative corkscrew-shaped, motile rod with 3 to 8 coils and a wavelength of about 1 mu m. In contrast to H. pylori, it has up to 14 sheathed flagellar uni- or bipolar fibrils but no periplasmic fibrils, "G. horninis" grows under microaerobic conditions at 36 and 41 degrees C on 7% lysed, defibrinated horse blood agar plates within 3 to 7 days and can be subcultured under microaerobic but not under anaerobic conditions on media similar to those used for H. pylori and H. felis, The small translucent colonies were, in contrast to those of H. felis, indistinguishable from those of H. pylori, "G. hominis" is, like H. pylori and H. felis, motile, is oxidase, catalase, nitrite, nitrate, and urease positive, and produces alkaline phosphatase and arginine arylamidase, Like H. pylori and H. felis, it is sensitive to cephalothin (30-mu g disc), resistant to nalidixic acid (30-mu g disc), and sensitive to most other antibiotics. The 16S DNA sequence clusters "G. hominis" together with "Gastrospirillum,'' H. felis, Helicobacter bizzozeronii, Helicobacter salmonii, Helicobacter nemestrinae, Helicobacter acinonychis, and H. pylori.
