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The discovery of Helicobacter pylori in 1982 increased interest in the range of other spiral bacteria that had been seen not only in the stomach but also in the lower bowel of many animal species.1 ,2 The power of technologies such as the polymerase chain reaction with genus specific primers revealed that many of these bacteria belong to the genusHelicobacter. These non-pylori helicobacters are increasingly being found in human clinical specimens. The purpose of this article is to introduce these microorganisms to the clinician, put them in an ecological perspective, and to reflect on their likely importance as human pathogens.
Gastric bacteria
In 1987, Dent et al described the presence of a novel bacterium in 3/1300 gastric biopsies.3The initial differentiation was based on morphology, the bacterium having a larger tight helical shape compared to the S shape ofH pylori (fig 1). Subsequent studies have shown that while rarely found in humans it is the dominant gastric organism in a number of animal species including primates, pigs, cats, and dogs.4 Although first given the nameGastrospirillum hominis this gastric bacterium has subsequently been shown to belong to theHelicobacter genus and has been given the provisional name of Helicobacter heilmannii.5 ,6 Another bacterium, Helicobacter felis, which is morphologically similar to H heilmannii by light microscopy, has also been noted in three cases.7-9Its identification is based on the presence of periplasmic fibres which are only visible by electron microscopy. H felis has been used extensively in mouse models ofH pyloriinfection.10
Light micrographs of gastric tissue from humans infected with (A) H pylori and (C) H heilmannii (× 1000). Insets show higher magnifications in which the characteristic S-shape morphology of H pylori (B) can be seen in comparison …