Abstract
BACKGROUND: Helicobacter pylori (H. pylori) has infected approximately 4.4 billion individuals worldwide. The known virulence genes and the existing H. pylori typing methods have not been shown to have a recognized correlation with its infectivity. The aim of this study was to elucidate the relationships among known important virulence genes, coccoid transformation, and cytotoxicity of H. pylori isolated from individuals with different clinical diseases to provide guidance for the development of new virulence typing methods for H. pylori. METHODS: The known important virulence genes of 35 H. pylori strains were identified by whole-gene next-generation sequencing (WGS) and polymerase chain reaction (PCR). The chronological changes in the proportion of coccoid forms of H. pylori and their ultramicroscopic structures were observed chronologically using transmission electron microscopy. Human gastric mucosal epithelial cells (GES-1) were infected with H. pylori strains in vitro to evaluate cytotoxicity of H. pylori. RESULTS: There were no significant correlations among the known important virulence genes, coccoid transformation and cytotoxicity of H. pylori isolated from patients with different clinical diseases. We developed a new virulence classification based on the defensive and offensive abilities of H. pylori. CONCLUSIONS: Coccoid transformation and virulence are two independent characteristics of H. pylori that reflect its defensive and offensive abilities, respectively. These two abilities work synergistically, warranting the construction of a new virulence typing method for H. pylori. However, the correlation between the new virulence classification and pathogenic ability still needs to be further verified.