Association of virulent genotypes and phylogenetic origins of Helicobacter pylori with gastric cancer.

ABSTRACT

OBJECTIVE: To investigate the association between the genotypes, sequence variations and phylogenetic origins of strains of Helicobacter pylori with gastric cancer in Chinese patients. METHODS: Strains of H. pylori were isolated from patients with chronic gastritis and gastric cancer. Genotypes of the cagA and vacA genes were determined using polymerase chain reaction. Sequence analysis was used to detect variations in the 3' and 5' regions of cagA, and to detect known polymorphisms in cagE. A phylogenetic tree was constructed based on the analysis of seven housekeeping genes. RESULTS: A total of 67 strains of H. pylori were analysed. Nearly all strains of H. pylori carried cagA (65/67; 97.0%), an East Asia type of the cagA 3' region (63/65; 96.9%) and the vacA intermediate (i)1 genotype (65/67; 97.0%). None of the H. pylori strains examined had sequence variations in the 5' region of cagA or cagE. Phylogenetic analyses, however, revealed that strains of H. pylori from gastric cancer tended to cluster together. CONCLUSIONS: Virulent strains of H. pylori were highly prevalent, but virulent genotypes of H. pylori associated with gastric cancer were not detected in this geographical region.