Distribution of distinct vacA, cagA and iceA alleles in Helicobacter pylori in Hong Kong

Abstract

Background: There is a substantial genetic heterogeneity among Helicobacter pylori strains, and certain genotypes have been suggested to be associated with the virulence of this pathogen. The aim of this study was to investigate the distribution of H. pylori vacA, cagA and iceA genotypes and their association with duodenal ulcer disease in Hong Kong.

Materials and methods: Gastric biopsies of 72 H. pylori infected patients were analyzed by specific polymerase chain reactions.

Results: Of the 72 cases, 69 (95.8%) had vacA signal sequence s1c strains, and three (4.2%) had s1a strains. vacA middle region sequences, m1b and m2, were detected in 23 (31.9%) and 46 (63.9%), respectively. Six (8.3%) cases contained multiple vacA subtypes. vacA s2 allele was only observed in three (4.3%) cases, which were also infected with s1c subtype. cagA was present in 64 (88.9%) of 72 patients, and iceA1 subtype was detected in 46 (63.9%) cases. Neither cagA nor vacA and iceA were associated with duodenal ulcer disease.

Conclusion: The distribution of vacA, cagA and iceA alleles in H. pylori strains in Hong Kong is similar to that in east Asia. There is a difference in the distribution of genotypes between strains in Hong Kong and those in mainland China, although strains in the two regions exhibit a very close relation. The association of these virulence genes and duodenal ulcer disease needs reappraisal, particularly under geographic considerations.