Virulence-associated genotypes of Helicobacter pylori: do they explain the African enigma?

OBJECTIVES: The aim of this study was to compare the distribution of virulence-associated genotypes of Helicobacter pylori in two Colombian populations with contrasting gastric cancer risk but with similar H. pylori infection prevalence.
METHODS: Gastric biopsies were taken from 241 subjects from the high gastric cancer risk area of Pasto and from 93 subjects from the low risk area of Tumaco. Four gastric biopsies from each patient were fixed in 10% buffered formalin for histopathologic analysis, and one was frozen immediately in liquid nitrogen and used for genotyping. CagA and vacA genotypes were determined by multiplex polymerase chain reaction and reverse hybridization on a line probe assay.
RESULTS: In patients from the population with high risk for gastric cancer, statistically significant higher relative frequencies of cagA positive and vacA s1 and ml genotypes were found as compared to the population from the low risk area.
CONCLUSIONS: Although H. pylori infection has been recognized as a cause of gastric cancer in humans, some large populations with high prevalence of infection have low gastric cancer rates. This so-called "African enigma" so far remains unexplained. Our findings suggest that virulence-associated genes of H. pylori may partially explain the African enigma. Other factors, including human genetic polymorphisms and diet, are also suspected to play a major role. Further investigations are needed to test this hypothesis.