Differences among Helicobacter pylori strains isolated from three different populations and demonstrated by restriction enzyme analysis of an internal fragment of the conserved gene hpaA

Background. Our goal was to test the idea that Helicobacter pylori genotype s vary from one population to another. Methods. Analysis of Sau3A and HinfI restriction fragment-length polymorphi sm (RFLP) in a 375-bp polymerase chain reaction amplicon of hpaA was used t o compare 31 H. pylori isolates from a relatively small and genetically hom ogeneous population (Goteborg, Sweden) with those of large, genetically het erogeneous populations located in two different countries (50 isolates from Houston, TX, and 69 isolates from Minas Gerais, a state in the southeaster n region of Brazil). Results. Five different Sau3A and three different HinfI restriction pattern s were found; different combinations of these comprise 10 different RFLP ty pes, I through X. The RFLP types found in the United States and Brazil coll ections were very similar, except for two Brazil isolates belonging to type VIII and five Brazil isolates belonging to type X, neither type found in t he United States. The overall profile of H. pylori isolates from Sweden was remarkably different, with 18 of 31 (58%) having a new Sau3A restriction p attern, termed gS; 10 of these 18 isolates had HinfI restriction pattern E (RFLP type VIII), and 8 had HinfI restriction pattern F (RFLP type IX). No isolates from Sweden belonged to RFLP type III or type X. Conclusions. RFLP typing of a 375-bp polymerase chain reaction-amplified DN A fragment of H. pylori hpaA revealed that H. pylori genotypes can and do v ary from one population to another. We conclude that the unique RFLP profil e shown by the group of H. pylori isolates from Goteborg is the result of a cohort effect in this relatively small, stable, genetically homogeneous po pulation. Also, the overall similarity between RFLP profiles of the H. pylo ri isolates from Texas and Minas Gerais coincides with the fact that althou gh geographically distanced, these populations are similar in being large, dynamic, and genetically heterogeneous.