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

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Abstract
Background. Our goal was to test the idea that Helicobacter pylori genotypes vary from one population to another. Methods. Analysis of Sau3A and Hinf I restriction fragment–length polymorphism (RFLP) in a 375-bp polymerase chain reaction amplicon of hpaA was used to compare 31 H. pylori isolates from a relatively small and genetically homogeneous population (Goteborg, Sweden) with those of large, genetically heterogeneous populations located in two different countries (50 isolates from Houston, TX, and 69 isolates from Minas Gerais, a state in the southeastern region of Brazil). Results. Five different Sau3A and three different Hinf I restriction patterns were found; different combinations of these comprise 10 different RFLP types, I through X. The RFLP types found in the United States and Brazil collections were very similar, except for two Brazil isolates belonging to type VIII and five Brazil isolates belonging to type X, neither type found in the United States. The overall profile of H. pylori isolates from Sweden was remarkably different, with 18 of 31 (58%) having a new Sau3A restriction pattern, termed gS; 10 of these 18 isolates had Hinf I restriction pattern E (RFLP type VIII), and 8 had Hinf I 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 DNA fragment of H. pylori hpaA revealed that H. pylori genotypes can and do vary from one population to another. We conclude that the unique RFLP profile shown by the group of H. pylori isolates from Goteborg is the result of a cohort effect in this relatively small, stable, genetically homogeneous population. Also, the overall similarity between RFLP profiles of the H. pylori isolates from Texas and Minas Gerais coincides with the fact that although geographically distanced, these populations are similar in being large, dynamic, and genetically heterogeneous.