“…When H. pylori strains isolated from unrelated humans are compared, each isolate is genetically unique, with a level of relatedness among most orthologous sequences ranging from about 90 to 99% nucleotide identity (1,4,21,24,42,49). This diversity is the consequence of numerous point mutations, combined with a very high rate of intraspecies genetic recombination (11,24,49,55). In addition, certain genes are present in some H. pylori strains but absent from others (3,6,13,45).…”