A comparison of 16S ribosomal DNA sequences from five isolates of Helicobacter pylori.

Other workers have found that clinical isolates of Helicobacter pylori exhibit very extensive DNA sequence polymorphisms when they are examined by ribotyping or some other genomic sequence characterization technique. In fact, it is rare to find similar clones, much less identical ones, among isolates. We found that the levels of divergence between the 16S ribosomal DNA sequences of individual organisms and the consensus sequence of the five isolates which we examined ranged from 0.2 to 0.5%. In contrast, other workers have shown that levels of divergence between the 16S ribosomal DNA sequence of H. pylori and the 16S ribosomal DNA sequences of four other Helicobacter species range from 2.7 to 8.0%. Our results show that the H. pylori 16S ribosomal DNA is not very polymorphic and support the conclusion that H. pylori is a unique species.