A COMPARISON OF 16S RIBOSOMAL DNA-SEQUENCES FROM 5 ISOLATES OF HELICOBACTER-PYLORI

Other workers have found that clinical isolates of Helicobacter pylori exhibit very extensive DNA sequence polymorphisms when they are exami ned by ribotyping or some other genomic sequence characterization tech nique. 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 consen sus 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 168 ribosomal DNA sequence of H. pylori and the 168 ribos omal DNA sequences of four other Helicobacter species range from 2.7 t o 8.0%. Our results show that the H. pylori 16S ribosomal DNA is not v ery polymorphic and support the conclusion that H. pylori is a unique species.