Influence of a proton pump inhibitor-based therapy on Helicobacter pylori strain selection

Relationship between the cagA 3' repeat region of Helicobacter pylori, gastric histology, and susceptibility to low pH

BACKGROUND & AIMS

The variation in size of Helicobacter pylori CagA is related to repeat sequences in the 3' region of the cagA gene. We investigated whether structural subtypes of the cagA 3' region are associated with presentation of the infection or to susceptibility to acid.

METHODS

We examined 319 cagA-positive H. pylori isolates: 84 isolates from Bogota, Colombia; 83 from Houston, Texas; 24 from Siena, Italy; and 128 from Seoul, Korea. The cagA 3' region was amplified by polymerase chain reaction. Gastric histology and susceptibility to pH 3 were evaluated in relation to the number of cagA repeat regions.

RESULTS

Strains with more than three repeat regions were associated with significantly higher scores for gastric mucosal atrophy and intestinal metaplasia than those with fewer repeat regions. H. pylori strains with three repeat regions were also significantly more susceptible to pH 3 than isolates with fewer repeat regions.

CONCLUSIONS

H. pylori strains with more than three repeat regions in the 3' region of the cagA gene are associated with enhanced histological injury and with reduced survival in acidic conditions. It is hypothesized that these variants arise within the stomach.

RFLP and RAPD analysis of in vivo genetic interactions between strains of Helicobacter pylori

BACKGROUND

The nature of the in vivo interactions between co-colonizing strains of Helicobacter pylori has not been well studied. This study was designed to investigate the in vivo interaction between strains of H. pylori using restriction fragment length polymorphism analysis (RFLP) and random amplified polymorphic DNA fingerprinting (RAPD) analysis.

MATERIALS AND METHODS

Mice were orally inoculated with either a single strain or a mixture of strains, and killed at various time intervals up to 12 months after inoculation.

RESULTS

Inoculum and recovered bacteria were identified by RAPD and RFLP. After 12 months of colonization, bacteria recovered from mice given a single strain were identical to the inoculum. In contrast, bacteria recovered from mice given a mixture of strains developed minor but consistent differences in their RAPD patterns. This variation occurred in spite of the fact that only single strains were recovered from mice given a mixture of strains.

CONCLUSION

These findings support the development of genetic heterogeneity of H. pylori during long-term colonization either by genetic drift or by in vivo recombination. Such genomic modification in vivo could explain the naturally occurring heterogeneity of H. pylori.