Genetic and phenotype changes following in vitro interactions between Helicobacter pylori strains

Document Type



Medicine; Gastroenterology


Background:  The purpose of the present paper was to determine whether in vitro interaction between different Helicobacter pylori strains leads to changes in antibiotic susceptibility, cagA, vacAM2 and DNA fingerprint patterns.

Methods:  Three H. pylori strains with known antibiotic susceptibility, cagA, vacAM2 status and polymerase chain reaction–random amplified polymorphic DNA (PCR-RAPD) fingerprint analysis were suspended in phosphate buffered saline (PBS pH 7.0), and the suspensions were mixed in equal proportion prior to culture on chocolate agar plates. Subcultures were performed five times every 3 days. As a control, each of the three strains was also subcultured separately. Antibiotic susceptibility testing, PCR for cagA, vacAM2 and PCR-RAPD analysis were done.

Results:  Surviving strain of the two H. pylori strains in each combination demonstrated change in resistance to both antibiotics but no change in sensitivity. CagA status of the surviving strain varied as compared to the vacAM2 status, which did not change. The PCR-RAPD fingerprint showed unique band pattern.

Conclusion:  DNA transformation follows in vitro interaction. Helicobacter pylori strain with antibiotic resistance is likely to dominate in such in vitro interactions between various strains.