Specific mutations of penicillin-binding protein 1A in 77 clinically acquired amoxicillin-resistant Helicobacter pylori strains in comparison with 77 amoxicillin-susceptible strains

Background: Amoxicillin (Amx) is one of the most important antibiotics for eradication of Helicobacter pylori (H. pylori). Main determinants of genetically stable Amx resistance are mutations in the C-terminus of penicillin-binding protein 1A (pbp1A). However, contribution of individual mutation remains unclear. Methods: 77 Amx-resistant (Amx^R) and 77 Amx-susceptible (Amx^S) H. pylori strains were isolated from gastric tissues, and DNA sequencing was performed to compare C-terminus sequences of pbp1A gene between Amx^R and Amx^S strains. Natural transformation of these mutated genes into amoxicillin-susceptible strains was performed. Results: Among many mutations in pbp1A, D479E (OR: 37.4, 95% CI: 5.53-252.49, P <.001), and T593 mutation (OR: 32.0, 95% CI: 4.04-252.86, P <.001) independently contributed to Amx resistance in H. pylori strains. In the transformation experiment, T593 mutations were identified in their transformants showing Amx resistance. However, PCR product of D479E was not inserted into recipient (ATCC 43504) resulting in transformation failure. Conclusion: Amx resistance is associated with various substitutions in pbp1A and T593 mutation contributes to Amx resistance of H. pylori.