Multiple amino acid substitutions in penicillin-binding protein-1A confer amoxicillin resistance in refractory Helicobacter pylori infection

Background: Amoxicillin resistance in Helicobacter pylori is mainly associated with mutations in penicillin-binding protein-1A (PBP-1A). However, the specific amino acid substitu-tions in PBP-1A that confer amoxicillin resistance in H. pylori remain to be investigated. Objective: This study aimed to investigate the molecular mechanism underlying amoxicillin resistance in patients with refractory H. pylori infection.Methods: Esophagogastroduodenoscopy (EGD) was performed in patients with persistent H. py-lori infection after at least two courses of H. pylori eradication therapy between January-2018 to March-2021. Refractory H. pylori was cultured from the gastric biopsy specimens. Antibiotic susceptibility testing was conducted to determine the minimum inhibitory concentrations (MICs). Sequence analysis of pbp-1A was performed for amoxicillin-resistant strains. Results: Thirty-nine successfully cultured isolates were classified as refractory H. pylori iso-lates, and seventeen isolates were resistant to amoxicillin (MIC > 0.125 mg/L). Sequence anal-ysis of resistant strains showed multiple mutations in the C-terminal region of PBP-1A that conferred amoxicillin resistance in H. pylori. However, the number of PBP-1A mutations did not correlate with the high MICs of amoxicillin-resistant isolates. Notably, some amino acid substitutions were identified in all Taiwanese isolates with history of eradication failure but not in published amoxicillin-susceptible strains, suggesting that the mutations may play a role in conferring antibiotic resistance to these strains.Conclusions: Our results show that amoxicillin resistance in refractory H. pylori is highly corre-lated with numerous PBP-1A mutations that are strain specific. Continuous improvements in diagnostic tools, particularly molecular analysis approaches, can help to optimize current anti-microbial regimens.Copyright 2022, Taiwan Society of Microbiology. Published by Elsevier Taiwan LLC. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).