Stable amoxicillin resistance in Helicobacter pylori

Alterations in Penicillin-Binding Protein 1A Confer Resistance to β-Lactam Antibiotics in Helicobacter pylori

“…H. pylori strains used in this study were the Amx r Hardenberg strain (27) and the Amx s H. pylori strains 1061 (11), J99 (2), 26695 (25), and SS1 (15). Bacteria were routinely grown on Columbia agar plates (Becton Dickinson, Cockeysville, Md.)…”

“…The first reported amoxicillin-resistant (Amx r ) strains (MIC Ͼ 256 mg/liter) were isolated from dyspeptic patients in Italy and the United States (10), but they all rapidly lost their amoxicillin resistance in vitro (8). Subsequently the isolation of a stable amoxicillin-resistant clinical H. pylori isolate, the Hardenberg strain, from an 82-year-old Dutch dyspeptic patient was reported (27).…”

“…Later a fourth, low-molecular-weight PBP, PBP4, was identified (14), and subsequently five other potential PBPs (13) and an H. pylori-specific ␤-lactamase (19) have been described. Amoxicillin resistance in H. pylori was found not to rely on the acquisition or expression of ␤-lactamase (8,27). The nonstable amoxicillin resistance of H. pylori (8) is probably due to a decreased expression of the penicillin-binding protein PBPD (7).…”

128 Substitutions in Penicillin-Binding Protein 1 in Amoxicillin-Resistant Helicobacter pylori Strains Isolated from Korean Patients

“…Of the amino acid substitutions, Asn562→Tyr mutation which located near the KTG (555 to 557) motif was identically found in all amoxicillin resistant strains and the mutation was also commonly reported in other strains. 11,19,24 The substitution of Ser414→Arg which occurred in the adjacent to SLN (433 to 435) motif was also identically found in all resistance strains. The contribution to resistance phenotype of Ser414→Arg mutation was previously explained by Gerrits et al 11 The fact that the locations of described amino acid substitutions are adjacent to penicillin-binding motifs suggests that the mutations might be a main mechanism of amoxicillin resistance.…”

“…18 The resistance mechanism of H. pylori is explained by mutation of PBPs, unlike other gram-negative bacilli, b-lactamase has not been found in H. pylori. 6,19 The PBPs are enzyme for formation of peptidoglycan layer of bacterial wall and has its enzymatic activity in the C-terminal region. 20 It has been known that PBPs have some well conserved residues which involved in penicillin binding and the mutations which occurred in or around the regions were related with antibiotic resistance.…”