title: Alterations in penicillin-binding protein 1A confer resistance to beta-lactam antibiotics in Helicobacter pylori.
abstract: Most Helicobacter pylori strains are susceptible to amoxicillin, an important component of combination therapies for H. pylori eradication. The isolation and initial characterization of the first reported stable amoxicillin-resistant clinical H. pylori isolate (the Hardenberg strain) have been published previously, but the underlying resistance mechanism was not described. Here we present evidence that the beta-lactam resistance of the Hardenberg strain results from a single amino acid substitution in HP0597, a penicillin-binding protein 1A (PBP1A) homolog of Escherichia coli. Replacement of the wild-type HP0597 (pbp1A) gene of the amoxicillin-sensitive (Amx(s)) H. pylori strain 1061 by the Hardenberg pbp1A gene resulted in a 100-fold increase in the MIC of amoxicillin. Sequence analysis of pbp1A of the Hardenberg strain, the Amx(s) H. pylori strain 1061, and four amoxicillin-resistant (Amx(r)) 1061 transformants revealed a few amino acid substitutions, of which only a single Ser(414)-->Arg substitution was involved in amoxicillin resistance. Although we cannot exclude that mutations in other genes are required for high-level amoxicillin resistance of the Hardenberg strain, this amino acid substitution in PBP1A resulted in an increased MIC of amoxicillin that was almost identical to that for the original Hardenberg strain.
authors.affiliation: Department of Gastroenterology and Hepatology, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: M M
authors.initials: MM
authors.lastname: Gerrits
authors.forename: D
authors.initials: D
authors.lastname: Schuijffel
authors.forename: A A
authors.initials: AA
authors.lastname: van Zwet
authors.forename: E J
authors.initials: EJ
authors.lastname: Kuipers
authors.forename: C M J E
authors.initials: CM
authors.lastname: Vandenbroucke-Grauls
authors.forename: J G
authors.initials: JG
authors.lastname: Kusters
mesh_terms: D000658:Amoxicillin / Q000494:pharmacology*; D001426:Bacterial Proteins; D002352:Carrier Proteins; D002473:Cell Wall / Q000378:metabolism; D016480:Helicobacter pylori / Q000187:drug effects* / Q000235:genetics; D006602:Hexosyltransferases / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D009097:Multienzyme Complexes / Q000235:genetics*; D002267:Muramoylpentapeptide Carboxypeptidase; D009154:Mutation; D046915:Penicillin-Binding Proteins; D010458:Peptidyl Transferases / Q000235:genetics*; D016133:Polymerase Chain Reaction; D014169:Transformation, Bacterial; D018440:beta-Lactam Resistance
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D009097:Multienzyme Complexes; D046915:Penicillin-Binding Proteins; D000658:Amoxicillin; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase