title: Massive reduction in methicillin resistance by transposon inactivation of the normal PBP2 in a methicillin-resistant strain of Staphylococcus aureus.
abstract: Screening of a large transposon library constructed in the background of a highly and homogeneously methicillin-resistant Staphylococcus aureus (MRSA) strain (methicillin MIC 1,600 micrograms/ml) for Tn551 mutants with reduced resistance, identified mutant RUSA130 with a methicillin MIC of 12 micrograms/ml. Cloning in E. coli followed by sequencing located the Tn551 insert omega 703 near the C-terminal of the PBP2 gene. Penicillin-binding assays with mutant RUSA130 showed the presence of normal amounts of penicillin-binding protein 2A (PBP2A) but the absence of PBP2. These observations suggest that the mecA gene product PBP2A is not the sole catalyst of peptidoglycan synthesis in MRSA growing in the presence of beta-lactam antibiotics, since an intact PBP2 is also essential for the optimal expression of methicillin resistance in MRSA.
authors.affiliation: Molecular Genetics Unit, Universidade Nova de Lisboa (UNL), Oeiras, Portugal.
authors.forename: M G
authors.initials: MG
authors.lastname: Pinho
authors.forename: A M
authors.initials: AM
authors.lastname: Ludovice
authors.forename: S
authors.initials: S
authors.lastname: Wu
authors.forename: H
authors.initials: H
authors.lastname: De Lencastre
mesh_terms: D001426:Bacterial Proteins; D001435:Bacteriophages / Q000235:genetics; D002352:Carrier Proteins / Q000276:immunology*; D003470:Culture Media; D004251:DNA Transposable Elements / Q000187:drug effects* / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics / Q000276:immunology; D006602:Hexosyltransferases; D016106:Methicillin Resistance / Q000235:genetics*; D002267:Muramoylpentapeptide Carboxypeptidase / Q000276:immunology*; D009154:Mutation; D046915:Penicillin-Binding Proteins; D010458:Peptidyl Transferases; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics; D014161:Transduction, Genetic / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D003470:Culture Media; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D046915:Penicillin-Binding Proteins; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase