title: Heterogeneous hydrolytic features for OXA-48-like β-lactamases.
abstract: OBJECTIVE
  Carbapenem-hydrolysing class D β-lactamases of the OXA-48 type are increasingly reported from Enterobacteriaceae. β-Lactamase OXA-48 hydrolyses penicillins very efficiently, but carbapenems only weakly and spares broad-spectrum cephalosporins. Recently, diverse OXA-48-like β-lactamases have been identified worldwide (OXA-162, OXA-181, OXA-163, OXA-204 and OXA-232). They differ by few amino acid substitutions or by amino acid deletions.
  
  
  METHODS
  blaOXA-48, blaOXA-162, blaOXA-163, blaOXA-181, blaOXA-204 and blaOXA-232 were cloned into the same expression vector and expressed in the same Escherichia coli background. Kinetic studies were performed with enzymes purified by ion-exchange chromatography. Determination of hydrolytic activities was performed by UV spectrophotometry. MICs were determined for all recombinant strains, using as background either the WT E. coli TOP10 strain or a porin-deficient E. coli strain.
  
  
  RESULTS
  Kinetic studies showed that OXA-162 and OXA-204 shared the same hydrolytic properties as OXA-48. On the other hand, OXA-181 possessed a higher ability to hydrolyse carbapenems, while OXA-232 hydrolysed those substrates less efficiently. In contrast to the other OXA-48-like β-lactamases, OXA-163 hydrolysed broad-spectrum cephalosporins very efficiently, but did not possess significant carbapenemase activity. Although several of these OXA-48-like enzymes possess low activity against carbapenems, MICs of carbapenems were significantly elevated when determined for strains possessing permeability defects.
  
  
  CONCLUSIONS
  A detailed comparative analysis of the kinetic properties of the OXA-48-like β-lactamases is provided here. It clarifies the respective features of each OXA-48-like variant and their respective impacts in terms of carbapenem resistance.
authors.affiliation: INSERM U914 'Emerging Resistance to Antibiotics', K.-Bicêtre, France LabEx LERMIT, Faculté de Médecine Paris Sud, K.-Bicêtre, France.
authors.forename: Saoussen
authors.initials: S
authors.lastname: Oueslati
authors.affiliation: INSERM U914 'Emerging Resistance to Antibiotics', K.-Bicêtre, France LabEx LERMIT, Faculté de Médecine Paris Sud, K.-Bicêtre, France Centre National Associé-Centre de Référence des Résistances aux Antibiotiques, K.-Bicêtre, France Medical and Molecular Microbiology, Department of Medicine, Faculty of Science, University of Fribourg, Fribourg, Switzerland HFR-Hôpital Cantonal, Fribourg, Switzerland.
authors.forename: Patrice
authors.initials: P
authors.lastname: Nordmann
authors.affiliation: INSERM U914 'Emerging Resistance to Antibiotics', K.-Bicêtre, France LabEx LERMIT, Faculté de Médecine Paris Sud, K.-Bicêtre, France Centre National Associé-Centre de Référence des Résistances aux Antibiotiques, K.-Bicêtre, France Medical and Molecular Microbiology, Department of Medicine, Faculty of Science, University of Fribourg, Fribourg, Switzerland laurent.poirel@unifr.ch.
authors.forename: Laurent
authors.initials: L
authors.lastname: Poirel
mesh_terms: D002852:Chromatography, Ion Exchange; D003001:Cloning, Molecular; D004755:Enterobacteriaceae / Q000201:enzymology*; D015870:Gene Expression; D006868:Hydrolysis; D007700:Kinetics; D008826:Microbial Sensitivity Tests; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet; D001618:beta-Lactamases / Q000235:genetics / Q000378:metabolism*; D047090:beta-Lactams / Q000378:metabolism*
chemical_list: D011994:Recombinant Proteins; D047090:beta-Lactams; D001618:beta-Lactamases
keywords: carbapenemases; class D β-lactamases; enzymatic activity