title: OXA-162, a novel variant of OXA-48 displays extended hydrolytic activity towards imipenem, meropenem and doripenem.
abstract: BACKGROUND
  Isolation and characterization of OXA-162, a novel variant of OXA-48.
  
  
  OBJECTIVE
  Klebsiella pneumoniae isolate with decreased susceptibility to carbapenems was recovered from a Turkish patient. This study aimed at characterizing the carbapenem resistance determinants of this isolate.
  
  
  METHODS
  Antibiotic susceptibility tests, analytic isoelectric focusing (IEF), cloning and sequencing were performed. Cloned β-lactamase was purified by means of preparative gel electrophoresis and the kinetic constants were determined under initial rate conditions.
  
  
  RESULTS
  The identified bla(OXA-162) gene was located on a ca. 45-kb plasmid carrying a transposon consisted of two IS1999-2 elements. OXA-162 differed from OXA-48 by a single amino acid substitution (Thr213Ala) which increased the catalytic efficiency (k(cat)/K(M)) of OXA-162 towards imipenem and meropenem. Also this substitution caused a gain of hydrolysis ability towards doripenem. Analysis of OXA-162 model implied that the amino acid change might generate an extension in the opening of the substrate entry site and might cause extended hydrolytic activity towards imipenem, meropenem and doripenem.
  
  
  CONCLUSIONS
  OXA-162, a derivative of OXA-48 has enhanced catalytic properties.
authors: Medical Biology Department, Kocaeli University Medical School , Kocaeli , Turkey.
authors: Murat
authors: M
authors: Kasap
authors: Sinem
authors: S
authors: Torol
authors: Fetiye
authors: F
authors: Kolayli
authors: Devrim
authors: D
authors: Dundar
authors: Haluk
authors: H
authors: Vahaboglu
mesh_terms: D055162:Biocatalysis; D015780:Carbapenems / Q000737:chemistry / Q000378:metabolism*; D003001:Cloning, Molecular; D004251:DNA Transposable Elements / Q000235:genetics; D000077726:Doripenem; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D006801:Humans; D006868:Hydrolysis; D015378:Imipenem / Q000737:chemistry / Q000378:metabolism*; D007711:Klebsiella pneumoniae / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D000077731:Meropenem; D008958:Models, Molecular; D010957:Plasmids / Q000235:genetics; D013845:Thienamycins / Q000737:chemistry / Q000378:metabolism*; D001618:beta-Lactamases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D015780:Carbapenems; D004251:DNA Transposable Elements; D013845:Thienamycins; D015378:Imipenem; D000077726:Doripenem; D001618:beta-Lactamases; C108449:oxacillinase; D000077731:Meropenem