title: Conversion of OXA-66 into OXA-82 in clinical Acinetobacter baumannii isolates and association with altered carbapenem susceptibility.
abstract: OBJECTIVE
  Three clinical Acinetobacter baumannii isolates (A-C) were isolated from three separate patients during an outbreak in a hospital in Krakow, Poland. Isolate A was recovered first and was susceptible to carbapenems, whereas isolates B and C were resistant. The aim of this study was to investigate the differences in carbapenem susceptibility in these outbreak-related isolates.
  
  
  METHODS
  Clonal relatedness was determined using rep-PCR-based DiversiLab. The bla(OXA-51-like) genes and their upstream regions were sequenced. Expression of the genes encoding OXA-51-like and the three major porins CarO, OprD-like and 33-36 kDa Omp were investigated by semi-quantitative RT-PCR. Comparison of outer membrane protein (OMP) profiles was performed using SDS-PAGE. ISAba1-bla(OXA-82) was cloned into the shuttle vector pWH1266 and transferred into A. baumannii ATCC 17978.
  
  
  RESULTS
  The isolates were identical by rep-PCR and clustered with international clonal lineage 2. Sequencing of bla(OXA-51-like) revealed a conversion of OXA-66 (isolate A) into OXA-82 (isolates B and C). bla(OXA-82) was also associated with ISAba1. Expression analysis revealed overexpression of bla(OXA-82). There was no difference in OMP expression between the isolates. ISAba1-bla(OXA-82) conferred carbapenem resistance in ATCC 17978.
  
  
  CONCLUSIONS
  Carbapenem resistance in outbreak-related isolates was mediated by conversion of OXA-66 into OXA-82 and its subsequent overexpression. This further highlights the genome plasticity of A. baumannii, leading to carbapenem resistance.
authors.affiliation: Institute for Medical Microbiology, Immunology and Hygiene,  University of Cologne, Cologne,  Germany.
authors.forename: Esther
authors.initials: E
authors.lastname: Zander
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Chmielarczyk
authors.forename: Piotr
authors.initials: P
authors.lastname: Heczko
authors.forename: Harald
authors.initials: H
authors.lastname: Seifert
authors.forename: Paul G
authors.initials: PG
authors.lastname: Higgins
mesh_terms: D000151:Acinetobacter Infections / Q000453:epidemiology / Q000382:microbiology; D040981:Acinetobacter baumannii / Q000145:classification / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001425:Bacterial Outer Membrane Proteins / Q000032:analysis; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D015780:Carbapenems / Q000494:pharmacology*; D003001:Cloning, Molecular; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004196:Disease Outbreaks; D004591:Electrophoresis, Polyacrylamide Gel; D020869:Gene Expression Profiling; D005822:Genetic Vectors; D005838:Genotype; D006801:Humans; D008826:Microbial Sensitivity Tests; D058889:Molecular Typing; D011044:Poland / Q000453:epidemiology; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D014169:Transformation, Bacterial; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D015780:Carbapenems; D004269:DNA, Bacterial; D001618:beta-Lactamases; C063912:carbapenemase