title: Genetic basis of multidrug-resistant Acinetobacter baumannii clinical isolates from three university hospitals in Chungcheong Province, Korea.
abstract: BACKGROUND
  The emergence of multidrug-resistant (MDR) Acinetobacter baumannii as an important opportunistic pathogen has given rise to significant therapeutic challenges in the treatment of nosocomial infections. In the present study, we assess the antibiotic resistance mechanisms of MDR A. baumannii strains by estimating the prevalence of antibiotic resistance determinants, including integrons, β-lactamases, str genes, and gyrA and parC mutations.
  
  
  METHODS
  Thirty-five MDR A. baumannii clinical isolates were collected from 3 Korean university hospitals over a 2-yr period. A. baumannii was confirmed by rpoB gene analysis. For each isolate, the minimal inhibitory concentrations (MICs) of 9 antibiotics were determined by the agar dilution method. PCR and DNA sequencing were used to identify the genes that potentially contribute to each resistance phenotype.
  
  
  RESULTS
  Of the 35 MDR A. baumannii isolates examined, 7 antibiotic resistance gene determinants were detected. These resistance gene determinants included the gene bla(OXA-23), with an upstream element ISAba1 to promote increased gene expression and subsequent resistance to carbapenems, in 8 isolates (22.9%); aacA4, located within class 1 integrons, in 7 isolates (20.0%); and fluoroquinolone resistance conferred by gyrA and parC sense mutations in 31 isolates.
  
  
  CONCLUSIONS
  Of the 35 MDR A. baumannii isolates, 26 (74.3%) from both outbreak and sporadic cases possessed at least 4 of the 7 antibiotic resistance gene determinants that give rise to the MDR phenotype. The co-occurrence of several resistance determinants may present a significant threat.
authors.affiliation: Department of Laboratory Medicine, College of Medicine, Chungnam National University, Daejeon, Korea.
authors.forename: Sun Hoe
authors.initials: SH
authors.lastname: Koo
authors.forename: Kye Chul
authors.initials: KC
authors.lastname: Kwon
authors.forename: Hye Hyun
authors.initials: HH
authors.lastname: Cho
authors.forename: Ji Youn
authors.initials: JY
authors.lastname: Sung
mesh_terms: D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics*; D015780:Carbapenems / Q000494:pharmacology; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D006785:Hospitals, University; D006801:Humans; D032023:Integrons / Q000235:genetics; D008826:Microbial Sensitivity Tests; D056910:Republic of Korea; D017422:Sequence Analysis, DNA
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D015780:Carbapenems