title: High rates of resistance to colistin and polymyxin B in subgroups of Acinetobacter baumannii isolates from Korea.
abstract: OBJECTIVE
  To investigate antimicrobial resistance in clinical isolates of Acinetobacter spp. from two Korean hospitals.
  
  
  METHODS
  Two hundred and sixty-five isolates of Acinetobacter spp. from two Korean hospitals were collected and were identified to species level using partial rpoB gene sequences. Antimicrobial susceptibility testing was performed using a broth microdilution method.
  
  
  RESULTS
  rpoB gene sequences indicated that 214 isolates (80.8%) were Acinetobacter baumannii, and allowed these to be classified into three subgroups (I, II and III); 142 isolates (53.6%) belonged to subgroup I, 54 (20.4%) to subgroup II and 18 (6.8%) to subgroup III. Forty-eight isolates (18.1%) and 74 isolates (27.9%) were resistant to polymyxin B and colistin, respectively. However, antimicrobial resistance rates varied markedly between subgroups. While A. baumannii subgroup I showed low resistance rates to polymyxin B and colistin (2.1% and 7.0%, respectively), subgroups II and III showed high resistance rates to these antibiotics (38.9% and 64.8% in subgroup II and 72.2% and 88.9%, in subgroup III, respectively). Multidrug resistance was also significantly more frequent in subgroup I (45.1%) than in subgroups II and III (13.0% and 16.7%, respectively).
  
  
  CONCLUSIONS
  Our data indicate that subgroup identification of A. baumannii may aid selection of appropriate antimicrobial agents for the treatment of Acinetobacter infections.
authors.affiliation: Department of Molecular Cell Biology, Sungkyunkwan University School of Medicine, Suwon, Korea.
authors.forename: Kwan Soo
authors.initials: KS
authors.lastname: Ko
authors.forename: Ji Yoeun
authors.initials: JY
authors.lastname: Suh
authors.forename: Ki Tae
authors.initials: KT
authors.lastname: Kwon
authors.forename: Sook-In
authors.initials: SI
authors.lastname: Jung
authors.forename: Kyong-Hwa
authors.initials: KH
authors.lastname: Park
authors.forename: Cheol In
authors.initials: CI
authors.lastname: Kang
authors.forename: Doo Ryeon
authors.initials: DR
authors.lastname: Chung
authors.forename: Kyong Ran
authors.initials: KR
authors.lastname: Peck
authors.forename: Jae-Hoon
authors.initials: JH
authors.lastname: Song
mesh_terms: D000151:Acinetobacter Infections / Q000453:epidemiology / Q000382:microbiology; D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000235:genetics; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D003091:Colistin / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial; D007723:Korea / Q000453:epidemiology; D010802:Phylogeny; D011112:Polymyxin B / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D011112:Polymyxin B; D003091:Colistin