title: Amino acid substitutions of quinolone resistance determining regions in GyrA and ParC associated with quinolone resistance in Acinetobacter baumannii and Acinetobacter genomic species 13TU.
abstract: OBJECTIVE
  Amino acid substitutions in GyrA and ParC are associated with resistance to quinolones in Acinetobacter baumannii (A baumannii), but this association is rarely elucidated in Acinetobacter genomic species (AGS) 13TU. This study aims to compare the association of amino acid substitutions in GyrA and ParC with quinolone resistance in A baumannii and AGS 13TU in Taiwan.
  
  
  METHODS
  Eleven representative strains of A baumannii and 13 strains of AGS 13TU were selected from 402 bacteremic isolates. The sequences of quinolone resistance determining regions of gyrA and parC were determined. Minimal inhibitory concentrations (MICs) of nalidixic acid, ciprofloxacin, levofloxacin and moxifloxacin were determined by agar dilution method.
  
  
  RESULTS
  Ser83Leu substitution in GyrA in A baumannii (one strain) was associated with resistance to all tested quinolones. This substitution plus a Ser80Leu or Ser80Tyr in ParC in A baumannii (four strains) and AGS 13TU (two strains) were associated with higher MICs of all quinolones. All but one quinolone MICs of A baumannii (one strain) and AGS 13TU (two strains) carrying a single substitution Ser56Asn in ParC remained in the susceptibility breakpoint. The Ser83Leu substitution in GyrA, even with additional Ser56Asn substitution in ParC, was associated with resistance to only nalidixic acid, but not other newer quinolones in AGS 13TU (two strains).
  
  
  CONCLUSIONS
  A baumannii and AGS 13TU possessed similar quinolone resistance associated with amino acid substitutions in GyrA and ParC. Further study with more strains is needed to determine whether a single Ser83Leu substitution in GyrA was associated with a high level of quinolone MIC only in A baumannii, but not in AGS 13TU.
authors.affiliation: Division of Infectious Diseases, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan.
authors.forename: Yen-Hung
authors.initials: YH
authors.lastname: Liu
authors.forename: Shu-Chen
authors.initials: SC
authors.lastname: Kuo
authors.forename: Yi-Tzu
authors.initials: YT
authors.lastname: Lee
authors.forename: Ian C Y
authors.initials: IC
authors.lastname: Chang
authors.forename: Su-Pen
authors.initials: SP
authors.lastname: Yang
authors.forename: Te-Li
authors.initials: TL
authors.lastname: Chen
authors.forename: Chang-Phone
authors.initials: CP
authors.lastname: Fung
mesh_terms: D000150:Acinetobacter / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D000151:Acinetobacter Infections / Q000382:microbiology*; D019943:Amino Acid Substitution; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D016470:Bacteremia / Q000382:microbiology; D027081:DNA Gyrase / Q000235:genetics*; D027101:DNA Topoisomerase IV / Q000235:genetics*; D024881:Drug Resistance, Bacterial; D006801:Humans; D008826:Microbial Sensitivity Tests; D020125:Mutation, Missense; D015363:Quinolones / Q000494:pharmacology*; D017422:Sequence Analysis, DNA; D013624:Taiwan
chemical_list: D000900:Anti-Bacterial Agents; D015363:Quinolones; D027101:DNA Topoisomerase IV; D027081:DNA Gyrase