title: Distribution of different efflux pump genes in clinical isolates of multidrug-resistant Acinetobacter baumannii and their correlation with antimicrobial resistance.
abstract: OBJECTIVE
  Efflux pumps are one of the major mechanisms of antimicrobial resistance in Acinetobacter baumannii. This study aimed to understand the distribution of different types of pump genes in clinical isolates of multidrug-resistant A. baumannii (MDRAB) and to reveal the relationship between their presence and expression with antimicrobial resistance.
  
  
  METHODS
  MDRAB isolates were collected from five hospitals in Taiwan. Different categories of pump genes, including adeB, adeJ, macB, abeM, abeS, emrA-like, emrB-like, and craA, were chosen, and their presence in the collected isolates was determined. Three induced resistant strains of A. baumannii ATCC 17978 to tigecycline, imipenem, and amikacin were also included. The expressions of the selected pump genes were determined using quantitative reverse transcription-polymerase chain reaction.
  
  
  RESULTS
  Twenty-one MDRAB clinical isolates were obtained from five hospitals. All of the studied pump genes were present in the collected MDRAB isolates except one isolate that lacked the emrA-like gene. The gene expression of these efflux pumps was variable among the strains. The upregulation of the adeB, adeJ, and macB genes was responsible for tigecycline resistance, and the increased abeS expression was strongly related to amikacin resistance. Of all the antibiotics studied, tigecycline was the strongest inducer of gene expression for many efflux pumps in A. baumannii.
  
  
  CONCLUSIONS
  Efflux pump genes are universally present in the collected clinical MDRAB isolates. The upregulation of the adeB, adeJ, macB and abeS genes is more related with antibiotic resistance.
authors.affiliation: Department of Medicine, National Taiwan University Hospital Chu-Tung Branch, Hsin-Chu County, Taiwan; Institute of Molecular and Cellular Biology, National Tsing Hua University, Hsin-Chu City, Taiwan.
authors.forename: Ming-Feng
authors.initials: MF
authors.lastname: Lin
authors.affiliation: Institute of Molecular and Cellular Biology, National Tsing Hua University, Hsin-Chu City, Taiwan.
authors.forename: Yun-You
authors.initials: YY
authors.lastname: Lin
authors.affiliation: Department of Laboratory Medicine, Keelung Hospital, Minister of Health and Welfare, Keelung, Taiwan.
authors.forename: Chi-Chao
authors.initials: CC
authors.lastname: Tu
authors.affiliation: Institute of Molecular and Cellular Biology, National Tsing Hua University, Hsin-Chu City, Taiwan; Department of Life Science, National Tsing Hua University, Hsin-Chu City, Taiwan. Electronic address: cylan@life.nthu.edu.tw.
authors.forename: Chung-Yu
authors.initials: CY
authors.lastname: Lan
mesh_terms: D000151:Acinetobacter Infections / Q000382:microbiology*; D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000235:genetics* / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000493:pharmacokinetics / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D004269:DNA, Bacterial / Q000032:analysis; D024901:Drug Resistance, Multiple, Bacterial; D005798:Genes, Bacterial; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D012329:RNA, Bacterial / Q000032:analysis
chemical_list: C492436:AdeA protein, Acinetobacter baumannii; C445684:AdeB protein, Acinetobacter baumannii; C492437:AdeC protein, Acinetobacter baumannii; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D012329:RNA, Bacterial; C077168:emrA protein, Bacteria
keywords: Acinetobacter baumannii; antibiotic resistance; efflux pumps