title: [Active efflux of antibiotics as multiple-antibiotic-resistance mechanism in clinical strains of escherichia coli].
abstract: OBJECTIVE
  To investigate multiple-antibiotic-resistance mechanism in clinical strains of Escherichia coli.
  
  
  METHODS
  Accumulation of ciprofloxacin in clinical isolates of Escherichia coli was measured by fluorometry, and acrAB gene was identified by PCR and Southern blot. The levels of acrAB gene expression were measured by RT-PCR. DNA fragments were sequenced by automated fluorescence sequencing.
  
  
  RESULTS
  The state concentration of ciprofloxacin in multiple-antibiotic-resistant (Mar) strains was significantly lower than that in susceptible stsains (0.73 mg/L +/- 0.04 mg/L vs 2.00 mg/L +/- 0.07 mg/L A(660), P < 0.001). The level of acrAB gene expression in Mar strains was significantly higher than that in other strains. No deletion or point mutation in acrAB gene were found in Mar and susceptible clinical Escherichia coli isolates.
  
  
  CONCLUSIONS
  High expression of acrAB gene leads to multiple-antibiotic-resistance in clinical strains of Escherichia coli, and Mar operon may contribute to the regulation of acrAB gene expression.
authors.affiliation: Institute of Clinical Pharmacology, First Affiliated Hospital of Beijing Medical University, Beijing 100083, China.
authors.forename: X
authors.initials: X
authors.lastname: Zhang
authors.forename: J
authors.initials: J
authors.lastname: Li
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D002352:Carrier Proteins; D002939:Ciprofloxacin / Q000378:metabolism / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D024881:Drug Resistance, Bacterial; D018432:Drug Resistance, Multiple; D004926:Escherichia coli / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D029968:Escherichia coli Proteins; D005470:Fluorometry; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D008074:Lipoproteins / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics; D026901:Membrane Transport Proteins; D008826:Microbial Sensitivity Tests; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D002352:Carrier Proteins; D002939:Ciprofloxacin; D029968:Escherichia coli Proteins; D008074:Lipoproteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; C083497:AcrA protein, E coli; C083496:AcrB protein, E coli