title: Inhibition of the Mycobacterium tuberculosis reserpine-sensitive efflux pump augments intracellular concentrations of ciprofloxacin and enhances susceptibility of some clinical isolates.
abstract: OBJECTIVE
  Active efflux is known to play a major role in the resistance of many bacteria to antibiotics. To evaluate the possibility of overcoming resistance by suppressing the efflux, we determined the effect of reserpine, an efflux pump inhibitor.
  
  
  METHODS
  Intracellular accumulations and the minimal inhibitory concentrations (MICs) of ciprofloxacin in M. tuberculosis H37Rv and 16 clinical isolates were determined, compared, and analyzed. Nine of the clinical isolates were resistant to isoniazid and rifampin (multiple-drug resistant MDR). Five of these were resistant to ciprofloxacin.
  
  
  RESULTS
  A reserpine-inhibited efflux system was identified in the H37Rv control and 10:1 (90.9%) of ciprofloxacin-susceptible and 4:1 (80%) of ciprofloxacin-resistant clinical isolates. The MIC of ciprofloxacin decreased in the presence of reserpine in 3/10 (30%) of the ciprofloxacin-susceptible and 2/4 (50%) of the MDR ciprofloxacin-resistant strains that expressed efflux pumps. Two of the efflux-positive, ciprofloxacin-resistant strains in which the MIC of ciprofloxacin was not decreased by reserpine were found to carry a D94A gyrA mutation. In contrast, two strains with the D94G gyrA mutation were susceptible to ciprofloxacin in the presence of reserpine. An efflux-negative strain, highly resistant to multiple antibiotics, was found to have a novel G247S mutation that differs from known mutations in the QRDR region of the gyrA gene.
  
  
  CONCLUSIONS
  These findings indicate t hat reserpine can increase intracellular concentrations of ciprofloxacin, but is unable to overcome other mechanisms of resistance in clinical isolates.
authors: Section of Microbiology, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan; Department of Medical Technology, Fooyin University, Ta-Liao Hsiang, Kaohsiung Hsien, Taiwan; Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan.
authors: Tsi-Shu
authors: TS
authors: Huang
authors: Department of Internal Medicine, Ohio State University, Columbus, Ohio, USA.
authors: Calvin M
authors: CM
authors: Kunin
authors: Department of Fragrance and Cosmetic Science, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors: Hui-Min
authors: HM
authors: Wang
authors: Institute of Biochemistry and Molecular Biology, National Taiwan University, Taipei, Taiwan.
authors: Bo-Shiun
authors: BS
authors: Yan
authors: Department of Medical Technology, Fooyin University, Ta-Liao Hsiang, Kaohsiung Hsien, Taiwan.
authors: Shiao-Ping
authors: SP
authors: Huang
authors: Section of Microbiology, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan; Infectious Diseases, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan; Graduate Institute of Environmental Education, National Kaohsiung Normal University, Kaohsiung, Taiwan.
authors: Yao-Shen
authors: YS
authors: Chen
authors: Infectious Diseases, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan.
authors: Susan Shin-Jung
authors: SS
authors: Lee
authors: Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan. Electronic address: wjsyu@ym.edu.tw.
authors: Wan-Jr
authors: WJ
authors: Syu
mesh_terms: D018759:Adrenergic Uptake Inhibitors / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000493:pharmacokinetics; D002463:Cell Membrane Permeability / Q000187:drug effects*; D002939:Ciprofloxacin / Q000493:pharmacokinetics; D027081:DNA Gyrase / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000187:drug effects* / Q000235:genetics; D008826:Microbial Sensitivity Tests; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000235:genetics; D012110:Reserpine / Q000494:pharmacology
chemical_list: D018759:Adrenergic Uptake Inhibitors; D000900:Anti-Bacterial Agents; D002939:Ciprofloxacin; D012110:Reserpine; D027081:DNA Gyrase
keywords: Mycobacterium tuberculosis; efflux; fluoroquinolones