title: Influence of induced ciprofloxacin resistance on efflux pump activity of Klebsiella pneumoniae.
abstract: OBJECTIVE
  The efflux pump (EP) is one of the major mechanisms of antibiotic resistance in Klebsiella pneumoniae. However, there are few reports on the effect of the abuse of antibiotic use on the activity of EPs. To determine whether the use of low efficacy antibiotics has any effect on the activity of EPs and induces drug resistance in K. pneumoniae, we investigated the effect of ciprofloxacin on the activity of EPs in K. pneumoniae strains.
  
  
  METHODS
  Sixteen susceptible K. pneumoniae strains were isolated from patients and their minimum inhibitory concentrations (MICs) of ciprofloxacin were measured in the absence and presence of the pump inhibitor carbonyl cyanide m-chlorophenyl hydrazone (CCCP). The strains were then induced with a gradient of ciprofloxacin until the MICs of the strains showed no further increase, to obtain induced resistant strains. The EP activities of the strains before and after induction were compared using EP inhibition and ethidium bromide (EtBr) accumulation assays.
  
  
  RESULTS
  The MIC values of the strains were 16‒256 times higher after induction than before induction. In the presence of CCCP, the MIC values of 50% of the induced strains were 2‒4-fold lower than that in the absence of this inhibitor. The EtBr accumulation assay showed that the fluorescence of EtBr in the induced cells was lower than that in the cells before induction.
  
  
  CONCLUSIONS
  EPs are widespread in susceptible and drug-resistant K. pneumoniae strains. Induction with ciprofloxacin may increase the activity of EPs in K. pneumoniae. The EtBr accumulation assay is more sensitive than the EP inhibition assay in evaluating the activity of EPs in K. pneumoniae.
authors.affiliation: Department of Internal Medicine, School of Medicine, Ningbo University, Ningbo 315211, China; Stem Cell Laboratory, Ningbo No. 2 Hospital, Ningbo 315010, China; Clinical Laboratory, Ningbo No. 2 Hospital, Ningbo 315010, China; Emergency Department, Ningbo No. 2 Hospital, Ningbo 315010, China.
authors.forename: Hai-qin
authors.initials: HQ
authors.lastname: Zhong
authors.forename: Shun
authors.initials: S
authors.lastname: Zhang
authors.forename: Hong
authors.initials: H
authors.lastname: Pan
authors.forename: Ting
authors.initials: T
authors.lastname: Cai
mesh_terms: D000900:Anti-Bacterial Agents / Q000493:pharmacokinetics / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000378:metabolism; D001693:Biological Transport, Active / Q000187:drug effects; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002939:Ciprofloxacin / Q000493:pharmacokinetics / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D004996:Ethidium / Q000493:pharmacokinetics; D006801:Humans; D007711:Klebsiella pneumoniae / Q000187:drug effects* / Q000378:metabolism* / Q000472:pathogenicity; D026901:Membrane Transport Proteins / Q000378:metabolism; D008826:Microbial Sensitivity Tests
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D002939:Ciprofloxacin; D004996:Ethidium