title: [Molecular mechanisms of quinolone resistance in Aeromonas hydrophilia].
abstract: OBJECTIVE
  To study the resistance mechanisms to quinolones in Aeromonas hydrohila isolated from aquatic animals.
  
  
  METHODS
  The drug-resistant spectrum of 23 strains was determined. Quinolone-resistance determining regions of gyrA and parC genes in both screened and in-vitro induction drug-resistant strains were analyzed. Then the detection of quinolone drugs relative efflux pump genes qepA, oqxA and mdfA was performed. The qnrA, qnrB, qnrC, qnrD and qnrS genes were also analyzed at the same time.
  
  
  RESULTS
  All organisms were resistant to more than 5 drugs; 39.1% (9/23) of the isolates were quinolone resistant, of which 55.6% (5/9) were enrofloxacin resistant. All the enrofloxacin-resistant isolates harbored qnrS gene, but none of the enrofloxacin-resistant strains harbored qnrA, qnrB, qnrC , qnrD genes and the efflux pump genes of qepA, oqxA and mdfA. AH19 possessed the gyrA and parC genes double mutation, plasmid-mediated quinolone resistance gene qnrS and efflux pump, 3 drug resistance mechanisms simultaneously, while the two drug-resistant mechanisms of AH4, AH7 and AH20 were gyrA and parC genes double mutation and qnrS gene. GyrA gene mutation and qnrS gene occurred in AH6. Compared to the strain ATCC7966, the in-vitro induction drug-resistant strain ATCC7966-QR had both the gyrA and parC genes mutation.
  
  
  CONCLUSIONS
  The mechanisms of resistance to quinolones in the A. hydrophila isolates of this study mainly depended on the existence of plasmid-mediated gene qnrS and the variation of the target site of quinolone drugs, whereas, the drug resistance mechanism relying on the efflux pump system only existed in individual strains.
authors.forename: Yifeng
authors.initials: Y
authors.lastname: Fang
authors.forename: Xiaoyi
authors.initials: X
authors.lastname: Pan
authors.forename: Lingyun
authors.initials: L
authors.lastname: Lin
authors.forename: Jinyu
authors.initials: J
authors.lastname: Shen
authors.forename: Wenlin
authors.initials: W
authors.lastname: Yin
authors.forename: Jiayun
authors.initials: J
authors.lastname: Yao
authors.forename: Guijie
authors.initials: G
authors.lastname: Hao
authors.forename: Yang
authors.initials: Y
authors.lastname: Xu
mesh_terms: D000333:Aeromonas / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D024881:Drug Resistance, Bacterial; D005393:Fish Diseases / Q000382:microbiology*; D005399:Fishes; D016905:Gram-Negative Bacterial Infections / Q000382:microbiology / Q000662:veterinary*; D008826:Microbial Sensitivity Tests; D009154:Mutation; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D015363:Quinolones / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D015363:Quinolones