title: A novel multidrug resistance plasmid isolated from an Escherichia coli strain resistant to aminoglycosides.
abstract: OBJECTIVE
  Previous studies have reported several different plasmids that confer multidrug resistance (MDR) including resistance to aminoglycosides. In this study, we investigated the aminoglycoside resistance patterns for 224 Escherichia coli isolates from diseased chickens and ducks in China, characterized a novel MDR plasmid, and collected prevalence data on similar resistance plasmids.
  
  
  METHODS
  Antibiotic susceptibilities were determined using disc diffusion and the microdilution method. The plasmid pXZ was analysed by restriction fragment length polymorphism (RFLP) with EcoRI and SalI, and sequenced. The prevalence of similar resistance plasmids was assessed by multiplex PCR and by RFLP analysis.
  
  
  RESULTS
  Among the 224 E. coli isolates, 189 (84.4%) were resistant to streptomycin, 125 (55.8%) were resistant to kanamycin, 116 (51.8%) were resistant to gentamicin, 106 (47.3%) were resistant to neomycin and 98 (43.8%) were resistant to amikacin. Among the 224 E. coli isolates, 17 contained a plasmid with the MDR-encoding region of pXZ, which showed high-level resistance to aminoglycosides (MICs of gentamicin and amikacin ≥ 512 mg/L). The plasmid pXZ was digested into five fragments by EcoRI and six fragments by SalI. The plasmid pXZ was a circular DNA molecule of 76635 bp with a 51.65% guanine + cytosine content and included four resistance genes (rmtB, fosA3, bla(TEM-1) and bla(CTX-M-24)).
  
  
  CONCLUSIONS
  A novel MDR plasmid, pXZ, harbouring four resistance genes (rmtB, fosA3, bla(TEM-1) and bla(CTX-M)) was identified. To our knowledge, this is the first report of an aminoglycoside resistance plasmid harbouring the fosA3 gene.
authors.affiliation: Department of Preventive Veterinary Medicine,  College of Veterinary Medicine, Shandong Agricultural University, Shandong Taian, 271018,  China.
authors.forename: Hui
authors.initials: H
authors.lastname: Sun
authors.forename: Shasha
authors.initials: S
authors.lastname: Li
authors.forename: Zhijing
authors.initials: Z
authors.lastname: Xie
authors.forename: Fangfang
authors.initials: F
authors.lastname: Yang
authors.forename: Yani
authors.initials: Y
authors.lastname: Sun
authors.forename: Yanli
authors.initials: Y
authors.lastname: Zhu
authors.forename: Xiaomin
authors.initials: X
authors.lastname: Zhao
authors.forename: Shijin
authors.initials: S
authors.lastname: Jiang
mesh_terms: D000617:Aminoglycosides / Q000494:pharmacology*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002645:Chickens; D002681:China; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial; D004372:Ducks; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D058889:Molecular Typing; D010957:Plasmids / Q000302:isolation & purification*; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D011201:Poultry Diseases / Q000382:microbiology; D017422:Sequence Analysis, DNA
chemical_list: D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial