title: Characterization of antimicrobial resistance and class 1 integrons found in Escherichia coli isolates from humans and animals in Korea.
abstract: OBJECTIVE
  Antimicrobial resistance and class 1 integrons found in Escherichia coli isolates from humans and animals in Korea were characterized.
  
  
  METHODS
  E. coli isolates were examined for susceptibility to antimicrobial agents. Integrase genes were amplified. Gene cassette regions for classes 1 and 2 integrons were amplified and sequenced. Conjugal transfer and Southern hybridization were performed to determine the genetic localization of class 1 integrons. The clonal relationship of E. coli isolates carrying an identical cassette array was analysed by PFGE.
  
  
  RESULTS
  Commensal E. coli isolates from animals were highly resistant to commonly used antimicrobial agents such as tetracycline, sulfamethoxazole, streptomycin, ampicillin and carbenicillin. Integrons were most prevalent in commensal E. coli isolates from poultry (44%), followed by clinical isolates from humans (33%), commensal isolates from swine (23%) and humans (13%). dfrA17-aadA5, dfrA12-orfF-aadA2 and aadA1 were found most frequently in E. coli isolates from humans, poultry and swine, respectively. Class 1 integrons were mostly located in conjugative plasmids. E. coli isolates carrying an identical cassette array were phylogenetically unrelated.
  
  
  CONCLUSIONS
  The use of antibiotics is strongly associated with antimicrobial resistance. E. coli isolates from different sources may select a specific gene cassette by antibiotic selective pressure, which results in differences in class 1 integrons. The horizontal transfer of class 1 integrons through conjugative plasmids seems to be responsible for wide dissemination of a particular type of class 1 integron.
authors.affiliation: Department of Microbiology, Kyungpook National University School of Medicine, 101 Dongin-dong, Jung-gu, Daegu 700-422, Korea.
authors.forename: Hee Young
authors.initials: HY
authors.lastname: Kang
authors.forename: Young Sook
authors.initials: YS
authors.lastname: Jeong
authors.forename: Jae Young
authors.initials: JY
authors.lastname: Oh
authors.forename: Sung Ho
authors.initials: SH
authors.lastname: Tae
authors.forename: Chul Hee
authors.initials: CH
authors.lastname: Choi
authors.forename: Dong Chan
authors.initials: DC
authors.lastname: Moon
authors.forename: Won Kil
authors.initials: WK
authors.lastname: Lee
authors.forename: Yoo Chul
authors.initials: YC
authors.lastname: Lee
authors.forename: Sung Yong
authors.initials: SY
authors.lastname: Seol
authors.forename: Dong Taek
authors.initials: DT
authors.lastname: Cho
authors.forename: Je Chul
authors.initials: JC
authors.lastname: Lee
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015139:Blotting, Southern; D003227:Conjugation, Genetic; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000382:microbiology*; D006801:Humans; D032023:Integrons / Q000235:genetics*; D007420:Intestine, Large / Q000382:microbiology; D007723:Korea / Q000453:epidemiology; D008826:Microbial Sensitivity Tests; D010957:Plasmids / Q000235:genetics; D011200:Poultry / Q000382:microbiology*; D013552:Swine / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents