Characterization of antimicrobial resistance and class 1 integrons found in Escherichia coli isolates from humans and animals in Korea.
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.
Kang
Hee Young
HY
Department of Microbiology, Kyungpook National University School of Medicine, 101 Dongin-dong, Jung-gu, Daegu 700-422, Korea.
Jeong
Young Sook
YS
Oh
Jae Young
JY
Tae
Sung Ho
SH
Choi
Chul Hee
CH
Moon
Dong Chan
DC
Lee
Won Kil
WK
Lee
Yoo Chul
YC
Seol
Sung Yong
SY
Cho
Dong Taek
DT
Lee
Je Chul
JC
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*
D000900:Anti-Bacterial Agents