Changes in gene cassettes of class 1 integrons among Escherichia coli isolates from urine specimens collected in Korea during the last two decades.
Gene cassettes of class 1 integrons in Escherichia coli isolates from urine specimens collected in Korea during the last 2 decades were characterized. intI1 was detected in 54% of the isolates, yet gene cassette regions were amplified in only 43% of the isolates. intI2 was detected in 29 (5%) isolates, and no intI3 was detected in this study. Twenty-one different genes, including genes encoding resistance to antibiotics, an alcohol dehydrogenase gene (adhE), and unknown genes, were detected. The genes most commonly found in class 1 integrons were those for aminoglycoside and trimethoprim resistance. The occurrence of aminoglycoside resistance genes in class 1 integrons decreased, and the presence of dfr genes increased rapidly, during the last 2 decades. Single-gene cassettes were predominant during the 1980s, while multigene cassettes predominated from the 1990s on. The aadA1, aadA2, and blaP1-aadA2 gene cassettes were frequently found in isolates from the 1980s but were not detected in isolates recovered since 2000. dfrA12-aadA2 and dfrA17-aadA5 were the most prevalent gene cassettes among isolates recovered from the 1990s on. In conclusion, class 1 integrons would appear to be responsible for resistance to antibiotics commonly used to treat urinary tract infections, and selection of a specific gene cassette was found to occur over the course of time.
Yu
Hak Sun
HS
Department of Microbiology, School of Medicine, Kyungpook National University, Daegu, 700-422, Korea.
Lee
Je Chul
JC
Kang
Hee Young
HY
Ro
Dong Woo
DW
Chung
Jae Young
JY
Jeong
Young Sook
YS
Tae
Seong Ho
SH
Choi
Chul Hee
CH
Lee
Eun Young
EY
Seol
Sung Yong
SY
Lee
Yoo Chul
YC
Cho
Dong Taek
DT
D015139:Blotting, Southern; D002874:Chromosome Mapping; D004269:DNA, Bacterial / Q000235:genetics / Q000302:isolation & purification; D004926:Escherichia coli / Q000235:genetics* / Q000302:isolation & purification*; D006801:Humans; D019426:Integrases / Q000235:genetics; D016023:Integrins / Q000235:genetics; D032023:Integrons / Q000235:genetics*; D007723:Korea; D016133:Polymerase Chain Reaction / Q000379:methods; D014556:Urine / Q000382:microbiology*
D004269:DNA, Bacterial; D016023:Integrins; D019426:Integrases