title: Changes in gene cassettes of class 1 integrons among Escherichia coli isolates from urine specimens collected in Korea during the last two decades.
abstract: 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.
authors.affiliation: Department of Microbiology, School of Medicine, Kyungpook National University, Daegu, 700-422, Korea.
authors.forename: Hak Sun
authors.initials: HS
authors.lastname: Yu
authors.forename: Je Chul
authors.initials: JC
authors.lastname: Lee
authors.forename: Hee Young
authors.initials: HY
authors.lastname: Kang
authors.forename: Dong Woo
authors.initials: DW
authors.lastname: Ro
authors.forename: Jae Young
authors.initials: JY
authors.lastname: Chung
authors.forename: Young Sook
authors.initials: YS
authors.lastname: Jeong
authors.forename: Seong Ho
authors.initials: SH
authors.lastname: Tae
authors.forename: Chul Hee
authors.initials: CH
authors.lastname: Choi
authors.forename: Eun Young
authors.initials: EY
authors.lastname: Lee
authors.forename: Sung Yong
authors.initials: SY
authors.lastname: Seol
authors.forename: Yoo Chul
authors.initials: YC
authors.lastname: Lee
authors.forename: Dong Taek
authors.initials: DT
authors.lastname: Cho
mesh_terms: 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*
chemical_list: D004269:DNA, Bacterial; D016023:Integrins; D019426:Integrases