Variable Gene Cassette Patterns of Class 1 Integron-Associated Drug-Resistant Escherichia Coli in Taiwan

針對住院病人分離之大腸桿菌進行第一型integron之研究，並進一步分析其所攜帶基因片匣之穩定性及變異。實驗中挑選436株分離自2002年之大腸桿菌，以PCR及核甘酸定序探討第一型integron之特性並利用接合反應及南方雜交法分析第一型integron存在菌株位置。結果有64%之臨床菌株攜帶第一型integron，分析顯示這些第一型integron攜帶13種不同抗藥基因片匣及兩種未知基因片匣，而主要之片匣為aadA及dfrA。在大腸桿菌發現之新基因片匣及片匣組合分別為aacA4、linF及orfD-aacA4-catB8、aadA1-linF。而dfrA12-orfF-aadA2是目前穩定存在的基因片匣，而第一型integron及dfrA17-aadA5片匣則發現位於菌株同一轉移性質體上，並且可藉質體轉移在菌株問傳遞。所以臨床抗藥菌株增加可能的解釋為抗生素篩選壓力及integron廣泛存在的結果。在抗生素篩選壓力下，攜帶抗藥基因之片匣可能不容易自菌株中遺失。因此認為integron攝入抗藥基因並藉質體於菌種問散佈抗藥性的角色將可能持續威脅臨床抗生素之使用及治療。

關鍵字

aadA1-linF ；接合性質體； dfrA17-aadA5 ；大腸桿菌； orfD-aacA4-catB8

並列摘要

This study characterized class 1 integrons in Escherichia coli in Taiwan. The stability and changes in gene cassettes inserted into integrons were also evaluated. The study included 436 clinical strains of E. coli isolated in 2002. Class 1 integrons were characterized by polymerase chain reaction and direct sequencing. Genetic localization of class 1 integrons was determined by conjugal transfer and Southern hybridization. The results indicated that 64% of E. coli isolates carried class 1 integrons. Molecular analysis revealed that the class 1 integrons harbored 13 different antimicrobial resistance gene cassettes and two unknown gene cassettes; the predominant cassettes were aadA and dfrA. Novel gene cassettes first recovered from E. coli were aacA4 and linF. Cassette arrays orfD-aacA4-catB8 and aadA1-linF were also observed. Gene cassette dfrA12-orfF-aadA2 was stable. The class 1 integron and dfrA17-aadA5 gene cassette were located on the same transferable plasmids and were capable of transmission. Therefore, the increased drug resistance of clinical isolates may be explained by antibiotic selective pressure and widespread presence of integrons. Under antibiotic selective pressure, gene cassette-mediated resistance may not be easily lost. The potential role of integrons in the uptake and dissemination of resistance genes by plasmid between species of bacteria may decrease the therapeutic effectiveness of antibiotics.

並列關鍵字

aadA1-linF ； conjugative plasmid ； dfrA17-aadA5 ； Escherichia coli ； orfD-aacA4-catB8

國際替代計量

Variable Gene Cassette Patterns of Class 1 Integron-Associated Drug-Resistant Escherichia Coli in Taiwan

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