多重耐药大肠埃希菌中I类整合子的研究

Study on Class 1 integrons in multidrug-resistant isolates of Escherichia coli

目的分析多重耐药大肠埃希菌中Ⅰ类整合子的流行情况和分子特性。方法对81株多重耐药大肠埃希菌用PCR法扩增细菌总DNA上的Ⅰ类整合子，对大小相同的Ⅰ类整合子进行酶切分析，对纯化后的Ⅰ类整合子作DNA测序，将DNA序列在GenBank中搜索，确定Ⅰ类整合子可变区基因盒的种类和排列。结果在48株（59．3％）细菌的总DNA上检测到Ⅰ类整合子，Ⅰ类整合子的大小约为600～3000bp，48株细菌各含1～2个Ⅰ类整合子，大小相同的Ⅰ类整合子有相同的酶切图谱，整合子中最常见的基因盒为dfr17（甲氧苄啶耐药基因）、aadA5（链霉素、大观霉素耐药基因），最主要的基因盒排列为dfr17-aadA5。结论整合子在多重耐药大肠埃希菌中广泛流行，整合子是介导细菌多重耐药性的重要分子机制。

Objective To analyze the prevalence and molecular characterization of Class 1 integrons in multidrug resistant Escherichia coli isolates. Methods Class 1 integrons were detected by PCR from the total DNA in 81 multidrug-resistant E. coli isolates. The RFLP analysis was carried out for amplicons of Class 1 integrons with identical size. The purified amplicons of Class 1 integrons were sequenced. The type and order of gene cassettes in integrons were analyzed by searching GenBank. Results Class 1 integrons were identified from total DNA in 48 （59.3 %） isolates. The size of Class 1 integrons ranged from about 600 bp to 3 000 bp. Each of the 48 isolates had 1 or 2 Class 1 integrons. Class 1 integrons indistinguishable with respect to size had identical restriction patterns. The predominant gene cassettes included dfr17 （encoding resistance to trimethoprim） and aadA5 （encoding resistance to streptomycin and spectinomycin）. The main order of inserted gene cassettes was dfr17-aadA 5. Conclusions Class 1 integrons are widespread in isolates of muhidrug-resistant E. coli. Integrons are important molecular mechanism in the development of muhidrug resistance.