尿液分离大肠埃希菌耐复方磺胺甲噁唑相关基因研究

目的了解尿液分离大肠埃希菌对复方磺胺甲噁唑耐药的相关基因的分布特征。方法从临床尿液标本中分离得到145株大肠埃希菌株,采用K-B法对甲氧苄啶和复方磺胺甲噁唑的药物敏感性测定。对甲氧苄啶耐药菌株中的Ⅰ、Ⅱ类整合子进行扩增,并酶切分析相应的可变区,从具有相同酶切图谱的菌株中各选取一株进行测序。测序结果在GenBank中进行核酸序列同源性搜索。对复方磺胺甲噁唑耐药株扩增sul1、sul2、sul3三种基因。对Ⅰ类整合子阳性菌株进行ERIC-PCR基因分型。结果对甲氧苄啶和复方磺胺甲噁唑耐药率分别为73.1%、79.9%。在109株耐甲氧苄啶菌株中,I类整合子含有7种基因盒类型,Ⅱ类仅含有1种类型基因盒,发现4种类型dfrA基因。在119株耐复方磺胺甲噁唑菌株中,sul1阳性72株,sul2阳性81株,sul3阳性2株。在甲氧苄啶和(或)复方磺胺甲噁唑耐药株中,80株Ⅰ类整合酶阳性株ERIC-PCR分为59个基因型。结论在复方磺胺甲噁唑的耐药基因分布中,dfrA17、sul2、sul1携带率较高。在耐药性播散方面,耐药基因的水平转移比菌株克隆传播作用更大。

Study on the resistance related genes of trimethoprim-sulfamethoxazole in urinary isolates of Escherichia coli

Objective To investiage the distribution of resistance related genes of trimethoprim-sulfamethoxazole in urine isolates of Escherichia coll. Methods 145 isolates of Escherichia coli were isolated from urine sample, the Trimethoprim and sulfamethoxazole susceptibility test of which were performed by K-B method. PCR for class Ⅰ and Ⅱ integrons were performed in trimethoprim-resistant isolates. Integron PCR products were digested with Hinf I ,and amplicons with the same RFLP pattern were deemed to contain the same gene cassettes. The PCR products which is representative for each pattern were selected for DNA sequencing. The DNA sequences were analysed with BLAST algorithm in GenBank. sul1, sul2 and sul3 were detected by PCR in sulfamethoxazole-resistant isolates. ERIC- PCR were performed for genotype of intI-postive isolates. Results The resistant rate to trimethoprim and sulfame- thoxazole were 73.1% and 79.1 %, respectively. In 109 trimethoprim-resistant isolates, 8 different gene cassettes of integrons and 4 different dfrA genotypes were found. In 119 sulfamethoxazole-resistant isolates, sull （72 isolates）, sul2 （82 isolates） and sul3 （2 isolates） were detected. In 80 intl-postive isolates, 59 genotypes were detected by ERIC-PCR. Conclusion DfrA17,su12 and sull are widespread in urine isolates of Escherichia coli with risistance to trime-thoprim-sulfamethoxazole. Horizontal gene transfer plays a more important role than clonal expansion in the dissemi nation of the durg-resistance to trimethoprim-sulfamethoxazole.