产AmpC酶大肠埃希菌和肺炎克雷伯菌中整合子与多重耐药的研究

Integron-mediated multi-resistance in AmpC beta-lactamase from clinical isolates of Esecherichia coli and Klebsiella pneumoniae

目的探讨整合子介导的耐药机制在产AmpC酶大肠埃希菌和肺炎克雷伯菌多重耐药中的作用。方法5株产AmpC酶大肠埃希菌和肺炎克雷伯菌分离自2002年1月—2004年5月间我院呼吸科住院的患者,采用E-test试验条进行药敏试验、电转化试验,筛选、分离耐药质粒。PCR扩增Ⅰ型整合子基因盒插入序列,分子克隆和序列分析。结果所有产酶菌株通过电转化试验可将头孢西丁耐药性传递给受体菌,5个产AmpC酶耐药质粒中,有4个检出整合酶序列,其中3个携带2种抗药性基因盒,包括氨基糖苷乙酰转移酶基因aacA4;氨基糖苷腺苷转移酶基因aadA5;二氢叶酸还原酶基因dfrA17;氯霉素外排蛋白编码基因cmlA4。结论整合子介导的抗药性基因盒参与了产质粒AmpC酶大肠埃希菌和肺炎克雷伯菌多重耐药的形成,应引起高度重视。

Objective To investigate integron-mediated multi-resistance in AmpC beta-lactamase from clinical isolates of Esecherichia coli and Klebsiella pneumoniae. Methods Five strains of Esecherichia coli and Klebsiella pneumoniae producing AmpC beta-lactamase were isolated from patients bespitalized in respiratory ward from January 2002 to May 2004. Antibiotics sensitivity was detected by E-test method, electroporation, and multiresistance plasmids were screened and isolated by extracting transfonnant plasmids. Inserted gene cassettes of class 1 integron were amplified and analyzed by PCR and DNA sequencing. Results All 5 strains of Klebsiella pneumoniae and Esecherichia coli producing AmpC beta-lactamase transferred cefoxitin-resistance to recipient by electro- poration. In four of them AmpC beta-lactamase-producing plasmids were determined as class 1 integron sequence, of 3 harbored 2 drug resistance gene cassettes encoding resistance to aminoglycnsides（ aacA4 and aad45）, trimetbeprin （ dfiA17）and chloramphenicel （cmlA4）. Conchusion More attention should be paid to integron which plays an important role in multi-resistance from plasmid-mediated AmpC beta-lactamase.