临床产多种β-内酰胺酶大肠埃希菌的生物学研究

Multiple β-Lactamases Producing Clinical Isolates of Escherichia coli

目的对临床分离出产多种β-内酰胺酶的大肠埃希菌,进行生物学以及耐药特性研究。方法用三维试验、等电聚焦以及酶抑制试验以及接合试验,对临床分离的1株对多种β-内酰胺类抗生素高度耐药的大肠埃希菌进行分析,用E-TEST法进行最小抑菌浓度(MIC)测定。结果该菌株三维试验为阳性显示高产AmpC酶,等电聚焦以及酶抑制试验表明,该菌株能够产3种等电点(PI)分别为5.4、8.2及9.0的β-内酰胺酶,等电点为9.0的β-内酰胺酶能够被氯唑西林抑制,而不能被克拉维酸抑制;等电点为8.2和5.4的β内酰胺酶能够被克拉维酸抑制而不能被氯唑西林抑制,而且接合实验表明这两种酶的特性可以被转移到受体菌;检测表明该菌株对环丙沙星、阿米卡星、青霉素类、酶抑制剂合剂、三代头孢菌素类甚至头孢吡肟耐药,但对碳青酶烯类的亚胺培南和伊他培南均敏感。结论我院临床分离大肠埃希菌中已经出现同时产AmpC、ESBLs等多种广谱β内酰胺酶的菌株,并造成对多种三代头孢菌素及头孢西丁耐药,对临床的抗生素治疗带来严重威胁。

OBJECTIVE To study the biologly and resistance character of multiple β-lactamases producing clinical (isolates) of Escherichia coli. METHODS β-Lactams highly resistant clinical isolates of E. coli were studied by three-dimensional methods, isoelectric focusing (IEF) and conjugation experiment. Then the MIC of this strain was (examined) by E-stripe. RESULTS This isolate was showed as high AmpC producing by three-dimensional method. And then, IEF found that this strain could produce three β-lactamases which PI was (5.4,) (8.2) and (9.0,) respectively. The β-lactamase whose PI was 9.0 could be inhibited by cloxacillin but not by clavulanate and that whose PI was (8.2) and (5.4) could be inhibited by clavulanate but not by cloxacillin. The conjugation experiment (indicated) that the gene of the β-lactamase whose PI was (8.2) could be transferable. The strain was resistant (to ciprofloxacin), amikacin and most of penicillins, cephalosporins, β-lactams combined with the β-lactams (inhibitors) and even cefepime. It was susceptible to imipenem and etrapenem. CONCLUSIONS The E. coli strains simultaneously producing AmpC, ESBLs and other broad spectrum β-lactamases have been isolated clinically in our hospital. They are resistant to many penicillins, cephalosporins and cefomycins and have brought us great menace in antibiotic therapy.