阴沟肠杆菌的耐药性分析及其耐药机制研究

Drug resistance of Enterobacter cloacae and its drug resistance mechanisms

目的了解某院临床分离阴沟肠杆菌耐药基因分布及流行情况,为临床合理用药提供参考。方法收集2008年1月-2011年6月自临床感染患者分离的114株阴沟肠杆菌进行细菌鉴定和药敏试验,了解产酶阴沟肠杆菌的流行情况。结果未检出碳青霉烯酶基因,34株阴沟肠杆菌广谱β-内酰胺酶基因阳性,其中18株携带ESBLs基因,47株阴沟肠杆菌质粒AmpC酶基因阳性;共检出26株Ⅰ类整合子基因阳性菌株,其中23株可变区扩增阳性,共扩增出4种耐药基因盒,aadB-aadA2(1000bp)17株,dfrA15(700bp)4株,aadA1(1 000bp)2株;产酶菌株呈现多药耐药现象;15株产CTX-M基因阴沟肠杆菌接合试验成功;ERIC分型结果显示,63株产酶菌株为11种不同克隆株。结论 AmpC酶、广谱β-内酰胺酶和Ⅰ类整合子广泛分布于临床分离阴沟肠杆菌中,在阴沟肠杆菌多药耐药机制中起重要作用;阴沟肠杆菌对碳青霉烯类抗菌药物的敏感性降低或耐药,主要与其携带AmpC酶和ESBLs有关,且院内存在产酶菌株的散在克隆传播现象。

OBJECTIVE To understand the distribution and prtevalence of drug resistance genes in clinical isolates of Enterobactercloacae so as to guide the reasonable clinical use of antibiotics. METHODS Totally 114 strains of E. cloacae were isolated from the patients with infections ,who were treated from Jan 2008 to Jun 2011, then the bacteria identification and drug susceptibility testing were performed, arid the prevalence of enzyme-producing E. cloacae was analyzed. RESULTS No carbapenemase genes have been detected; broad spectrum β-lactamase genes were tested positive in 34 strains of E, cloacae, among which 18 strains carried ESBLs genes;47 strains of E. clacae were tested positive for plasmid AmpC enzyme gene. Totally 26 strains have been detected positive for carrying type I integron gene, among which 23 strains were with variable regioa amplified positive, totally 4 types of drug resistance gene cassettes have been amplified, including aadB-aadA2（1 000 bp） in 17 strains, dfrA15 （700 bp） in 4 strains, and aadAl（1 000 bp） in 2 strains. The enzyme-producing strains were multidrug-resistant; the conjugation experiment of 15 strains of CTX-M gene-producing E. cloacae succeeded, the result of the ERIC genotyping indicated that the 63 strains of enzyme-producing strains were defined as 11 clones. CONCLUSION The AmpC enzyme, broad spectrum β-lactamase, and type I integron widely distribute in the clinical isolates of E. cloacae and play an important role in the muhidrug-resistant mechanisms; the drug resistance of the E. cloacae to carbapenems is mainly related to AmpC enzyme and ESBLs genes, and the clones of the enzyme-producing strains have disseminated in the hospital.