质粒介导aac(6')-Ib基因检测与喹诺酮类耐药

A study of plasmid-mediated aac(6′)-Ib gene determination and quinolone resistance

目的了解大肠埃希菌临床株对喹诺酮类抗菌药物耐药情况并分析质粒介导aac(6')-Ib基因存在与喹诺酮类药物耐药性的关系。方法采用纸片扩散法(K-B)对临床中段尿分离所得121株大肠埃希菌进行耐药性检测,聚合酶链反应(PCR)法检测大肠埃希菌aac(6')-Ib基因,对aac(6')-Ib基因阳性菌株扩增片段进行DNA测序并确定基因型。结果大肠埃希菌临床株对萘啶酸、环丙沙星、诺氟沙星、左氧氟沙星4种喹诺酮类抗菌药物耐药率均高于75%。aac(6')-Ib基因检出率为14.0%(17/121),经DNA测序确定aac(6')-Ib基因变异体(cr)有14株,突变率为82.4%(14/17);aac(6')-Ib基因阳性株对氨苄西林-舒巴坦、哌拉西林-他唑巴坦、头孢唑啉、头孢克洛、头孢呋辛、阿米卡星、环丙沙星、诺氟沙星、左氧氟沙星耐药率高于阴性株且差异有统计学意义(P<0.05)。结论仁济医院临床分离大肠埃希菌对喹诺酮类抗菌药物耐药情况严重;质粒介导aac(6')-Ib基因的存在可使大肠埃希菌对喹诺酮类抗菌药物耐药性提高;质粒介导aac(6')-Ib基因还可能引起细菌对β-内酰胺酶抑制剂药物和头孢菌素类药物敏感性下降。

Objective To investigate the quinolone resistance to Escherichia coli isolates, and to identify the relationship of existence of plasmid-mediated aac （6＇） -Ib genes with the resistance of quinolones. Methods Kirby- Bauer（k-B） method was performed for 121 Escherichia coli isolates from urine samples collected from March 2010 to March 2011 in Renji Hospital. The aac （6＇）-Ib genes in Escherichia coli isolates were determined by polymerase chain reaction（PCR）. The amplification fragment of positive isolates were selected to be sequenced, and the genotypes were determined. Results Escherichia coli isolates＇ resistance rates of nalidixic acid, ciprofloxacin, norfloxacin and levofloxacin were all higher than 75%. The determination rate of aac（6＇）-Ib gene was 14.0% （ 17/121 ）, and the mutation rate was 82.4% （14/17）. The aac （6＇）-Ib gene positive isolates had higher resistance rates of ampicillin- sulbactam, piperacillin-tazobactam, cefazolin, cefaclor, cefuroxime, amikacin, ciprofloxacin, norfloxacin and levofloxacin than the negative isolates. There was statistical significance （P 〈 0. 05 ）. Conclusions Quinolone resistance to Escherichia coli isolates in Renji Hospital is serious. With the plasmid-mediated aac （6＇）-Ib genes, the Escherichia coli isolates may have an increasing resistance rates to quinolones and decreasing susceptibility to beta-lactamase inhibitors and cephalosporins antibiotics.