老年患者大肠埃希菌产质粒AmpC酶基因型特点及耐药性分析

Genotype characteristics and analysis of the drug resistance in Escherichia coli producing plasmid-mediated AmpC β-lactamases in the elderly patients

目的了解临床分离老年患者大肠埃希菌产质粒AmpC酶的基因型及其耐药(DR)性特点,为临床合理选用抗生素提供依据。方法收集2009年度老年患者临床不重复分离大肠埃希菌233株,用三维试验和确证试验分别进行羟氨苄青霉素(AmpC)酶和超广谱β内酰胺酶(ES-BLs)检测,用接合试验证实酶基因型的转移,通过PCR检测及序列分析进行质粒AmpC酶基因型确定,采用药敏纸片扩散法(K-B法)进行药敏试验。结果 233株大肠埃希菌中,头孢西丁抑菌环直径≤17mm的有53株,占22.7%,酶提取物三维试验检测7株阳性,4株(1.7%)PCR扩增出CMY-2型质粒AmpC酶,有1株接合试验阳性;ESBLs阳性占68.7%(160/233)。药敏结果显示产质粒AmpC酶大肠埃希菌对二、三代头孢菌素、氨曲南、头孢西丁和含酶抑制剂的DR率明显高于非产酶株(P<0.05),所有大肠埃希菌对亚胺培南和美罗培南均100%敏感。结论从老年患者中成功分离出产CMY-2型质粒AmpC酶大肠埃希菌,产质粒AmpC酶菌株对β-内酰胺类抗生素的耐药性明显高于非产酶株。

Objective To understand the genotype characteristics and drug resistance （DR） in Escherichia coli producing plasmid-mediated AmpC β-lactamases in the elderly patients so as to guide the rational use of antibiotics in clinical.Methods 233 strains of E.coli isolated from the elderly patients in the 8 hospitals in 2009 were collected.Three-dimensional test and certified test were used to detect AmpC and ESBLs;conjugation experiment were used to verify the transitivity of genotype.PCR amplification test and screening analysis were performed to confirm the genotype of plasmid-mediated AmpC β-lactamases;Disk diffusion susceptibility （K-B method） was adopted to detect drug sensitive test.Results Among 233 Escherichia strains,there were 53 Escherichia strains of which Cefoxitin inhibition zone was equal to or below 17 mm （22.7%）,7 positive strains of three-dimensional test from the enzymic extraction of which there were 4 strains producing CMY-2 type AmpC（1.7%）;the drug-sensitivity data showed that the resistance to the second and third generation cephalosporins,aztreonam,cefoxitin and containing enzyme inhibitors were significantly higher than those of the no enzymic strains（P0.05）.All the strains of Escherichia colis were sensitive to meropenem and imipenem.DR rate to 12 antibiotics of these strains producing enzyme （AmpC alone,ESBLs only,both plasmid AmpC and ESBLs） or not had statistically significant differences （P0.05）.Non-lactamase producing strains remained at a high sensitivity rate to 15 kinds of antibiotics;DR rate of the AmpC-producing strains to the second and third generation cephalosporins,aztreonam and cefoxitin was up to 100%.However,these strains showed a high sensitivity rate to cefepime and carbapenems;ESBLs-producing strains also showed high resistance to the third and fourth generation cephalosporins and aztreonam and other antibiotics,but they were mostly sensitive to carbapenem,enzyme inhibitors and cefoxitin.Both AmpC and ESBLs producing strains increased DR rate to other antibiotics except meropenem and imipenem （sensitive） significantly.Conclusions The resistance of Escherichia coli to β-lactam antibiotics mainly includes the production of ESBLs and AmpC,the enzyme production strains can be selected carbapenem on the basis of clinical experience.