威海市区CTX-M型具有头孢他啶水解活性的ESBLs基因型调查  

Research of CTX-M-type ceftazidime hydrolyzing ESBLs in Weihai

作　　者：王喜仁[1] 赵淑堂 孙耀峰[1] 

机构地区：[1]威海市立医院检验科,威海市264200 [2]威海卫人民医院心血管内科,威海市264200

出　　处：《实用检验医师杂志》2013年第4期205-209,共5页Chinese Journal of Clinical Pathologist

摘　　要：目的 调查威海市区具有头孢他啶（ceftazidime,CAZ）水解活性的头孢噻肟（cefotaxime,CTX）M型产超光谱β-内酰胺酶（extended-spectrum β-lactamases,ESBLs）基因型,了解其种类、比例、传播机制以及对CAZ的耐药特点,评估目前CAZ药敏折点对产CTX-M型ESBLs菌株的影响.方法 对威海市区3家医院2012年临床分离的产ESBLs的120株大肠埃希菌（Escherichia coli,E.coli进行研究,采用特异性引物扩增TEM、SHV、CTX-M系列基因,测序后进行序列分析；挑选产生单一ESBLs基因型的菌株,采用琼脂稀释法测定其对CTX、CAZ的最小抑菌浓度（minimal inhibitory concentration,MIC）值；接合实验了解具有CAZ活性的CTX-M型ESBLs编码基因所在质粒是否为接合性质粒,以及接合子的MIC范围.结果 120株ESBLs E.coli中检出产生blaCTX-M-55的E.coli共40株（33.3％）,产生blaCTX-M-15型者26株（21.7％）,产生blaCTX-M-101及blaCTX-M-123型分别为2株（1.7％）和3株（2.5％）,这四种基因型共占71株（59.2％）.基因序列分析表明,这四种基因在725位有1个碱基的差异（GAC→GGC）,导致240位氨基酸由天冬氨酸变为甘氨酸.产单一基因型blaCTX-M-15、55、101和123的菌株共55株.药敏试验结果显示,上述55株ESBLs大肠埃希菌对CTX均耐药,对CAZ的MIC值范围为8～128 μg/mL,耐药率为74.5％（41/55）.接合实验发现,上述4种基因可以通过接合而传递耐药性.其接合子对CAZ、CTX的MIC值较亲本降低1～8倍,接合子对CTX均耐药,对CAZ的MIC值范围为4～128 μg/mL,耐药率为22.8％（8/35）.结论 威海市区大肠埃希菌产生的具有CAZ水解活性的ESBLs基因型主要为blaCTX-M-55,其次为blaCTX-M-15,blaCTX-M-101和blaCTX-M-123较少.耐药基因所在的质粒为可接合性质粒.blaCTX-M-15、55、101、123型ESBLs基本适合目前的CLSI CAZ折点,可直接向临床报告药敏结果.鉴于可水解CAZ的CTX-M型ESBLs在临床菌株中检出率较高,对于治疗表型敏感的ESBLs�Objective To research the genotype, proportion, disseminative mechanism and ceftazidime （CAZ） resistance of CAZ hydrolyzing eefotaxime （CTX） M type extended-spectrum 13-1actamases （ESBLs） produced by Escherichia coli （E.coli） in Weihai. Methods 120 non-duplicate clinical isolates of ESBLs producing E.coli were studied, which collected from several hospitals in Weihai from January 2012 to June 2012. PCR analysis was used to amplify TEM, SHV, CTX genes, sequence analysis was performed to identify ESBLs genotype, disseminative mechanism was investigated by conjugation experiments. Minimal inhibitory concentration （MIC） was used to determine the sensitivity of antibiotics by agar dilution for strains and their transeonjugants only producing a single ESBLs genotype. Results A totle of 71 isolates produced CAZ hydrolyzing ESBLs in 120 strains ESBLs producing E.cloi, including blaCTX-M-55, blaCTX-M-15, bIaC- TX-M-101 and blaCTX-M-123, the positive rate was 33.3%, 21.7%, 1.7% and 2.5% respectively. Sequence analysis indicated that GAC--GGC substitution of 725th caused aspartic acid to glycine in 240 th were occurred in the four ESBLs genes. There were 55 strains produced single blaCTX-M-15,55,101 and 123. They were all on drug resistant of CTX, and MIC of these strains against CAZ range from 8 ug/mL to 128 ug/mL. Conjugation test revealed that plasmids harbouring the resistance genes could be transmitted to receptor baeteria. The MIC of transconjugants to CTX and CAZ were 1 to 8 fold lower than that of donor strains. These transconjugants were all on drug resistant of CTX. The range of MIC on CAZ was 4-128 ug/mL, and drug resistance rate was 22.8% （8/35）. Conclusion The most prevalent genotypes of CTX-M hydrolyzing CAZ in Weihai are blaCTX-M-55, followed by blaCTX-M-15, blaCTX-M-101 and blaCTX-M-123 accounted for fewer percentage of CTX-M CAZ hydrolyzing ESBLs. The plasmid harbouring CAZ resistant genes are conjugative plasmid. The four genotype of ESBLs are in accordance with current CAZ breakpoi

关 键 词：头孢他啶 CTX-M-15 CTX-M-55 CTX-M-123 接合性质粒 大肠埃希菌 

分 类 号：R446.5[医药卫生—诊断学]