产超广谱β内酰胺酶大肠埃希菌与肺炎克雷伯菌的基因型和耐药性分析

目的研究我院住院患儿分离产ESBLs大肠埃希菌及肺炎克雷伯菌的基因型及其相关耐药性分析。方法收集2004年10月-2005年10月我院住院患儿呼吸道分离产ESBLs大肠埃希菌75株，肺炎克雷伯菌45株，PCR限制性片段长度多态性（RFLP）分析及PCR产物克隆测序等方法明确ESBLs基因型，并结合体外抗生素敏感试验研究基因分型与细菌对不同头孢菌素及氨曲南的敏感性的关系。结果上述120株细菌中112株（93．3％）产CTX—M型p内酰胺酶；未能扩增出SHV型、TEM型ESBL基因。CTX—M型基因亚型主要为CTX—M9簇中的CTX—M-14型（78、6％），其次为CTX—M-1簇中的CTX—M-3型（19．6％），仅有1．8％为CTX—M-8型；携带CTX-M-1簇的菌株对头孢他啶、头孢哌酮-舒巴坦、阿莫西林-克拉维酸、头孢吡肟及氨曲南的耐药率均明显高于CTX—M-9型。结论CTX—M基因型为武汉地区儿童分离大肠埃希菌以及肺炎克雷伯菌中最常见的ESBLs，CTX—M-14为最常见基因型，其次为CTX—M-3型；CTX—M-9簇及CTX-M-1簇对头孢他啶、头孢吡肟、头孢哌酮-舒巴坦和氨曲南的水解能力差异明显。

Genotype analysis of extended-spectrum β-lactamases in Escherichia coli and Klebsiella pneumoniae isolates from Wuhan area and its relation to antibiotic resistance

Objective To study the genotype distribution of extended spectrum β-1actamases in E. coli and K. pneumoniae isolated from children in Wuhan area and to explore its relation to antibiotic resistance. Methods Consecutive nosocomial isolates of extended-spectrum β-1actamases （ESBLs） producing E. coli （75） and K. pneumoniae （45） were collected during the period from Oct 2004 to Oct 2005 in Wuhan Children＇s Hospital. PCR-restriction fragment length polymorphism analysis, gene cloning and DNA sequencing were used for ESBLs genotyping. Susceptibility testing was done to analyze the relationship between ESBLs genotype and antibiotic resistance. Results One hundred twelve isolates carried the genes for CTX M-type lactamases, including CTX-M-1 cluster （mainly CTX-M-3, 19.6%） and CTX-M-9 cluster （mainly CTX-M-14, 78.6%）. CTX M-8 genotype was identified in only l. 8%o of the CTX-M-type positive isolates. The resistance rate of isolates carrying CTX-M-I cluster to ceftazidime, ampicillin-clavulanate, cefoperazone-sulbactam, cefepime and aztreonam was higher than those carrying CTX- M-9 cluster genes. Conclusions CTX-M is the predominant extended-spectrum β-lactamase genes in E. coli and K. pneumoniae isolated from children in Wuhan. CTX-M-14-type is the most common CTX-M genotype, followed by CTX-M-3-type. There is remarkable difference between CTX-M-I and CTX-M-9 cluster enzymes in the ability to hydrolyze ceftazidime, ampicillin-clavu- lanate, cefoperazone-sulbactam, cefepime and aztreonam.