外科监护室耐药大肠杆菌和肺炎克雷伯杆菌产超广谱β-内酰胺酶的基因型研究

目的:了解外科监护室产生超广谱β-内酰胺酶(extended-spectram β-lactamases,ESBLs)的大肠杆菌和肺炎克雷伯杆菌的耐药性和基因型.方法:琼脂稀释法测定临床分离株的最小抑菌浓度(minimal inhibitory concentration,MIC)值,分别用TEM、SHV和CTX-M的特异性引物扩增临床菌株和接合子的超广谱β-内酰胺酶基因.接合试验提取接合子质粒进行聚合酶链反应(polymerase chin reaction,PCR),产物测序,确定基因类型.结果:93.5%的菌株含CTX-M基因,38.7%的菌株含SHV基因,87.1%的菌株含TEM基因.测序明确了TEM-1,CTX-M-1,3,14,22等基因类型.结论:外科监护室大肠杆菌和肺炎克雷伯杆菌产超广谱β-内酰胺酶的基因以CTX-M为主.

Genotype of extended-spectrum β-lactamases produced by antibiotic-resistant Escherichia coli and Klebsiella pneumoniae in surgical intensive care unit

OBJECTIVE:To describe the antibiotic resistant mode of extended-spectrum beta-lactamases(ESBLs) producing Escherichia coli (E. coli.) and Klebsiella pneumoniae (KPn) in surgical intensive care unit(SICU), and to implore the molecular epidemiology of ESBLs coding genes of these strains. METHODS: The minimal inhibitory concentrations (MICs) at antibiotics were examined by agar dilution method. The ESBLs coding genes were amplified by TEM, SHV and CTX-M specific primers. Amplicons of such genes with conjugates' plasmids as templates were sequenced. RESULTS: In vitro susceptibility tests of ESBLs producing strains showed a high level of resistance to most of the beta-lactam biotics, especially cefotaxime. 93.5% of these ESBLs positive strains contained CTX-M group genes,and 38.7% of the strains contained SHV genes. By sequencing, some genotype were determined: TEM-1, CTX-M-1,3,14,22. CONCLUSION: ESBLs producing strains were resistant to most of the beta-lactam biotics. The most prevalent ESBLs genotype of ESBLs produced by E coli and KPn in SICU was CTX-M subgroup. The most probable reason might be the extensive use of cefotaxime.