目的研究2株产气肠杆菌临床株Ea293和Ea2880对厄他培南耐药的机制。方法采用微量肉汤稀释法测定最低抑菌浓度（MIC）,应用KB法检测菌株对美罗培南、亚胺培南及厄他培南的耐药性，改良Hodge试验检测碳青霉烯酶；聚合酶链反应（PCR）扩增碳青霉烯酶基因（KPC，IMP1、2组，VIM）和广谱及超广谱β内酰胺酶基因(TEM，SHV，CTXM1、2、9组ESBLs),并进行序列分析；十二烷基硫酸钠聚丙烯酰胺凝胶电泳（SDSPAGE）进行细菌外膜蛋白分析，并对外膜蛋白基因OmpE36进行PCR扩增及序列分析。结果药物敏感试验显示，产气肠杆菌Ea293和Ea2880均对厄他培南耐药。PCR扩增4种碳青霉烯酶基因和5种广谱及超广谱β内酰胺酶基因,仅Ea2880的SHV和CTXM9组ESBLs基因阳性，SHV基因的PCR产物测序为SHV11型广谱酶。细菌外膜蛋白SDSPAGE结果显示，与碳青霉烯类抗生素敏感的产气肠杆菌Ea1885相比，Ea293和Ea2880均缺失42 kD左右的条带,即OmpE36。PCR扩增外膜蛋白基因OmpE36，Ea2880可见预期片段，DNA序列分析显示其与GenBank公布的产气肠杆菌标准株ATCC 13048的相似性为87%，氨基酸序列的相似性亦为87%；而Ea293未扩增出预期片段。结论产气肠杆菌临床株Ea293与Ea2880对厄他培南耐药的主要原因可能是外膜蛋白基因OmpE36缺失，同时Ea2880可能还有CTXM9组ESBLs参与。
ObjectiveTo study resistant mechanisms of two clinical strains of Enterobacter aerogenes (Ea293 and Ea2880)to ertapenem. MethodsThe minimum inhibitory concentrations (MICs) of antimicrobial agents were determined by microbroth dilution method, drug resistance of strains to imipenem，meropenem，and ertapenem were determined by KB test; carbapenemase was confirmed by modified Hodge test, carbapenemase genes（KPC，IMP1 group，IMP2 group，VIM）, broadspectrum and extendedspectrum βlactamases genes（TEM，SHV，CTXM1 group，CTXM2 group，CTXM9 group） were amplified by polymerase chain reaction (PCR), and sequences were analysed; Outer membrane protein (Omp) was analyzed by sodium dodecylsulfatepolyacrylamide gel electrophoresis (SDSPAGE) and the coding gene OmpE36 was amplified by PCR. ResultsAntimicrobial susceptibility test showed that Ea293 and Ea2880 were all resistant to ertapenem. Among amplified 4 carbapenemase genes and 5 broadspectrum and extendedspectrum genes, only blaSHV and blaCTXM9 group ESBLs in Ea2880 were positive, BlaSHV DNA sequence was SHV11 type. SDSPAGE showed that compared with ertapenemsensitive isolate Ea1885, ertapenemresistant isolate Ea293 and Ea2880 lacked the protein band with 42kD which might be the outer membrane protein gene OmpE36. OmpE36 was amplified by PCR, Ea2880 appeared the excepted bands, but Ea293 didn’t. The similarity of DNA and amino acid sequences of OmpE36 of Ea2880 with the standard Enterobacter aerogenes ATCC13048 from GenBank were both 87%.ConclusionThe resistance of clinical strains of Enterobacter aerogenes Ea293 and Ea2880 to ertapenem might be associated with the loss of outer membrane protein gene OmpE36. Furthermore，Ea2880 might be associated with production of CTXM9 group ESBLs.