对碳青霉烯类抗生素敏感性下降的肠杆菌科细菌耐药机制的研究及流行病学调查

Study on resistance mechanisms and epidemiology of Enterobacteriaceae with decreased carbapenem susceptibility

目的对临床分离的碳青霉烯类抗生素耐药的肠杆菌科细菌进行耐药机制研究及流行病学调查。方法收集2010年1月至2010年8月，对碳青霉烯类抗生素敏感性下降的肠杆菌科细菌18株，全自动微生物鉴定仪检测细菌对常见抗生素最低抑菌浓度（MIC），纸片法检测细菌产超广谱-内酰胺酶、头孢菌素酶、碳青霉烯酶的情况，并用PCR扩增、DNA测序确定所产碳青霉烯酶基因型。脉冲场凝胶电泳对耐药菌进行同源性分析。结果8株耐药菌全部检出ESBLs酶、AmpC酶，17株检出KPC-2酶，3株EDTA纸片法阳性提示产其他金属碳青霉烯酶，其中两株合并产KPC-2。脉冲场凝胶电泳结果显示15株肺炎克甫们菌分为6种带型。结论KPC-2碳青霉烯酶是造成肠杆菌科细菌对碳青霉烯类抗生素敏感性下降的主要原因，并在我院局部短暂流行，携带KPC-2基因的临床菌株同时携带多种耐药基因。

Objective To investigate the resistance mechanisms and epidemiology of Enterobacte- riaceae isolated from clinical with reduced susceptibility to imipenem or meropenem. Methods 18 strains of Enterobacteriaceae with reduced carbapenem susceptibility were collected during January to August in 2010. The MICs of these strains were determined using automated microbial identification system. ESBLs, AmpC and KPC were tested using the agar dilution method. PCR amplification and DNA sequence were performed to analyze the KPC genes, PFGE was used to examine the molecular epidemiology. Results All 18 strains were detected ESBLs and AmpC, 14 strains were detected KPC-2. 3 strains with EDTA paper method posi- tive may produce other metal carbapenem, in which 2 strains harbor KPC-2. PFGE types indicate that there were six genotypes among 15 strains of KlebsieUa pneumoniae. Conclusion Plasmid-mediated KPC-2 was the main reason which makes Enterobacteriaceae reducing carbapenem susceptibility and causes short-term epidemic in hospital. Clinical strains harboring KPC-2 gene may carry multiple resistance genes meanwhile.