同一标本分离的2株碳青霉烯类耐药肠杆菌科细菌耐药机制相关性分析

The relationship of resistance mechanism of two strains of Enterobacteriaceae resistant to carbapene-ms isolated from a single specimen

目的对从同一标本中分离的碳青霉烯类药物耐药的肺炎克雷伯菌和摩根摩根菌进行耐药机制相关性分析。方法琼脂稀释法进行药物敏感试验；特异性PCR扩增和序列分析检测介导耐碳青霉烯类药物的相关基因；接合试验、质粒提取和耐药基因周围序列分析耐药的可传递件、耐约质粒的同源性及耐药基因的遗传背景；提取外膜蛋白分析菌株外膜蛋白的改变。结果2株分离菌均产碳青霉烯酶并扩增出介导碳青霉烯类耐药的KPC-2型基因；质粒接合试验成功传递了对碳青霉烯类药物的耐药性，耐药基因被携带在2个大小不同但耐药基因周围序列完全相同的质粒上；其中摩根摩根菌耐药株缺失了相对分子质量约为38×10^3的外膜蛋白同时出现36×10＾3的外膜蛋白而肺炎克雷伯菌则缺失了外膜蛋白OMPK36。结论2株分离菌均携带KPC-2基因。该基因由2个大小不同的质粒携带，同一复合转座子介导了KPC－2基因在2株细菌的不同质粒上转移。同时外膜蛋白缺失参与丁对碳青霉烯类抗生素耐药。

Objective To investigate the relationship of resistance mechanisms of a KlebsieUa pneumoniae strain and a Morganella morganii strain resistance to carbapenems isolated from a single specimen. Methods Sensibility of antimicrobial agents was detected by agar dilution method. Specific PCR and DNA sequence analysis were performed to detect resistance genes. Plasmid feature was detected by plasmid conjugation and electrophoresis analysis. Genetic environment around blaKpC was analyzed with sequencing. The changes of outer membrane permeability were analyzed with electrophoresis of outer membrane proteins. Results blakpc-2 was detected in 2 original isolates strains and their transconjugants. Carbapenem-resistance was successfully transfered by conjugation experiments, blaKPC-2 was located on dissimilar plasmids, but genetic environment around blaKPc-2 was the same sequence. The Morganella morganii isolate showed a loss of 38× 10^3 OMPs and an additional 36 × 1063 OMPs appearance, while the Klebsiella pneumoniae isolate showed a loss of OMPK36. Conclusion blaKpc-2 was detected in 2 isolates. This gene encoded by two plasmids with different sizes was located on the same composite transposon. The lack of outer membrane proteins could also play an important role causing isolates to exhibite resistance to carbapenems.