阴沟肠杆菌AmpC β-内酰胺酶由诱导型转变为组成型的机制  

The mechanism of AmpC β-lactamase change from inducible type to constitutive type

作　　者：涂婉[1] 赵虎[1] 

机构地区：[1]复旦大学附属华东医院检验科,上海200040

出　　处：《复旦学报（医学版）》2010年第2期189-193,共5页Fudan University Journal of Medical Sciences

基　　金：上海市科委重点科研基金项目(054119509)

摘　　要：目的研究质粒传播和ampD基因突变两种机制对阴沟肠杆菌AmpC β-内酰胺酶由诱导型转变为组成型的影响作用和比率。方法收集医院感染患者标本,将诱导型阴沟肠杆菌和其转变后的组成型阴沟肠杆菌分为一组。对每组细菌的质粒ampC基因和染色质ampD基因进行扩增、测序和序列比对。结果195例感染拟似诱导型阴沟肠杆菌患者中,25例(12.82%)的菌株转变为组成型。其中,10组菌株的阳性转变为单纯的质粒传播所致,10组为单纯的ampD基因突变所致,1组既有质粒传播又存在ampD基因突变,另外4组则两者全无。12株转变的组成型阴沟肠杆菌ampD基因存在有意义的突变位点,其中7株存在移码突变,另外5株为点突变。结论阴沟肠杆菌由诱导型转变为组成型已经达到较高的比率,质粒传播和染色质突变均为引起这种转变的重要原因。质粒介导的AmpC酶已经跨种、跨区域传播,染色质ampD基因的突变率也远远高于其自然突变率,这两种机制均应在临床医疗中得到足够的重视。Objective To investigate the influence of plasmid spread and ampD mutation to Enterobacter cloacae that leads to the AmpC β-lactamase change from inducible type to constitutive type. Methods The Enterobacter cloacae were isolated from the patients with nosocomial infection. The inducible type isolations and their constitutive type changers were put into the same group. The plasmid ampC gene and chromatin ampD gene in pairs in each group were amplified, sequenced and compared. Results Of 195 patients infected by Enterobacter cloacae of inducible type, 25 （12.82%） were changed to the ones of constitutive high type. In these 25 changed groups, 10 were caused by plasmid spread, 10 by ampD mutation, 1 by both, and 4 by neither. Twelve changed constitutive type strains had ampD significant mutations, in which 7 were frame-shift mutations and 5 were spot mutations. Conclusions The change ratio of Enterobacter cloacae from inducible type to constitutive type is rather high. Both plasmid spread and ampD mutation are possibly the mechanism of such change. Plasmid mediated AmpC β-lactamase spreads among different species and interregionally. The mutation rate of chromatin ampD gene is also higher than the natural mutation rate. These two mechanisms should be considered in clinical treatment.

关 键 词：AMPCΒ-内酰胺酶 组成型 质粒传播 染色质突变 ampD基因 

分 类 号：R378.2[医药卫生—病原生物学]