摘要
目的分析临床分离的高产AmpC酶大肠埃希菌(E.coli)中染色体ampC基因启动区突变状况。方法选择三维酶试验产AmpC酶和/或产ESBLs以及头孢西丁耐药的40株E.coli,用聚合酶链反应(PCR)扩增质粒型ampC基因和ampC基因启动区的片段,启动区扩增产物用MaeⅢ内切酶酶切。参考以上结果,选择部分菌株的启动区扩增产物测序分析。结果40株菌中,12株MaeⅢ酶不能切开启动子的-35区。21株被测序菌中,5株酶切异常的菌株,在-35区均出现-32位上T→A突变;11株在衰减区出现突变,主要突变点分布在+22位、+26位、+27位和+32位;3株出现-42、-18、-1和+584个位点突变,-42位C→T突变形成了与-35区强启动子相同的6位体序列。结论-42位、-32位和衰减区茎环位点的突变增强ampC基因的转录,在大肠埃希菌对广谱头孢菌素类药物耐药中起重要作用。
Objective To investigate mutations on AmpC promoter and attenuator in clinical isolates of Escherichia coil Methods Forty Escherichia coil isolates producing AmpCβ-1aetamases and/or ESBLs with three-dimensional extract test and being resistant to cefoxitin were detected for presence of plasmid ampC genes and chromosomal ampC promoter region by PCR. All amplified fragments were digested by Mae Ⅲ and 21 were sequenced directly. Results The -35 region mutation was found by Mae Ⅲ digestion in 12 of the 40 isolates. In 21 sequenced isolates, 5 isolates showing -35 region Mae Ⅲ digestion mutation each had a point mutation （T→A at position -32）, 11 isolates had mutations mainly at positions ＋ 22, ＋ 26, ＋ 27, and ＋ 32 in attenuator, and 3 isolates had four different mutations at positions -42, -18, -1 and ＋ 58, and the mutation at -42 changed from C to T, creating a hexamer with perfect homology to the consensus -35 sequence. Conclusion The results suggest that the -42, -32, and stem-loop structures of attenuator mutations play an important role in Escherichia coli resistance to broad spectrum cephalosporins by increasing ampC transcription.
出处
《临床检验杂志》
CAS
CSCD
北大核心
2008年第6期415-418,共4页
Chinese Journal of Clinical Laboratory Science
基金
南京军区医药卫生科研基金课题(07M089)
