Nakano Ryuichi, Okamoto Ryoichi, Nakano Yumiko, Kaneko Kenichi, Okitsu Naohiro, Hosaka Yoshio, Inoue Matsuhisa
Department of Microbiology, School of Medicine and Environmental Infectious Disease, Graduate School of Medical Sciences, Kitasato University, Sagamihara, Kanagawa, Japan.
Antimicrob Agents Chemother. 2004 Apr;48(4):1151-8. doi: 10.1128/AAC.48.4.1151-1158.2004.
A clinical isolate of Escherichia coli from a patient in Japan, isolate KU6400, was found to produce a plasmid-encoded beta-lactamase that conferred resistance to extended-spectrum cephalosporins and cephamycins. Resistance arising from production of a beta-lactamase could be transferred by either conjugation or transformation with plasmid pKU601 into E. coli ML4947. The substrate and inhibition profiles of this enzyme resembled those of the AmpC beta-lactamase. The resistance gene of pKU601, which was cloned and expressed in E. coli, proved to contain an open reading frame showing 99.8% DNA sequence identity with the ampC gene of Citrobacter freundii GC3. DNA sequence analysis also identified a gene upstream of ampC whose sequence was 99.0% identical to the ampR gene from C. freundii GC3. In addition, a fumarate operon (frdABCD) and an outer membrane lipoprotein (blc) surrounding the ampR-ampC genes in C. freundii were identified, and insertion sequence (IS26) elements were observed on both sides of the sequences identified (forming an IS26 composite transposon); these results confirm the evidence of the translocation of a beta-lactamase-associated gene region from the chromosome to a plasmid. Finally, we describe a novel plasmid-encoded AmpC beta-lactamase, CFE-1, with an ampR gene derived from C. freundii.
从一名日本患者身上分离出的大肠杆菌临床菌株KU6400，被发现可产生一种质粒编码的β-内酰胺酶，该酶赋予了对超广谱头孢菌素和头霉素的抗性。由β-内酰胺酶产生的抗性可通过接合或用质粒pKU601转化转移至大肠杆菌ML4947。这种酶的底物和抑制谱与AmpCβ-内酰胺酶相似。在大肠杆菌中克隆并表达的pKU601抗性基因，经证实含有一个开放阅读框，其与弗氏柠檬酸杆菌GC3的ampC基因的DNA序列一致性达99.8%。DNA序列分析还鉴定出ampC上游的一个基因，其序列与弗氏柠檬酸杆菌GC3的ampR基因的一致性为99.0%。此外，还鉴定出了弗氏柠檬酸杆菌中围绕ampR - ampC基因的一个延胡索酸操纵子（frdABCD）和一个外膜脂蛋白（blc），并且在鉴定出的序列两侧观察到插入序列（IS26）元件（形成一个IS26复合转座子）；这些结果证实了β-内酰胺酶相关基因区域从染色体易位至质粒的证据。最后，我们描述了一种新型的质粒编码AmpCβ-内酰胺酶CFE-1，其具有源自弗氏柠檬酸杆菌的ampR基因。
