Investigation of a multiresistance gene cfr that fails to mediate resistance to phenicols and oxazolidinones in Enterococcus faecalis
Investigation of a multiresistance gene cfr that fails to mediate resistance to phenicols and oxazolidinones in Enterococcus faecalis
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DOI：
10.1093/jac/dkt459
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发表时间：
2014-04-01
影响因子：
5.2
通讯作者：
Shen, Jianzhong
中科院分区：
文献类型：
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作者：
Liu, Yang;Wang, Yang;Shen, Jianzhong
为探讨粪肠球菌CPPF 5对酚类和恶唑烷酮类药物敏感性的基础，采用Southern杂交、接合和转化分析等方法，对粪肠球菌CPPF 5中cfr基因的质粒定位和转移性进行了研究。通过序列分析确定cfr的遗传环境。通过RTPCR和Western blotting检测cfr的转录和翻译，并通过引物延伸鉴定2 - 3S rRNA序列中A2503处的修饰，电转化和Southern blotting检测表明CPPF 5和CPPF 5 B2 -3含有两个大小为50和12 kb的携带cfr的质粒。结果表明，小质粒pCPPF 5的全序列为12270 bp，与大肠杆菌中携带cfr的质粒pEF-01的相应序列同源性为99.9（12269/12270 bp）。来源于牛的粪便。测序结果表明，50 kb质粒中cfr的遗传环境与pCPPF 5相同。虽然检测到cfr mRNA、Cfr蛋白和A2503位点的修饰，但携带cfr的E15 B2 -3对氯霉素、氟苯尼考和利奈唑胺的MIC没有升高，表明cfr不能介导大肠杆菌对相应抗生素的耐药性。这是首次报道cfr基因不能提高相应抗生素的MIC。虽然表观无耐药表型的遗传基础仍有待确定，但这一发现可能对靶向cfr基因的监测研究有意义。
To investigate the basis of susceptibility to phenicols and oxazolidinones of the porcine Enterococcus faecalis CPPF5 despite the presence of the multiresistance gene cfr.Southern blotting, conjugation and transformation analyses were conducted to confirm the plasmid location and transferability of cfr in CPPF5. The genetic environment of cfr was determined by sequence analysis. Transcription and translation of cfr were examined by RTPCR and western blotting, respectively, and modifications at A2503 within the 23S rRNA sequence were identified by primer extension.Electrotransformation and Southern blotting indicated that CPPF5 and its transformant 5B2-3 contained two cfr-carrying plasmids 50 and 12 kb in size. The complete 12270 bp sequence of the smaller plasmid, pCPPF5, was determined and shared 99.9 (12269/12270 bp) identity with the corresponding region of the cfr-carrying plasmid pEF-01 in E. faecalis of cattle origin. Moreover, the genetic environment of cfr in the 50 kb plasmid was the same as that in pCPPF5 according to sequencing results. Although cfr mRNA, Cfr protein and a modification at the A2503 site were detected, the cfr-carrying transformant 5B2-3 did not have elevated MICs of chloramphenicol, florfenicol and linezolid, indicating that cfr fails to mediate resistance to the respective antibiotics in E. faecalis.This is the first report of the cfr gene failing to elevate MICs of the corresponding antibiotics. Although the genetic basis for the apparent no resistance phenotype remains to be determined, this finding may have implications for surveillance studies that target the cfr gene.