title: Investigation of a multiresistance gene cfr that fails to mediate resistance to phenicols and oxazolidinones in Enterococcus faecalis.
abstract: OBJECTIVE
  To investigate the basis of susceptibility to phenicols and oxazolidinones of the porcine Enterococcus faecalis CPPF5 despite the presence of the multiresistance gene cfr.
  
  
  METHODS
  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 RT-PCR and western blotting, respectively, and modifications at A2503 within the 23S rRNA sequence were identified by primer extension.
  
  
  RESULTS
  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 12,270 bp sequence of the smaller plasmid, pCPPF5, was determined and shared 99.9% (12,269/12,270 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Beijing Key Laboratory of Detection Technology for Animal-Derived Food Safety, College of Veterinary Medicine, China Agricultural University, Beijing 100193, P. R. China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.forename: Yang
authors.initials: Y
authors.lastname: Wang
authors.forename: Stefan
authors.initials: S
authors.lastname: Schwarz
authors.forename: Shaolin
authors.initials: S
authors.lastname: Wang
authors.forename: Leran
authors.initials: L
authors.lastname: Chen
authors.forename: Congming
authors.initials: C
authors.lastname: Wu
authors.forename: Jianzhong
authors.initials: J
authors.lastname: Shen
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics*; D015139:Blotting, Southern; D002417:Cattle; D002701:Chloramphenicol / Q000494:pharmacology*; D003227:Conjugation, Genetic; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D024881:Drug Resistance, Bacterial; D024901:Drug Resistance, Multiple, Bacterial; D013293:Enterococcus faecalis / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D020869:Gene Expression Profiling; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D023303:Oxazolidinones / Q000494:pharmacology*; D010957:Plasmids / Q000032:analysis; D012338:RNA, Ribosomal, 23S / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D013839:Thiamphenicol / Q000031:analogs & derivatives / Q000494:pharmacology; D014158:Transcription, Genetic
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D023303:Oxazolidinones; D012338:RNA, Ribosomal, 23S; D002701:Chloramphenicol; C035534:florfenicol; D013839:Thiamphenicol
keywords: RNA methylation; linezolid; pigs; transcription; translation