Detection of a New cfr-Like Gene, cfr(B), in Enterococcus faecium Isolates Recovered from Human Specimens in the United States as Part of the SENTRY Antimicrobial Surveillance Program

Antimicrob Agents Chemother. 2015 Oct;59(10):6256-61. doi: 10.1128/AAC.01473-15. Epub 2015 Jul 27.


Two linezolid-resistant Enterococcus faecium isolates (MICs, 8 μg/ml) from unique patients of a medical center in New Orleans were included in this study. Isolates were initially investigated for the presence of mutations in the V domain of 23S rRNA genes and L3, L4, and L22 ribosomal proteins, as well as cfr. Isolates were subjected to pulsed-field gel electrophoresis (just one band difference), and one representative strain was submitted to whole-genome sequencing. Gene location was also determined by hybridization, and cfr genes were cloned and expressed in a Staphylococcus aureus background. The two isolates had one out of six 23S rRNA alleles mutated (G2576T), had wild-type L3, L4, and L22 sequences, and were positive for a cfr-like gene. The sequence of the protein encoded by the cfr-like gene was most similar (99.7%) to that found in Peptoclostridium difficile, which shared only 74.9% amino acid identity with the proteins encoded by genes previously identified in staphylococci and non-faecium enterococci and was, therefore, denominated Cfr(B). When expressed in S. aureus, the protein conferred a resistance profile similar to that of Cfr. Two copies of cfr(B) were chromosomally located and embedded in a Tn6218 similar to the cfr-carrying transposon described in P. difficile. This study reports the first detection of cfr genes in E. faecium clinical isolates in the United States and characterization of a new cfr variant, cfr(B). cfr(B) has been observed in mobile genetic elements in E. faecium and P. difficile, suggesting potential for dissemination. However, further analysis is necessary to access the resistance levels conferred by cfr(B) when expressed in enterococci.

Publication types

  • Case Reports

MeSH terms

  • Alleles
  • Anti-Bacterial Agents / pharmacology
  • Bacterial Proteins / genetics*
  • Bacterial Proteins / metabolism
  • Chromosomes, Bacterial / chemistry*
  • Cloning, Molecular
  • DNA Transposable Elements
  • Drug Resistance, Multiple, Bacterial / genetics*
  • Enterococcus faecium / classification
  • Enterococcus faecium / drug effects
  • Enterococcus faecium / genetics*
  • Enterococcus faecium / isolation & purification
  • Epidemiological Monitoring
  • Gene Dosage
  • Gene Expression
  • Gram-Positive Bacterial Infections / drug therapy
  • Gram-Positive Bacterial Infections / microbiology
  • Humans
  • Male
  • Middle Aged
  • Oxazolidinones / pharmacology
  • Phylogeny
  • RNA, Ribosomal, 23S / genetics*
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Ribosomal Proteins / genetics*
  • Ribosomal Proteins / metabolism
  • Staphylococcus aureus / genetics
  • Staphylococcus aureus / metabolism
  • United States
  • beta-Lactams / pharmacology


  • Anti-Bacterial Agents
  • Bacterial Proteins
  • DNA Transposable Elements
  • Oxazolidinones
  • RNA, Ribosomal, 23S
  • Recombinant Proteins
  • Ribosomal Proteins
  • beta-Lactams