Appearance of aac(6')-Ib-cr gene among extended-spectrum beta-lactamase-producing Enterobacteriaceae in a French hospital

J Infect. 2008 Jun;56(6):454-9. doi: 10.1016/j.jinf.2008.03.010. Epub 2008 Apr 28.


Objectives: The aac(6')-Ib gene encodes many variants of an aminoglycoside-acetyltransferase enzyme that is responsible for amikacin resistance. Recently, a new variant aac(6')-Ib-cr capable of modifying aminoglycosides and fluoroquinolones has been described. The aim of our study was to observe the appearance and the location of the aac(6')-Ib gene in extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae strains.

Methods: Sixty-six and nine non-clonal ESBL-producing Enterobacteriaceae strains were isolated, respectively, for one 3-year period from 1999 to 2001 and one 2-month period in 2005 in a French Hospital (Paris, France).

Results: Among these isolates, 35 of them carried the aac(6')-Ib gene. Fourteen out of the aac(6')-Ib genes of the period 1 and two of the period 2 were genes cassette located within class 1 integrons, whereas 16 and 3, respectively, were outside integrons. One of these encoded an aminoglycoside-acetyltransferase enzyme leading to an acetyltransferase that confers resistance to all aminoglycosides. The new -cr variant of aac(6')-Ib was detected in three Escherichia coli isolates in 2005 always associated with CTX-M-15 enzyme.

Conclusions: The aac(6')-Ib-cr gene, responsible for antibiotic resistance to two very different drugs, is emerging in ESBL-producing Enterobacteriaceae strains isolated in France especially in strains carrying the bla(CTx-M-15) gene.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetyltransferases / genetics*
  • Anti-Bacterial Agents / pharmacology
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Cross Infection / epidemiology
  • Cross Infection / microbiology
  • DNA, Bacterial / chemistry
  • Enterobacteriaceae / drug effects*
  • Enterobacteriaceae / enzymology
  • Enterobacteriaceae / genetics*
  • Enterobacteriaceae Infections / drug therapy
  • Enterobacteriaceae Infections / epidemiology
  • Enterobacteriaceae Infections / microbiology*
  • France / epidemiology
  • Gene Expression Regulation, Bacterial
  • Genes, Bacterial
  • Hospitals
  • Humans
  • Microbial Sensitivity Tests
  • beta-Lactam Resistance / genetics*
  • beta-Lactamases / metabolism*
  • beta-Lactams / pharmacology


  • Anti-Bacterial Agents
  • Bacterial Proteins
  • DNA, Bacterial
  • beta-Lactams
  • Acetyltransferases
  • aminoglycoside acetyltransferase
  • beta-Lactamases