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Characterizing Multidrug Efflux Systems in Acinetobacter baumannii Using an Efflux-Deficient Bacterial Strain and a Single-Copy Gene Expression System
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A module located at a chromosomal integration hot spot is responsible for the multidrug resistance of a reference

Mathilde Lescat1, Alexandra Calteau, Claire Hoede

  • 1INSERM U722 and Université Paris 7 Denis Diderot, Site Xavier Bichat, 16 rue Henri Huchard, 75018 Paris, France.

Antimicrobial Agents and Chemotherapy
|April 15, 2009
PubMed

Insights

Escherichia coli clonal group A (CGA) strains often show multidrug resistance. Whole-genome sequencing identified a specific genomic region, the GRM, responsible for this resistance in CGA E. coli.

Area of Science:

  • Microbiology
  • Genomics
  • Antimicrobial Resistance

Background:

  • Escherichia coli clonal group A (CGA) is frequently associated with multidrug resistance, including resistance to ampicillin, chloramphenicol, streptomycin, sulfonamides, tetracycline, and trimethoprim (ACSSuTTp).
  • This resistance pattern contributes significantly to trimethoprim-sulfamethoxazole-resistant E. coli urinary tract infections.

Purpose of the Study:

  • To elucidate the genetic basis of the ACSSuTTp multidrug resistance phenotype in the reference CGA strain UMN026.
  • To characterize the genomic region responsible for antimicrobial resistance in CGA E. coli.

Main Methods:

  • Whole-genome sequencing and annotation of the UMN026 E. coli strain.
  • Comparative genomic analysis of the leuX tRNA genomic island across 14 sequenced E. coli genomes.

Main Results:

  • A unique 23-kbp chromosomal region, termed the genomic resistance module (GRM), was identified within a 105-kbp genomic island at the leuX tRNA.
  • The GRM contains genes conferring the ACSSuTTp resistance phenotype and shows evidence of multiple horizontal gene transfers.
  • The leuX tRNA genomic island is a hot spot for integration, with variable subregions not correlating with phylogenetic group or pathotype.

Conclusions:

  • Whole-genome sequencing is crucial for identifying genetic elements driving antimicrobial resistance.
  • This study provides the first evidence of bla(TEM) and dhfrVII genes located on the chromosome in E. coli strains.

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