High-level ciprofloxacin resistance among hospital-adapted Enterococcus faecium (CC17)

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Isolation and Identification of Waterborne Antibiotic-Resistant Bacteria and Molecular Characterization of their Antibiotic Resistance Genes
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Guido Werner1, Carola Fleige, Birgit Ewert

  • 1Robert Koch Institute, Wernigerode Branch, Wernigerode, Germany. wernerg@rki.de

International Journal of Antimicrobial Agents
|December 17, 2009
PubMed

Insights

Hospital-adapted Enterococcus faecium strains, particularly CC17, frequently exhibit high-level ciprofloxacin resistance. This acquired resistance is widespread among hospital isolates and linked to specific gyrA and parC mutations.

Area of Science:

  • Microbiology
  • Genomics
  • Infectious Diseases

Background:

  • Hospital-adapted Enterococcus faecium possess distinct genomic content compared to colonizing strains.
  • Multilocus sequence typing (MLST) identifies hospital-adapted strains within clonal complexes (CCs), notably CC17.
  • Acquired ampicillin resistance is common in European hospital E. faecium, with recent reports suggesting high-level ciprofloxacin resistance.

Purpose of the Study:

  • To investigate the prevalence and genetic basis of high-level ciprofloxacin resistance in hospital-adapted Enterococcus faecium.
  • To determine the association between ciprofloxacin resistance and specific MLST types and mutations.

Main Methods:

  • Retrospective analysis of 609 clinical Enterococcus faecium isolates from German hospitals (1997-2007).
  • Determination of ciprofloxacin minimum inhibitory concentrations (MICs) and establishment of a high-level resistance breakpoint (>16mg/L).
  • Genomic analysis of 98 resistant isolates, including MLST, pulsed-field gel electrophoresis (PFGE), and sequencing of gyrA and parC genes.

Main Results:

  • High-level ciprofloxacin resistance was identified in isolates belonging to 26 different MLST types, all within CC17, indicating broad prevalence.
  • The resistance was strongly associated with mutations in the gyrA and parC genes, with eleven distinct allele types or combinations identified.
  • Analysis of MLST and PFGE types revealed variations in the emergence and dissemination patterns of resistant strains and their associated mutations.

Conclusions:

  • High-level ciprofloxacin resistance is a prevalent acquired trait among hospital-adapted Enterococcus faecium (CC17) in German hospitals.
  • The resistance is primarily mediated by mutations in gyrA and parC, with diverse genetic backgrounds and spread dynamics observed.
  • Understanding the molecular epidemiology of ciprofloxacin resistance is crucial for managing hospital-acquired infections caused by E. faecium.

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