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Molecular structure and transferability of Tn1546-like elements in Enterococcus faecium isolates from clinical,

M Talebi1, M R Pourshafie, M Katouli

  • 1Department of Microbiology, Pasteur Institute of Iran, Tehran, Iran.

Applied and Environmental Microbiology
|January 15, 2008
PubMed

Insights

The vancomycin resistance gene Tn1546 was studied in Enterococcus faecium isolates from Iran. Lineage 3 of Tn1546 showed widespread dissemination across clinical and environmental samples.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Environmental Science

Background:

  • Vancomycin-resistant Enterococcus faecium (VREF) poses a significant public health threat.
  • The Tn1546 transposon is a key element mediating vancomycin resistance in Enterococcus faecium.
  • Understanding the molecular epidemiology and transferability of Tn1546 is crucial for controlling VREF spread.

Purpose of the Study:

  • To investigate the molecular structure and transferability of the Tn1546 transposon.
  • To characterize Tn1546 in vanA VREF isolates from clinical, surface water, and sewage sources in Tehran, Iran.
  • To determine the genomic organization and dissemination patterns of Tn1546.

Main Methods:

  • Molecular characterization using restriction fragment length polymorphism (RFLP) and DNA sequencing.
  • Long-PCR amplification to determine Tn1546 molecular size.
  • Filter-mating conjugation assays to assess horizontal transferability.
  • Pulsed-field gel electrophoresis (PFGE) for genetic diversity analysis.

Main Results:

  • Tn1546 elements varied in size from 10.8 to 12.8 kb.
  • A deletion/mutation upstream from nucleotide 170 was found in 31.5% of isolates.
  • Horizontal transferability varied, with rates of 10(-5) to 10(-6) per donor for some isolates.
  • Three distinct genomic organizations of Tn1546 were identified, with lineage 3 being the most prevalent (72.1%).
  • A single Enterococcus faecium clone (designated 44) was common across clinical and sewage samples.
  • Lineage 3 Tn1546 was highly disseminated among isolates with diverse PFGE patterns.

Conclusions:

  • Tn1546 exhibits significant molecular diversity and varying transferability in Iranian VREF isolates.
  • The prevalence of lineage 3 suggests its successful adaptation and dissemination in both clinical and environmental settings.
  • The identification of a common clone across different sources highlights potential transmission routes of VREF.

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