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Novel plasmid-borne gene qacJ mediates resistance to quaternary ammonium compounds in equine Staphylococcus aureus,

Jostein Bjorland1, Terje Steinum, Marianne Sunde

  • 1Department of Reproduction and Forensic Medicine, The Norwegian School of Veterinary Science, Oslo, Norway. jostein.bjorland@veths.no

Antimicrobial Agents and Chemotherapy
|September 25, 2003
PubMed

Insights

Researchers discovered a new gene, qacJ, conferring resistance to quaternary ammonium compounds (QACs) in horse-associated staphylococci. This finding highlights potential risks of antiseptic use in animal infections.

Area of Science:

  • Microbiology
  • Genetics
  • Veterinary Medicine

Background:

  • Quaternary ammonium compounds (QACs) are widely used disinfectants and antiseptics.
  • Antimicrobial resistance is a growing concern in both human and animal health.
  • Staphylococcal species are common causes of chronic infections in horses.

Purpose of the Study:

  • To identify novel genes responsible for QAC resistance in staphylococci from equine infections.
  • To characterize the genetic element carrying the resistance gene.
  • To investigate the molecular epidemiology and potential transfer of the resistance gene.

Main Methods:

  • Identification and sequencing of a novel plasmid-borne gene, qacJ.
  • Characterization of the plasmid pNVH01.
  • Expression of the QacJ protein in a recombinant system and determination of minimum inhibitory concentrations (MICs).
  • Molecular epidemiological analysis using pulsed-field gel electrophoresis (PFGE).

Main Results:

  • A novel plasmid-borne gene, qacJ, conferring resistance to QACs was identified in staphylococci from four horses.
  • The qacJ gene was located on a novel pC194-family plasmid, pNVH01.
  • The QacJ protein showed similarity to known small multidrug resistance proteins but conferred higher benzalkonium chloride resistance.
  • Molecular epidemiology suggested both clonal spread of a qacJ-harboring S. aureus strain and horizontal transfer of the plasmid between staphylococcal species.
  • Identical plasmid sequences in different species indicated recent transfer.

Conclusions:

  • A novel QAC resistance gene, qacJ, has been identified in staphylococci from equine infections.
  • The plasmid pNVH01 carrying qacJ appears to be transferable between staphylococcal species.
  • Extensive use of QAC-containing skin preparations may have selected for staphylococci harboring this novel resistance gene.
  • This discovery has implications for understanding and managing antimicrobial resistance in veterinary settings.

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