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Two different erm(C)-carrying plasmids in the same methicillin-resistant Staphylococcus aureus CC398 isolate from a

Sarah Wendlandt1, Kristina Kadlec1, Andrea T Feßler1

  • 1Institute of Farm Animal Genetics, Friedrich-Loeffler-Institut (FLI), Neustadt-Mariensee, Germany.

Veterinary Microbiology
|February 21, 2014
PubMed

Insights

A rare methicillin-resistant Staphylococcus aureus (MRSA) isolate from broiler farms carried two small plasmids with the same macrolide resistance gene, erm(C). Different replication genes allowed stable coexistence, offering insights into antimicrobial resistance.

Area of Science:

  • Veterinary Microbiology
  • Molecular Biology
  • Antimicrobial Resistance

Background:

  • Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant threat in livestock, necessitating studies on its antimicrobial resistance mechanisms.
  • Plasmid-borne resistance genes are crucial for the dissemination of antimicrobial resistance in bacterial populations, including MRSA.

Purpose of the Study:

  • To characterize the plasmid content and antimicrobial resistance genes of a unique MRSA isolate from broiler farms.
  • To investigate the genetic basis for the stable coexistence of multiple plasmids carrying the same resistance gene within a single MRSA cell.

Main Methods:

  • MRSA isolate identification and characterization (CC398, spa type t3015, dru type dt11a).
  • Plasmid profiling and DNA sequencing to identify plasmid-borne genes.
  • Sequence analysis of translational attenuators to understand gene expression.

Main Results:

  • An MRSA isolate harbored one large plasmid with tetracycline, trimethoprim, and kanamycin/neomycin resistance genes, and two small plasmids each carrying an erm(C) gene for macrolide/lincosamide resistance.
  • The two small plasmids, pSWS371 and pSWS372, differed in replication (repL vs. repF) and mobilization genes, with pSWS372 containing additional genes for copy number control and mobilization.
  • Deletions in the translational attenuators of the erm(C) genes on both small plasmids resulted in constitutive gene expression.

Conclusions:

  • The simultaneous presence of two distinct, yet co-resident, small plasmids carrying the same resistance gene (erm(C)) in an MRSA isolate is a rare finding.
  • Different incompatibility groups, indicated by distinct replication genes, explain the stable coexistence of these plasmids.
  • Understanding such plasmid dynamics is vital for tracking and controlling the spread of antimicrobial resistance in livestock-associated MRSA.
Keywords:
Horizontal gene transferLincosamideMRSAMacrolidePlasmid incompatibilityResistance

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