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Quantification of Plasmid-Mediated Antibiotic Resistance in an Experimental Evolution Approach
12:32

Quantification of Plasmid-Mediated Antibiotic Resistance in an Experimental Evolution Approach

Published on: December 14, 2019

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A large self-transmissible resistance plasmid from Nigeria contains genes that ameliorate a carrying cost

Rubén Monárrez1, Molly Braun1, Olivia Coburn-Flynn1

  • 1Department of Biology, Haverford College, Pennsylvania, USA.

Scientific Reports
|December 25, 2019
PubMed

Insights

Mobile genetic elements drive antimicrobial resistance. A large plasmid, pMB2, carrying multiple resistance genes, enhances bacterial fitness and transmissibility, exacerbating the spread of antimicrobial resistance.

Area of Science:

  • Microbiology
  • Genetics
  • Molecular Biology

Background:

  • Antimicrobial resistance (AMR) is a growing global health threat, largely driven by mobile genetic elements like plasmids.
  • Fluoroquinolone resistance in Escherichia coli is a significant concern, particularly in regions like Nigeria.

Purpose of the Study:

  • To screen fluoroquinolone-resistant E. coli isolates from Nigeria for plasmid-mediated quinolone resistance (PMQR) genes.
  • To characterize a self-transmissible plasmid (pMB2) identified in a resistant E. coli strain, focusing on its genetic content and impact on bacterial fitness.

Main Methods:

  • Screening of 94 E. coli isolates for six PMQR genes.
  • Plasmid mapping, sequencing, and characterization of pMB2 (125 Kb).
  • Growth rate and fitness assays comparing wild-type and mini-plasmid strains, including trans-complementation studies.

Main Results:

  • Four out of 16 isolates positive for PMQR genes carried the aac-6-Ib-cr gene.
  • The IncFII plasmid pMB2 harbored aac-6-Ib-cr, blaCTX-M-15, seven other resistance genes, and multiple pseudogenes.
  • pMB2 conferred a growth advantage in both rich and minimal media; a 32 Kb fragment deletion reduced this advantage, with sitABCD genes identified as crucial for iron-depleted media growth.

Conclusions:

  • Large, self-transmissible plasmids like pMB2, possessing multiple resistance genes and ancillary functions, contribute significantly to bacterial fitness and AMR spread.
  • The findings highlight how plasmid-borne traits beyond antimicrobial resistance can drive plasmid retention and transmissibility, complicating AMR containment efforts.

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