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Transmission of Chromosomal MDR DNA Fragment Encoding Ciprofloxacin Resistance by a Conjugative Helper Plasmid in

Chen Yang1,2, Kaichao Chen3, Edward Wai-Chi Chan4

  • 1College of Animal Science & Technology, Nanjing Agricultural University, Nanjing, China.

Frontiers in Microbiology
|October 19, 2020
PubMed

Insights

Researchers discovered a new 188 kb fusion plasmid in Salmonella Derby. This plasmid, formed by a chromosomal DNA fragment and a conjugative plasmid, enhances the spread of antibiotic resistance genes.

Area of Science:

  • Microbiology
  • Genetics
  • Molecular Biology

Background:

  • Increasing resistance to ciprofloxacin, a key Salmonella treatment, is a growing public health concern.
  • Salmonella Derby strains frequently exhibit resistance due to chromosome-encoded plasmid-mediated quinolone resistance (PMQR) genes.

Purpose of the Study:

  • To investigate the mechanism of antibiotic resistance development and transfer in Salmonella Derby.
  • To identify and characterize novel mobile genetic elements contributing to multidrug resistance (MDR).

Main Methods:

  • Isolation and characterization of a conjugative plasmid (pSa64-96kb) from a Salmonella Derby isolate (Sa64).
  • Identification of a chromosomal MDR DNA fragment containing PMQR genes (aac(6')-Ib-cr and qnrS2).
  • Analysis of IS26 element-mediated excision, fusion, and transfer of the MDR fragment to form a novel 188 kb plasmid.

Main Results:

  • A new 188 kb fusion plasmid was formed through the integration of a chromosomal MDR fragment into pSa64-96kb.
  • The IS26 element facilitated the excision and homologous recombination of the MDR fragment, enabling plasmid fusion.
  • The resulting fusion plasmid was successfully transferred to Escherichia coli J53, demonstrating its transmissibility.

Conclusions:

  • Dynamic interactions between chromosomal fragments and plasmids significantly drive antibiotic resistance.
  • The IS26 element plays a crucial role in enhancing the development and transferability of mobile resistance genes.
  • Understanding these mechanisms is vital for combating the spread of antibiotic resistance in bacterial pathogens.
Keywords:
PMQR genesSalmonellachromosomal fragmentciprofloxacin resistanceconjugative helper plasmid

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