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Characterization of blaCTX-M-14 transposition from plasmid to chromosome in Escherichia coli experimental strain

Kouta Hamamoto1, Toshiro Tokunaga2, Nobuyoshi Yagi2

  • 1Laboratory of Microbiology, School of Health Sciences, Faculty of Medicine, University of the Ryukyus, Okinawa 903-0215, Japan; Research Fellow of the Japan Society for the Promotion of Science, Tokyo 102-0083, Japan.

International Journal of Medical Microbiology : IJMM
|January 22, 2020
PubMed

Insights

The insertion sequence ISEcp1 facilitates the transfer of blaCTX-M-14 genes from plasmids to bacterial chromosomes. This molecular mechanism explains the increased prevalence of extended-spectrum beta-lactamase producing E. coli in clinical and community settings.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Genetics

Background:

  • The blaCTX-M gene, often found on plasmids, is a key determinant of extended-spectrum beta-lactamase (ESBL) production in bacteria.
  • The insertion sequence ISEcp1 is frequently associated with blaCTX-M genes, mediating their transposition.
  • Recent studies indicate an increasing prevalence of chromosomally located blaCTX-M genes in ESBL-producing bacterial isolates.

Purpose of the Study:

  • To investigate the frequency and molecular mechanisms of ISEcp1-mediated transposition of the blaCTX-M-14 gene from plasmids to the chromosome.
  • To identify and characterize the chromosomal integration sites of blaCTX-M-14 in Escherichia coli.

Main Methods:

  • Utilized an experimental strain of Escherichia coli for controlled observation of plasmid-to-chromosome transposition.
  • Employed five independent screening procedures to identify blaCTX-M-14 transposition sites.
  • Characterized the DNA sequences flanking the integrated blaCTX-M-14 genes, including direct repeats (DRs) and inverted repeat sequences.

Main Results:

  • Identified 102 distinct chromosomal transposition sites for blaCTX-M-14 in 126 E. coli isolates.
  • Observed 5-bp direct repeat sequences and identical left terminal inverted sequences in 80 isolates, suggesting ISEcp1-mediated integration.
  • Found high diversity in the 5'-flanking sequences of right terminal DRs and no consensus right terminal inverted repeat sequences.
  • Determined the frequency of ISEcp1-mediated blaCTX-M-14 transposition from plasmid to chromosome in the experimental strain to be 0.51% (SD = 0.37).

Conclusions:

  • The molecular characteristics of ISEcp1 contribute to the efficient transposition of blaCTX-M-14 to chromosomal locations.
  • This mechanism provides a plausible explanation for the high detection rates of E. coli with chromosomally located blaCTX-M-14 in clinical and community environments.
  • Understanding these transposition events is crucial for monitoring and controlling the spread of antibiotic resistance.
Keywords:
ESBLEscherichia coliTransfer frequencybla(CTX-M)

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