Novel plasmid-encoded ceftazidime-hydrolyzing CTX-M-53 extended-spectrum beta-lactamase from Salmonella enterica

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Testing the Role of Multicopy Plasmids in the Evolution of Antibiotic Resistance
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Testing the Role of Multicopy Plasmids in the Evolution of Antibiotic Resistance

Published on: May 2, 2018

Benoît Doublet1, Sophie A Granier, Frédéric Robin

  • 1Centre National de Référence des Salmonella, Laboratoire des Bactéries Pathogènes Entériques, Institut Pasteur, 28 rue du Docteur Roux, 75724 Paris Cedex 15, France.

Antimicrobial Agents and Chemotherapy
|March 11, 2009
PubMed

Insights

A novel CTX-M-53 beta-lactamase was identified in Salmonella enterica from French cockles. This extended-spectrum beta-lactamase (ESBL) confers resistance to cephalosporins, contributing to antimicrobial resistance concerns.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Genetics

Background:

  • Extended-spectrum cephalosporins are crucial antibiotics.
  • The emergence of beta-lactamases, such as CTX-M enzymes, poses a significant threat to their efficacy.
  • Salmonella enterica is an important foodborne pathogen.

Purpose of the Study:

  • To characterize a novel CTX-M beta-lactamase identified in Salmonella enterica isolates.
  • To investigate the genetic basis and epidemiological significance of this new enzyme.

Main Methods:

  • Isolation and identification of Salmonella enterica.
  • Antimicrobial susceptibility testing, including resistance to cefotaxime and ceftazidime.
  • Molecular characterization of the beta-lactamase gene (blaCTX-M-53) and its plasmid location.
  • Plasmid sequencing and analysis of insertion sequences.
  • Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) for genetic relatedness.

Main Results:

  • Four Salmonella enterica isolates resistant to extended-spectrum cephalosporins were identified in French cockles.
  • A novel extended-spectrum beta-lactamase, CTX-M-53, belonging to the CTX-M-1 group, was characterized.
  • CTX-M-53 possesses the Asp240Gly substitution, enhancing ceftazidime hydrolysis.
  • The blaCTX-M-53 gene was located on an 11-kb mobilizable plasmid (pWES-1) associated with insertion sequences IS26 and ISSen2.
  • Isolates were genetically indistinguishable by PFGE, and shared MLST sequence type ST14, despite serotype differences.
  • The plasmid mobilization module showed similarity to quinolone resistance plasmids.

Conclusions:

  • This study reports the first characterization of the CTX-M-53 ESBL, an enzyme conferring resistance to ceftazidime.
  • The presence of CTX-M-53 in Salmonella enterica highlights the potential for foodborne transmission of antimicrobial resistance genes.
  • The genetic environment of the blaCTX-M-53 gene on a mobilizable plasmid suggests potential for further dissemination.

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