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A novel extended-spectrum TEM-type beta-lactamase, TEM-138, from Salmonella enterica serovar Infantis

Chedly Chouchani1, Renaud Berlemont, Afef Masmoudi

  • 1Laboratoire de Biochimie et de Biotechnologie, Faculté des Sciences de Tunis, 2092 El-Manar II, Tunisia.

Antimicrobial Agents and Chemotherapy
|August 31, 2006
PubMed

Insights

A new TEM beta-lactamase, TEM-138, was discovered in Salmonella Infantis, showing extended-spectrum activity against antibiotics like ceftazidime. This enzyme, TEM-138, possesses unique mutations conferring enhanced resistance capabilities.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Antimicrobial Resistance

Background:

  • Beta-lactamase enzymes are a primary mechanism of bacterial resistance to beta-lactam antibiotics.
  • Extended-spectrum beta-lactamases (ESBLs) confer resistance to a wider range of beta-lactam drugs, posing significant clinical challenges.
  • The emergence of novel beta-lactamases necessitates continuous surveillance and characterization to combat antimicrobial resistance.

Purpose of the Study:

  • To identify and characterize a novel TEM beta-lactamase from a clinical isolate.
  • To investigate the specific mutations responsible for the extended-spectrum activity of the novel enzyme.
  • To assess the enzymatic activity of the new beta-lactamase against key antibiotics.

Main Methods:

  • Isolation and identification of the novel beta-lactamase (TEM-138) from a ceftazidime-resistant Salmonella enterica serovar Infantis.
  • Genetic analysis to determine the mutations in TEM-138 compared to TEM-1 (E104K, N175I, G238S).
  • Cloning and expression of the bla(TEM-138) gene in Escherichia coli for functional characterization and enzymatic activity assays.

Main Results:

  • A novel natural TEM beta-lactamase, designated TEM-138, was identified.
  • TEM-138 exhibits extended-spectrum activity, including ceftazidimase and cefotaximase activity.
  • The bla(TEM-138) gene was found on a transferable 50-kb plasmid, indicating potential for horizontal gene transfer.

Conclusions:

  • TEM-138 represents a new variant of TEM beta-lactamase with significant extended-spectrum activity.
  • The identified mutations (E104K, N175I, G238S) are crucial for TEM-138's enhanced enzymatic properties.
  • The presence of bla(TEM-138) on a plasmid highlights the ongoing threat of transferable antibiotic resistance genes in clinical settings.

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