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GES-2, a class A beta-lactamase from Pseudomonas aeruginosa with increased hydrolysis of imipenem

L Poirel1, G F Weldhagen, T Naas

  • 1Service de Bactériologie-Virologie, Hôpital de Bicêtre, Assistance Publique/Hôpitaux de Paris, Faculté de Médecine Paris-Sud, 94275 Le Kremlin-Bicêtre, France.

Antimicrobial Agents and Chemotherapy
|August 15, 2001
PubMed

Insights

A novel beta-lactamase, GES-2, was identified in Pseudomonas aeruginosa GW-1, conferring resistance to expanded-spectrum cephalosporins and imipenem. This enzyme

Area of Science:

  • Microbiology
  • Molecular Biology
  • Biochemistry

Background:

  • Pseudomonas aeruginosa is a significant nosocomial pathogen.
  • Antibiotic resistance, particularly to beta-lactams, is a growing global health concern.
  • The emergence of extended-spectrum beta-lactamases (ESBLs) contributes to treatment challenges.

Purpose of the Study:

  • To characterize a novel beta-lactamase, bla(GES-2), identified in a clinical isolate of Pseudomonas aeruginosa.
  • To investigate the substrate profile and inhibitory characteristics of the GES-2 enzyme.
  • To understand the molecular basis for the extended substrate profile of GES-2 compared to GES-1.

Main Methods:

  • Isolation and identification of Pseudomonas aeruginosa GW-1 from a clinical blood culture.
  • Cloning and expression of the beta-lactamase gene bla(GES-2) in Escherichia coli.
  • Biochemical characterization of the purified GES-2 enzyme, including substrate hydrolysis and inhibition assays.
  • Amino acid sequencing of GES-2 and comparison with related beta-lactamases.

Main Results:

  • The bla(GES-2) gene was cloned and expressed, producing a beta-lactamase (GES-2) with a pI of 5.8.
  • GES-2 hydrolyzed expanded-spectrum cephalosporins and demonstrated activity against imipenem.
  • GES-2 exhibited reduced inhibition by clavulanic acid, tazobactam, and imipenem compared to GES-1.
  • A single amino acid substitution (Gly170Asn) in the omega loop of GES-2, compared to GES-1, was identified.

Conclusions:

  • The plasmid-encoded beta-lactamase GES-2 confers resistance to expanded-spectrum cephalosporins and imipenem in Pseudomonas aeruginosa.
  • The Gly170Asn substitution in GES-2 is likely responsible for its extended substrate profile and altered inhibition characteristics.
  • This finding highlights the continuous evolution of beta-lactamases and the need for ongoing surveillance of antibiotic resistance mechanisms.

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