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Biochemical properties of inducible beta-lactamases produced from Xanthomonas maltophilia

R Paton1, R S Miles, S G Amyes

  • 1Department of Medical Microbiology, Medical School, University of Edinburgh, United Kingdom.

Antimicrobial Agents and Chemotherapy
|September 1, 1994
PubMed

Insights

Xanthomonas maltophilia produces multiple beta-lactamases, including a metallo-beta-lactamase and others with broad-spectrum activity. These enzymes exhibit varied resistance to inhibitors and hydrolysis profiles, expanding known resistance mechanisms.

Area of Science:

  • Microbiology
  • Biochemistry
  • Enzymology

Background:

  • Xanthomonas maltophilia is an opportunistic pathogen.
  • Beta-lactamase production is a key mechanism of antibiotic resistance in bacteria.
  • Previous studies identified L1 and L2 beta-lactamases in X. maltophilia.

Purpose of the Study:

  • To characterize the beta-lactamases produced by X. maltophilia strains.
  • To investigate the enzymatic properties and inhibitor profiles of these beta-lactamases.

Main Methods:

  • Isolation and characterization of beta-lactamases from X. maltophilia blood culture isolates.
  • Isoelectric focusing (IEF) to determine isoelectric points (pI).
  • Gel filtration and SDS-PAGE for molecular size determination.
  • Enzyme activity assays against various beta-lactam antibiotics.
  • Inhibition studies with specific inhibitors (e.g., EDTA, clavulanate).

Main Results:

  • Four distinct beta-lactamases were identified.
  • A metallo-beta-lactamase (pI 6.8) showed penicillinase activity, hydrolyzed most beta-lactams except aztreonam, and was inhibited by heavy metals and EDTA.
  • Other beta-lactamases (pI 5.2-6.6) had broad-spectrum activity against most beta-lactams (except imipenem, aztreonam) and were inhibited by clavulanate and BRL 42715.
  • Molecular weight discrepancies between gel filtration and SDS-PAGE suggested oligomeric structures.

Conclusions:

  • X. maltophilia produces a diverse array of beta-lactamases beyond the previously identified L1 and L2.
  • The characterized enzymes possess distinct biochemical properties and resistance profiles, contributing to the pathogen's antibiotic resistance.
  • Understanding these enzymes is crucial for developing effective therapeutic strategies against X. maltophilia infections.

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