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Class D β-lactamases: are they all carbapenemases?
Nuno T Antunes1, Toni L Lamoureaux, Marta Toth
1Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, USA.
Antimicrobial Agents and Chemotherapy
|January 29, 2014
Summary
Carbapenem-hydrolyzing class D β-lactamases (CHDLs) like OXA-2 and OXA-10 exhibit carbapenem resistance in Acinetobacter baumannii, challenging their narrow-spectrum classification. These findings suggest other enzymes may also be CHDLs.
Area of Science:
- Microbiology
- Biochemistry
- Molecular Biology
Background:
- Carbapenem-hydrolyzing class D β-lactamases (CHDLs) are critical for carbapenem resistance in life-threatening infections.
- Acinetobacter baumannii is a primary host for many CHDLs.
- OXA-2 and OXA-10, typically found in Pseudomonas aeruginosa, are classified as narrow-spectrum enzymes.
Purpose of the Study:
- To investigate the spectrum of activity and carbapenem-hydrolyzing capabilities of OXA-2 and OXA-10 enzymes.
- To re-evaluate the classification of OXA-2 and OXA-10 based on their activity in different bacterial hosts.
- To explore the potential for other narrow-spectrum β-lactamases to function as CHDLs.
Main Methods:
- Expression of OXA-2 and OXA-10 in Escherichia coli and Acinetobacter baumannii.
- Assessment of antibiotic resistance patterns in engineered bacterial strains.
- Kinetic studies of OXA-2 and OXA-10 activity against various carbapenem antibiotics.
Main Results:
- OXA-2 and OXA-10 conferred narrow-spectrum resistance in E. coli.
- In A. baumannii, these enzymes exhibited extended-spectrum resistance, including to carbapenems.
- Kinetic analysis showed catalytic efficiencies comparable to known carbapenemases.
Conclusions:
- The classification of OXA-2 and OXA-10 as narrow-spectrum β-lactamases is inaccurate.
- These enzymes function as carbapenem-hydrolyzing class D β-lactamases (CHDLs) in A. baumannii.
- Other enzymes currently considered non-carbapenemases may possess CHDL activity.
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