Biochemical and biophysical characterization of the OXA-48-like carbapenemase OXA-436.

The crystal structure of the class D β-lactamase OXA-436 was solved to a resolution of 1.80 Å. Higher catalytic rates were found at higher temperatures for the clinically important antibiotic imipenem, indicating better adaptation of OXA-436 to its mesophilic host than OXA-48, which is believed to originate from an environmental source.

Structural insights into the enhanced carbapenemase efficiency of OXA-655 compared to OXA-10.

Carbapenemases are the main cause of carbapenem resistance in Gram-negative bacteria. How β-lactamases with weak carbapenemase activity, such as the OXA-10-type class D β-lactamases, contribute to anti-bacterial drug resistance is unclear. OXA-655 is a T26M and V117L OXA-10 variant, recently identified from hospital wastewater.

OXA-48-Mediated Ceftazidime-Avibactam Resistance Is Associated with Evolutionary Trade-Offs.

Infections due to carbapenemase-producing Gram-negative pathogens are associated with limited treatment options and consequently lead to increased mortality and morbidity. In response, combinations of existing β-lactams and novel β-lactamase inhibitors, such as ceftazidime-avibactam (CAZ-AVI), have been developed as alternative treatment options. To understand the development of resistance and evolutionary trajectories under CAZ-AVI exposure, we studied the effects of ceftazidime (CAZ) and CAZ-AVI on the carbapenemase OXA-48 and the epidemic OXA-48 plasmid in Exposure of CAZ and CAZ-AVI resulted in single (P68A) and double (P68A,Y211S) amino acid substitutions in OXA-48, respectively.

The biological assembly of OXA-48 reveals a dimer interface with high charge complementarity and very high affinity.

Many class D β-lactamases form dimers in solution. The functional basis of the dimerization of OXA-48-like class D β-lactamases is not known, but in order to understand the structural requirements for dimerization of OXA-48, we have characterized the dimer interface. Size exclusion chromatography, small angle X-ray scattering (SAXS), and nuclear magnetic resonance (NMR) were used to confirm the oligomeric state of OXA-48 in solution.

Structure, activity and thermostability investigations of OXA-163, OXA-181 and OXA-245 using biochemical analysis, crystal structures and differential scanning calorimetry analysis.

The first crystal structures of the class D β-lactamases OXA-181 and OXA-245 were determined to 2.05 and 2.20 Å resolution, respectively; in addition, the structure of a new crystal form of OXA-163 was resolved to 2.