Dataset Information

Meropenem-Vaborbactam Resistance Selection, Resistance Prevention, and Molecular Mechanisms in Mutants of KPC-Producing Klebsiella pneumoniae.

ABSTRACT: Vaborbactam (formerly RPX7009) is a new ?-lactamase inhibitor based on a cyclic boronic acid pharmacophore with potent inhibitory activity against Klebsiella pneumoniaecarbapenemases (KPC). It has been developed in combination with meropenem. The objective of these studies was to identify the concentrations of both agents associated with the selection or prevention of single-step mutations leading to reduced sensitivity to the combination and to characterize the selected mutations. Eighteen strains of KPC-producing Klebsiella pneumoniae with various degrees of sensitivity to meropenem (MICs, 8 to 512 ?g/ml) and meropenem-vaborbactam (MICs, ?0.06 to 32 ?g/ml) and preexisting resistance mechanisms were selected from a worldwide collection of isolates recovered from surveillance studies, emphasizing strains for which MICs were in the upper range of the meropenem-vaborbactam MIC distribution. Meropenem and vaborbactam at 8 ?g/ml each suppressed the drug resistance mutation frequency to <1 × 10-8 in 77.8% (14/18) of strains, and all strains were inhibited when the meropenem concentration was increased to 16 ?g/ml. Mutants selected at lower drug concentrations showed phenotypes associated with previously described carbapenem resistance mechanisms, including ompK36 inactivation in mutants selected from OmpK36-proficient strains and an increased blaKPC gene copy number in strains with partially functional ompK36 No mutations in the coding region of blaKPC were identified. These data indicate that the selection of mutants with reduced sensitivity to meropenem-vaborbactam from KPC-producing Klebsiella pneumoniae strains is associated with previously described mechanisms involving porin mutations and the increase in the blaKPC gene copy number and not changes in the KPC enzyme and can be prevented by the drug concentrations achieved with optimal dosing of the combination.

SUBMITTER: Sun D

PROVIDER: S-EPMC5700310 | biostudies-literature | 2017 Dec

REPOSITORIES: biostudies-literature

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Publications

Meropenem-Vaborbactam Resistance Selection, Resistance Prevention, and Molecular Mechanisms in Mutants of KPC-Producing Klebsiella pneumoniae.

Sun Dongxu D Rubio-Aparicio Debora D Nelson Kirk K Dudley Michael N MN Lomovskaya Olga O

Antimicrobial agents and chemotherapy 20171122 12

Vaborbactam (formerly RPX7009) is a new β-lactamase inhibitor based on a cyclic boronic acid pharmacophore with potent inhibitory activity against Klebsiella pneumoniaecarbapenemases (KPC). It has been developed in combination with meropenem. The objective of these studies was to identify the concentrations of both agents associated with the selection or prevention of single-step mutations leading to reduced sensitivity to the combination and to characterize the selec ...[more]

PMID: 29038260

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Project description:Carbapenem-resistant Enterobacteriaceae (CRE) are resistant to most antibiotics, making CRE infections extremely difficult to treat with available agents. Klebsiella pneumoniae carbapenemases (KPC-2 and KPC-3) are predominant carbapenemases in CRE in the United States. Nacubactam is a bridged diazabicyclooctane (DBO) β-lactamase inhibitor that inactivates class A and C β-lactamases and exhibits intrinsic antibiotic and β-lactam "enhancer" activity against Enterobacteriaceae In this study, we examined a collection of meropenem-resistant K. pneumoniae isolates carrying blaKPC-2 or blaKPC-3; meropenem-nacubactam restored susceptibility. Upon testing isogenic Escherichia coli strains producing KPC-2 variants with single-residue substitutions at important Ambler class A positions (K73, S130, R164, E166, N170, D179, K234, E276, etc.), the K234R variant increased the meropenem-nacubactam MIC compared to that for the strain producing KPC-2, without increasing the meropenem MIC. Correspondingly, nacubactam inhibited KPC-2 (apparent Ki [Ki app] = 31 ± 3 μM) more efficiently than the K234R variant (Ki app = 270 ± 27 μM) and displayed a faster acylation rate (k2/K), which was 5,815 ± 582 M-1 s-1 for KPC-2 versus 247 ± 25 M-1 s-1 for the K234R variant. Unlike avibactam, timed mass spectrometry revealed an intact sulfate on nacubactam and a novel peak (+337 Da) with the K234R variant. Molecular modeling of the K234R variant showed significant catalytic residue (i.e., S70, K73, and S130) rearrangements that likely interfere with nacubactam binding and acylation. Nacubactam's aminoethoxy tail formed unproductive interactions with the K234R variant's active site. Molecular modeling and docking observations were consistent with the results of biochemical analyses. Overall, the meropenem-nacubactam combination is effective against carbapenem-resistant K. pneumoniae Moreover, our data suggest that β-lactamase inhibition by nacubactam proceeds through an alternative mechanism compared to that for avibactam.

Dataset Information

Meropenem-Vaborbactam Resistance Selection, Resistance Prevention, and Molecular Mechanisms in Mutants of KPC-Producing Klebsiella pneumoniae.

Publications

Meropenem-Vaborbactam Resistance Selection, Resistance Prevention, and Molecular Mechanisms in Mutants of KPC-Producing Klebsiella pneumoniae.

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