Three new inhibitors of class A β-lactamases evaluated by molecular docking and dynamics simulations methods: relebactam, enmetazobactam, and QPX7728

Antibiotic-resistant Acinetobacter baumannii, Pseudomonas aeruginosa, Mycobacterium tuberculosis, Staphylococcus aureus, and Enterobacterales infections are serious global health problems, and class A β-lactamases are one mechanism that leads to antibiotic resistance. QPX7728, relebactam, and enmetazobactam are new β-lactamase inhibitors to combat β-lactam resistance. in silico approach was used in the current study to find which of the three inhibitors would be more effective for all class A β-lactamases and to reveal molecular insights into the differences between their binding energies. The mutations in conserved residues of the active sites of β-lactamases were defined using BLDB and Clustal Omega. FastME and MMseq2 were used for cluster and phylogeny analysis. 3D protein structure models for β-lactamases were built using SWISS-MODEL. ERRAT and Galaxy Web Server were used to verify 42 β-lactamase protein structures. QPX7728, relebactam, and enmetazobactam were docked to β-lactamases by using AutoDock 4.2. The TEM76-relebactam, CTX-M-81-relebactam, TEM-76-enmetazobactam, and CTX-M-200-enmetazobactam complexes were simulated by molecular dynamics method for 500 ns. Based on molecular docking results, relebactam and QPX7728 were more favorable inhibitors for serine A β-lactamases. A 2D representation of the interactions between ligands and β-lactamases showed that S235, hydrogen bonded with TEM-76, might play a role in inhibitor design. A 500-ns MD analysis of complexes indicated that distance from S70, stability in the enzyme active cavity, and high atomic displacement would account for a significant difference in inhibitor binding affinity.

Third-generation cephalosporin resistance in clinical isolates of Enterobacterales collected between 2016-2018 from USA and Europe: genotypic analysis of β-lactamases and comparative in vitro activity of cefepime/enmetazobactam

OBJECTIVES

This study aimed to investigate third-generation cephalosporin (3GC) resistance determinants [extended-spectrum β-lactamases (ESBLs), AmpC β-lactamases and OXA-type β-lactamases] in contemporary clinical Enterobacterales isolates and to determine the in vitro activity of β-lactams and β-lactam/β-lactamase inhibitor combinations, including the investigational combination of cefepime and the novel β-lactamase inhibitor enmetazobactam.

METHODS

Antibacterial susceptibility of 7168 clinical Enterobacterales isolates obtained between 2016-2018 from North America and Europe was determined according to CLSI guidelines. Phenotypic resistance to the 3GC ceftazidime (MIC ≥ 16 µg/mL) and/or ceftriaxone (MIC ≥ 4 µg/mL) but retaining susceptibility to meropenem (MIC ≤ 1 µg/mL) was determined. β-Lactamase genotyping was performed on clinical isolates with ceftazidime, ceftriaxone, cefepime or meropenem MIC ≥ 1 µg/mL.

RESULTS

Phenotypic resistance to 3GCs occurred in 17.5% of tested isolates, whereas 2.1% of isolates were resistant to the carbapenem meropenem. Within the 3GC-resistant subgroup, 60.1% (n = 752) of isolates encoded an ESBL, 25.6% (n = 321) encoded an AmpC-type β-lactamase and 0.9% (n = 11) encoded an OXA-type β-lactamase. Susceptibility of the subgroup to piperacillin/tazobactam (57.5%) and ceftolozane/tazobactam (71.3%) was <90% based on breakpoints established by the CLSI. Projected susceptibility to cefepime/enmetazobactam was 99.6% when applying the cefepime susceptible, dose-dependent breakpoint of 8 µg/mL. Against ESBL-producing isolates (n = 801) confirmed by genotyping, only susceptibility to meropenem (96.0%) and cefepime/enmetazobactam (99.9%) exceeded 90%.

CONCLUSION

This study describes the antibacterial activity of important therapies against contemporary 3GC-resistant clinical Enterobacterales isolates and supports the development of cefepime/enmetazobactam as a carbapenem-sparing option for ESBL-producing pathogens.

Liquid chromatography-tandem mass spectrometry for the simultaneous quantitation of enmetazobactam and cefepime in human plasma

A simple ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for the simultaneous analysis enmetazobactam (also known as AAI101) and cefepime in human plasma. Sample preparation was based on protein precipitation with acetonitrile. Separation was performed on Acquity BEH HILIC column (50 mm × 2.1 mm, 1.7 μm) with a mobile phase containing ammonium formate in water and acetonitrile. The analytes were analyzed with the corresponding isotopically labeled internal standards and were detected in multiple reactions monitoring (MRM) using API 5000 triple-quadrupole mass spectrometer with electrospray (ESI) source operating in positive ion mode. The calibration curves were linear over the selected ranges (r > 0.9970 for both analytes). The intra and inter-assay precision of the Quality Control samples showed CV ≤ 15% and the accuracy was within 85 and 115% in all cases for both compounds. The lower limit of quantification was 0.05 μg/mL for enmetazobactam and 0.5 μg/mL for cefepime.