Inhibiting Mycobacterium abscessus Cell Wall Synthesis: Using a Novel Diazabicyclooctane β-Lactamase Inhibitor To Augment β-Lactam Action

mBio. 2022 Feb 22;13(1):e0352921. doi: 10.1128/mbio.03529-21. Epub 2022 Jan 25.

Abstract

Mycobacterium abscessus (Mab) infections are a growing menace to the health of many patients, especially those suffering from structural lung disease and cystic fibrosis. With multidrug resistance a common feature and a growing understanding of peptidoglycan synthesis in Mab, it is advantageous to identify potent β-lactam and β-lactamase inhibitor combinations that can effectively disrupt cell wall synthesis. To improve existing therapeutic regimens to address serious Mab infections, we evaluated the ability of durlobactam (DUR), a novel diazobicyclooctane β-lactamase inhibitor to restore in vitro susceptibilities in combination with β-lactams and provide a biochemical rationale for the activity of this compound. In cell-based assays, susceptibility of Mab subsp. abscessus isolates to amoxicillin (AMOX), imipenem (IMI), and cefuroxime (CXM) was significantly enhanced with the addition of DUR. The triple drug combinations of CXM-DUR-AMOX and IMI-DUR-AMOX were most potent, with MIC ranges of ≤0.06 to 1 μg/mL and an MIC50/MIC90 of ≤0.06/0.25 μg/mL, respectively. We propose a model by which this enhancement may occur, DUR potently inhibited the β-lactamase BlaMab with a relative Michaelis constant (Ki app) of 4 × 10-3 ± 0.8 × 10-3 μM and acylation rate (k2/K) of 1 × 107 M-1 s-1. Timed mass spectrometry captured stable formation of carbamoyl-enzyme complexes between DUR and LdtMab2-4 and Mab d,d-carboxypeptidase, potentially contributing to the intrinsic activity of DUR. Molecular modeling showed unique and favorable interactions of DUR as a BlaMab inhibitor. Similarly, modeling showed how DUR might form stable Michaelis-Menten complexes with LdtMab2-4 and Mab d,d-carboxypeptidase. The ability of DUR combined with amoxicillin or cefuroxime and imipenem to inactivate multiple targets such as d,d-carboxypeptidase and LdtMab2,4 supports new therapeutic approaches using β-lactams in eradicating Mab. IMPORTANCE Durlobactam (DUR) is a potent inhibitor of BlaMab and provides protection of amoxicillin and imipenem against hydrolysis. DUR has intrinsic activity and forms stable acyl-enzyme complexes with LdtMab2 and LdtMab4. The ability of DUR to protect amoxicillin and imipenem against BlaMab and its intrinsic activity along with the dual β-lactam target redundancy can explain the rationale behind the potent activity of this combination.

Keywords: Mycobacterium; Mycobacterium abscessus; antibiotic resistance; antibiotics; bacteria; diazabicyclooctane; durlobactam; inhibitor; β-lactamase inhibitor; β-lactams.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amoxicillin / pharmacology
  • Amoxicillin / therapeutic use
  • Anti-Bacterial Agents / pharmacology
  • Cefuroxime / pharmacology
  • Humans
  • Imipenem / pharmacology
  • Microbial Sensitivity Tests
  • Mycobacterium abscessus*
  • beta-Lactamase Inhibitors / pharmacology
  • beta-Lactamases
  • beta-Lactams* / pharmacology

Substances

  • beta-Lactams
  • beta-Lactamase Inhibitors
  • Anti-Bacterial Agents
  • durlobactam
  • Cefuroxime
  • Imipenem
  • Amoxicillin
  • beta-Lactamases