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

Khalid M. Dousa, David C. Nguyen, Sebastian G. Kurz, Magdalena A. Taracila, Christopher R. Bethel, William Schinabeck, Barry N. Kreiswirth, Sheldon T. Brown, W. Henry Boom, Richard S. Hotchkiss, Kenneth E. Remy, Frank J. Jacono, Charles L. Daley, Steven M. Holland, Alita A. Miller, Robert A. Bonomo

Research output: Contribution to journalArticlepeer-review

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 b-lactam and b-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 b-lactamase inhibitor to restore in vitro susceptibilities in combination with b-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 mg/mL and an MIC50/MIC90 of #0.06/ 0.25 mg/mL, respectively. We propose a model by which this enhancement may occur, DUR potently inhibited the b-lactamase BlaMab with a relative Michaelis constant (Ki app) of 4 x 1023 6 0.8 x 1023 mM and acylation rate (k2/K) of 1 x 107 M21 s21. 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 b-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 b-lactam target redundancy can explain the rationale behind the potent activity of this combination.

Original languageEnglish
Article numbere03529
JournalmBio
Volume13
Issue number1
DOIs
StatePublished - Feb 1 2022

Keywords

  • Antibiotic resistance
  • Antibiotics
  • B-lactamase inhibitor
  • B-lactams
  • Bacteria
  • Diazabicyclooctane
  • Durlobactam
  • Inhibitor
  • Mycobacterium
  • Mycobacterium abscessus

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