Synergistic Effects of Sulopenem in Combination with Cefuroxime or Durlobactam againstMycobacterium abscessus

Abstract

Mycobacterium abscessus(Mab) affects patients with immunosuppression, Cystic Fibrosis (CF), or underlying structural lung diseases. Additionally,Mabposes clinical challenges due to its resistance to multiple antibiotics. Herein, we investigated the synergistic effect of dual β-lactams [sulopenem and cefuroxime (CXM)] or the combination of sulopenem and CXM with a β-lactamase inhibitors [BLI; avibactam (AVI) or durlobactam (DUR)]. The sulopenem-CXM combination yielded low minimum inhibitory concentration MIC values for 54 clinicalMabisolates and ATCC19977 (MIC50and MIC90≤ 0.25 μg/mL). Similar synergistic effects were observed in time-kill studies conducted at concentrations achievable in clinical settings. Sulopenem-CXM outperformed monotherapy, yielding ∼1.5 Log10CFU/mL reduction during 10 days. Addition of BLIs enhanced this antibacterial effect, resulting in additional reduction of CFUs (∼3 Log10for sulopenem-CXM and AVI and ∼4 Log10for sulopenem-DUR). Exploration of the potential mechanisms of the synergy focused on their interactions with L,D-transpeptidases (LDTs; LDTMab1–LDTMab4), Penicillin-Binding-Protein B (PBP-B), and D,D-Carboxypeptidase (DDC). Acyl complexes identified via mass spectrometry analysis, demonstrated the binding of sulopenem with LdtMab2-LdtMab4, DDC, and PBP B, and CXM with LdtMab2and PBP-B. Molecular docking suggested formation of a covalent adduct between sulopenem and LdtMab2after the nucleophilic attack of the cysteine residue at the β-lactam carbonyl carbon, leading to the cleavage of the β-lactam ring, and the establishment of a thioester bond linking the LdtMab2with sulopenem. In conclusion, we demonstrated the biochemical basis of the synergy of sulopenem-CXM with or without BLI. These findings potentially broaden selection of oral therapeutic agents to combatMab.