Work

Loss-of-Function Mutations in the Penicillin-Binding Protein PonA1 Confer Agar-Dependent Resistance to Durlobactam in Mycobacterium abscessus

Year: 2025

Type: article

Abstract: Background: Infections caused by the multidrug-resistant pathogen Mycobacterium abscessus (Mab) are notoriously difficult to treat. The novel β-lactamase inhibitor durlobactam, in combination with β-lactams, shows potent bactericidal activity against Mab, but the potential for acquired resistance remains a clinical concern. Objectives: To identify and characterize mechanisms of acquired resistance to durlobactam in Mab. Methods: In vitro single-step resistance selection was performed by plating wild-type Mab ATCC 19977 and by transcriptional silencing using a CRISPR interference (CRISPRi) system. Minimum inhibitory concentrations (MICs) were determined by both an agar-based method and broth microdilution. Results: Whole-genome sequencing of durlobactam-resistant mutants identified loss-of-function mutations in ponA1, a gene encoding a class A penicillin-binding protein involved in cell wall synthesis. Targeted deletion of ponA1 (ΔponA1) and CRISPRi-mediated knockdown of ponA1 expression both recapitulated the resistance phenotype, resulting in a significant increase in the durlobactam MIC on solid agar media. Strikingly, broth microdilution MICs remained largely unaffected. Conclusions: Inactivation of the peptidoglycan synthase PonA1 is a novel mechanism of resistance to durlobactam in Mab that is phenotypically expressed only during growth on solid surfaces. This finding identifies a specific genetic pathway for resistance and highlights that standard broth-based susceptibility testing could miss clinically relevant resistance mechanisms.

Source: Antibiotics

DOI: 10.3390/antibiotics15010007

Authors: Dereje Abate Negatu, Wassihun Wedajo Aragaw, Min Xie, Véronique A Dartois, Thomas Dick

Institutions: St. Luke's University Health Network, St. Luke's Hospital, Hackensack Meridian Health, Hackensack Meridian School of Medicine

Language: English

Topic: Mycobacterium research and diagnosis

Subfield: Epidemiology

Field: Medicine

Domain: Health Sciences

SDG: Good health and well-being

Open Access status: gold

Estimated APC paid: $3,499