Combining amoxicillin and relebactam provides new therapeutic potential for Mycobacterium abscessus infection

Abstract

22Infections caused by the opportunistic pathogen Mycobacterium abscessus are increasing in 23 prevalence within the cystic fibrosis population. Our limited understanding of this ubiquitous 24 environmental microorganism matched with its intrinsic resistance to most classes of antibiotic, 25including -lactams, has left us with an urgent demand for new, more effective therapeutic 26 interventions. De novo antimicrobial drug discovery is a lengthy process and so we have taken the 27 approach of repurposing known antibiotics in order to provide a rapidly implementable solution to a 28 current problem. Here we report a significant step forward in treatment potential for M. abscessus 29 infection by sensitising the organism to the broad spectrum -lactam antibiotic, amoxicillin, using the 30 non-competitive -lactamase inhibitor, relebactam. We demonstrate by disk diffusion and broth 31 microdilution assay that this combination works synergistically to inhibit M. abscessus. We also 32 demonstrate the direct non-competitive inhibition of the M. abscessus -lactamase, BlaMab using a 33 novel thin-layer chromatography-based assay for -lactamase inhibition, which is subsequently 34 kinetically validated by spectrophotometric assay using the nitrocefin reporter assay. Finally, we 35 demonstrate the in vitro efficacy of this combination against a collection of M. abscessus clinical 36 isolates, demonstrating the significant therapeutic potential of the amoxicillin and relebactam 37 combination. 38 39 Introduction: 40