Bioluminescent Mycobacterium abscessus in Galleria mellonella: a preclinical screening tool for antimycobacterial compounds.

Mycobacterium abscessus (Mab) is an emerging pulmonary pathogen with extensive drug resistance, resulting in prolonged multidrug therapy, severe side effects, and cure rates below 50%. The absence of a reliable immunocompetent mouse model and the poor translation of in vitro drug activity to mammalian in vivo efficacy hinder preclinical progress. To address this gap, we developed a novel Galleria mellonella infection model for Mab, combined with bioluminescence imaging (BLI), enabling longitudinal monitoring and quantification of mycobacterial burden. Two double-reporter strains were assessed: a firefly luciferase-expressing strain requiring exogenous luciferin, and an autonomously luminescent Lux strain. Both generated stable signals suitable for longitudinal in vitro and in vivo imaging, with improved in vivo detectability of the luciferase-expressing strain based on its characteristic red-shifted emission spectrum. BLI provided sensitive, early quantification of mycobacterial load and treatment responses, outperforming traditional larval endpoints. This model supports early detection of dose-dependent treatment effects and enables real-time monitoring, thereby highlighting the value of G. mellonella as a rapid, cost-effective complementary preclinical model for screening novel antimycobacterial compounds.