A non-antibiotic genetic selection system enables near-infrared in vivo imaging and evaluation of antibiotic efficacy for multidrug-resistant Acinetobacter baumannii.

Abstract

Carbapenem-resistant Acinetobacter baumannii (CRAb) is designated by the World Health Organization as a critical priority pathogen, and most clinical CRAb isolates are multidrug-resistant (MDRA). However, an in vivo mouse imaging model of infection using clinical MDRA isolates has not been curated. Using antibiotic resistance genes as plasmid selection markers is incompatible with antimicrobial drug evaluation and prevents their application to MDRA isolates. To overcome this limitation, we constructed a firefly luciferase plasmid using tellurite resistance genes as non-antibiotic selection markers, enabling luminescence in multiple clinical MDRA isolates without altering susceptibility. Using a mouse pneumonia model and near-infrared luciferin derivative (TokeOni), we achieved noninvasive visualization of lung colonization by clinical MDRA isolates. Luminescence dynamics during treatment mirrored the in vitro minimum inhibitory concentration and survival outcomes, providing a therapeutic response readout. This platform overcomes a major bottleneck in MDR pathogen imaging and supports the evaluation of infection dynamics and drug efficacy.