From Bench to Clinic: A Nitroreductase Rv3368c-Responsive Cyanine-Based Probe for the Specific Detection of Live <i>Mycobacterium tuberculosis</i>

Tuberculosis (TB), characterized by high mortality and low diagnosis, is caused by a single pathogen, Mycobacterium tuberculosis ( Mtb ). Imaging tools that can be used to track Mtb without pre-labeling and to diagnose live Mtb in clinical samples can shorten the gap between bench and clinic, fuel the development of novel anti-TB drugs, strengthen TB prevention, and improve patient treatment. In this study, we report an unprecedented novel nitroreductase-responsive cyanine-based fluorescent probe ( Cy3-NO 2 -tre ) that rapidly and specifically labels Mtb and detects it in clinical samples. Cy3-NO 2 -tre generated fluorescence after activation by a specific nitroreductase, Rv3368c, which is conserved in the Mycobacteriaceae . Cy3-NO 2 -tre effectively imaged mycobacteria within infected host cells, tracked the infection process, and visualized Mycobacterium smegmatis being endocytosed by macrophages. Cy3-NO 2 -tre also detected Mtb in the sputum of patients with TB and exhibited excellent photostability. Furthermore, the Cy3-NO 2 -tre /auramine O percentage change within 7 ± 2 days post drug treatment in the sputum of inpatients was closely correlated with the reexamination results of the chest computed tomography, strongly demonstrating the clinical application of Cy3-NO 2 -tre as a prognostic indicator in monitoring the therapeutic efficacy of anti-TB drugs in the early patient care stage.