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

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-NO2-tre) that rapidly
and specifically labels Mtb and detects it in clinical
samples. Cy3-NO2-tre generated fluorescence after activation by a specific nitroreductase,
Rv3368c, which is conserved in the Mycobacteriaceae. Cy3-NO2-tre effectively
imaged mycobacteria within infected host cells, tracked the infection
process, and visualized Mycobacterium smegmatis being endocytosed by macrophages. Cy3-NO2-tre also detected Mtb in the sputum of patients with TB and exhibited excellent photostability.
Furthermore, the Cy3-NO2-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-NO2-tre as a prognostic indicator in
monitoring the therapeutic efficacy of anti-TB drugs in the early
patient care stage.