Insights into IrtAB: Iron Transport Facilitates Ultrasensitive Detection of Mycobacteria in Both Cellular and Clinical Environments

Mycobacterium tuberculosis (Mtb) utilizes a heterodimeric ABC transporter (IrtAB) to extract Fe³⁺ ions from host cells. This study demonstrates that ultrasensitive fluorescent probes, achieved through the conjugation of fluorophores with the ligand of IrtAB, N14G and N14G-Fe can detect Mycobacterium smegmatis at concentrations as low as 1-10 nM within an incubation period of less than 5 min. Furthermore, these probes effectively label Mycobacterium bovis Bacille Calmette-Guérin BCG and the wild-type Mtb strain H37Rv at a concentration of 0.1 μM after 10 min of incubation, achieving a limit of detection of 34 Colony-Forming Unit for the wild-type Mtb strain H37Rv. Both N14G and N14G-Fe successfully identified Mtb in sputum samples from patients diagnosed with tuberculosis, exhibiting exceptional fluorescence.