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

Abstract

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.

Siderophore-based fluorescent probes, such as N14G, have been developed for the detection of mycobacteria utilizing an active heterodimeric ABC transporter (IrtAB transporter). These probes exhibit ultrasensitivity with detection concentrations as low as 1−10 nM, yield results within a rapid 5 min incubation period, and possess a limit of detection of 34 CFU for the wild-type H37Rv strain of Mycobacterium tuberculosis. N14G and N14G-Fe are ultrasensitive fluorescent probes that utilize the IrtAB transporter for the specific detection of mycobacteria and the diagnosis of clinical sputum samples at concentrations ranging from 1 to 10 nM.