XDRTB

XDR-TB stands for extensively drug-resistant tuberculosis. It refers to strains of Mycobacterium tuberculosis that are resistant to at least isoniazid and rifampin (the defining features of multidrug-resistant TB), plus resistance to any fluoroquinolone and at least one of the three second-line injectable drugs (amikacin, kanamycin, or capreomycin). This resistance profile makes XDR-TB substantially harder to treat than drug-susceptible TB or MDR-TB.

Diagnosis relies on comprehensive drug-susceptibility testing of both first- and second-line drugs. Traditional culture-based testing is augmented by molecular methods such as line probe assays and whole-genome sequencing to determine resistance to fluoroquinolones and second-line injectables. While tests like Xpert MTB/RIF can detect rifampin resistance, they do not by themselves identify XDR-TB; DST for multiple drugs is required.

Treatment for XDR-TB is complex, lengthy, and associated with greater toxicity than drug-susceptible TB. Regimens typically involve combinations of second-line drugs and may include newer or repurposed agents such as bedaquiline, linezolid, and pretomanid, used in specific, guideline-supported regimens. The goal is to maximize efficacy while managing adverse effects, with close monitoring for toxicity. Outcomes vary by individual factors, including HIV status, prior treatment, and adherence.

Public health management emphasizes rapid diagnosis, effective infection control, completion of tailored regimens, and monitoring to prevent transmission. XDR-TB remains most prevalent in settings with delays in diagnosis or suboptimal treatment; efforts focus on expanding DST access, ensuring treatment adherence, and advancing research into shorter, safer, and more effective regimens.