Drug resistant tuberculosis (TB) occurs when the bacteria that cause TB develop the ability to withstand the drugs used to treat the infection. This phenomenon complicates treatment and control efforts, leading to higher morbidity and mortality rates. Drug resistance can occur in two forms: multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB). MDR-TB is resistant to at least isoniazid and rifampicin, the two most potent TB drugs, whereas XDR-TB is resistant to these and additional second-line drugs.
