HIV/AIDS Glossary

A relatively rare type of multidrug-resistant tuberculosis (MDR-TB). Extensively drug-resistant tuberculosis (XDR-TB) occurs when a Mycobacterium tuberculosis strain becomes resistant to the first-line anti-TB drugs isoniazid and rifampin, plus any fluoroquinolone and at least one of the three second-line injectable drugs. XDR-TB progresses more rapidly and is more severe in people who have both XDR-TB and HIV than in people who have only XDR-TB.