Multidrug-resistant tuberculosis

Multidrug-resistant tuberculosis (MDR-TB) is tuberculosis caused by bacteria resistant to at least isoniazid and rifampicin, the two most effective first-line drugs.

Mycobacterium tuberculosis: A slow-growing bacterium that causes tuberculosis, usually affecting the lungs but capable of infecting other organs. MDR-TB is caused by strains of this bacterium that resist key antibiotics.
Drug susceptibility testing: Laboratory testing that determines whether a microorganism is susceptible or resistant to particular antimicrobial drugs. Testing can confirm which tuberculosis drugs remain active against an MDR strain.
Isoniazid-resistant tuberculosis: Tuberculosis caused by bacteria resistant to isoniazid but not meeting the definition of multidrug resistance. Isoniazid resistance alone does not qualify as MDR-TB.
Tuberculosis treatment: The use of antimicrobial drugs and supportive care to cure tuberculosis and prevent transmission and relapse. MDR-TB requires a tailored regimen rather than standard first-line treatment.
Antimicrobial resistance: The ability of microorganisms to survive or grow despite exposure to drugs that would normally inhibit or kill them. MDR-TB is a specific form of resistance to antimicrobial drugs.
Linezolid: An oxazolidinone antibiotic that inhibits bacterial protein synthesis and is used in some drug-resistant tuberculosis regimens. It is one option in recommended regimens for eligible patients with MDR-TB.
Rifampicin-resistant tuberculosis: Tuberculosis caused by bacteria resistant to rifampicin, with or without resistance to other drugs. This category includes MDR-TB but also rifampicin resistance without isoniazid resistance.
Tuberculosis contact tracing: The process of identifying and assessing people exposed to someone with infectious tuberculosis. Finding contacts can limit spread from people with MDR-TB and identify exposed individuals needing evaluation.
Isoniazid: A first-line tuberculosis drug that inhibits mycolic-acid production in the bacterial cell wall. Resistance to this drug is one required feature of the MDR-TB definition.
Bedaquiline: A tuberculosis drug that inhibits mycobacterial ATP synthase, disrupting the bacterium's energy production. It is a key medicine in several modern MDR-TB treatment regimens.

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