Drug-resistant tuberculosis treatment

Rifampicin-resistant TB (RR-TB): TB caused by M. tuberculosis strains resistant to rifampicin. These 
strains may be susceptible or resistant to isoniazid (i.e. MDR-TB), or resistant to other first-line or 
second-line TB medicines. In these guidelines and elsewhere, MDR-TB and RR-TB cases are often 
grouped together as MDR/RR-TB and are eligible for treatment with MDR-TB
regimens.
Rifampicin-susceptible, isoniazid-resistant TB (Hr-TB): caused by M. tuberculosis strains resistant 
to isoniazid and susceptible to
rifampicin.
Second-line TB medicine (or drug): an agent used for the treatment of drug-resistant TB. First-
line TB medicines used to treat drug-susceptible TB – ethambutol, isoniazid and pyrazinamide – may 
also be used in MDR-TB regimens. Streptomycin is now considered a second-line TB medicine and is 
used only as a substitute for amikacin in the following situations: when amikacin is not available, when 
there is confirmed resistance to amikacin but confirmed susceptibility to streptomycin, and when an 
all-oral regimen cannot be
constituted.
Serious adverse events: is an adverse event that leads to death or a life-threatening experience, 
to hospitalization or prolongation of hospitalization, to persistent or significant disability, or to a 
congenital anomaly. Serious adverse events that do not immediately result in one of these outcomes 
but that require an intervention to prevent such an outcome from happening are included. Serious 
adverse events may require a drastic intervention, such as termination of the drug suspected of 
having caused the
event.
Severe extrapulmonary TB: presence of miliary TB or TB meningitis. In children aged under 
15 years, extrapulmonary forms of disease other than lymphadenopathy (peripheral nodes or isolated 
mediastinal mass without compression) are considered as
severe.