Drug resistance
Drug resistance among new case
Presence of resistant isolates of M. tuberculosis in patients who either do not report having had any prior anti-tuberculosis treatment (for up to one month) or in countries where adequate documentation is available, when there is no evidence of a previous history of anti-tuberculosis treatment.
Drug resistance among previously treated cases
Presence of resistant isolates of M. tuberculosis in persons who either report having been treated for tuberculosis for one month or more, or in countries where adequate documentation is available, there is evidence of such history.
Drug-resistant tuberculosis (DR-TB)
Tuberculosis caused by a strain of M. tuberculosis complex that is resistant to any anti-tuberculosis drug.
Drug-susceptibility testing (DST)
In vitro testing using phenotypic methods to determine whether M. tuberculosis is susceptible to a particular drug. Also known as antimicrobial susceptibility testing (AST).
Cross-resistance
Resistance to multiple anti-tuberculosis agents caused by a single genetic change (or multiple changes, in case the given resistance mechanisms require several genetic alterations).
Acquired drug resistance
Resistance to one or more anti-tuberculosis drugs which arises during or after the course of treatment.
Sterilizing activity
Ability of a drug to remove all bacteria. In the tuberculosis context it is often referred to the ability to kill slow replicating mycobacteria, once the large bulk of rapidly growing organisms has been killed.
Proportion method
The most common method used for testing the susceptibility of M. tuberculosis complex isolates. In this method, the inoculum used is monitored by testing two dilutions of a culture suspension, and the growth (that is, the number of colonies) on a control medium without an anti-tuberculosis agent is compared with the growth (the number of colonies) present on a medium containing the critical concentration of the anti-tuberculosis drug being tested.
Phenotypic drug susceptibility testing (DST)
Phenotypic testing determines if an isolate is resistant to an anti-tuberculosis drug by evaluating growth (or metabolic activity) in the presence of the drug. Also called conventional DST.
Multidrug-resistant tuberculosis (MDR-TB) regimen
Anti-tuberculosis treatment regimen designed to treat people with rifampicin-resistant (RR) or multidrug-resistant (MDR) tuberculosis.
