Technical manual for drug susceptibility testing of medicines used in the treatment of tuberculosis

Overview

The effective management of TB and MDR-TB relies upon rapid diagnosis and effective treatment of resistant infections. Culture-based phenotypic drug susceptibility testing (DST) methods are currently the gold standard for drug resistance detection.

Traditionally, DST for MTBC has relied on the testing of a single, critical concentration (CC), which is used to differentiate resistant from susceptible isolates of MTBC and is specific for each anti-TB agent and test method. Laboratory tests of the susceptibility of tubercle bacilli to anti-tuberculosis agents serve three main purposes; firstly, they can be used to guide the choice of chemotherapy to be given to a patient; secondly, they are of value in confirming that drug resistance has emerged when a patient has failed to show a satisfactory response to treatment; and thirdly, can be used for surveillance of emerging drug resistance.

This technical manual focuses on the available DST methods for both first- and second-line anti-TB agents. Culture-based phenotypic DST methods for certain anti-TB medicines are reliable and reproducible, but these methods are time-consuming, require sophisticated laboratory infrastructure, qualified staff and strict quality control. Only indirect DST procedures for anti-TB medicines are included in this document. The methods described are LJ, 7H10 and 7H11 agar and MGIT.