Drug susceptibility testing of second and third line anti-tuberculosis drugs used in the management of extensively drug resistant tuberculosis.

Abstract

Drug resistant tuberculosis is a major contributor to South Africa’s quadruple burden of disease. Management of this infection in a highly HIV endemic area is a constant challenge. There is a paucity of new anti-tuberculosis agents in the developmental and clinical trial phases to address the problem of extensively-drug resistant tuberculosis (XDR-TB). In an attempt to affect a cure in patients with XDR-TB, it has become necessary to re-introduce previously used anti-tuberculosis drugs, as well as antimicrobial agents designed for treatment of non-tuberculosis infections. Whilst these drugs may have previously been tested and shown efficacy in drug susceptible tuberculosis, their activity in XDR TB strains was not tested before introduction for management of XDR-TB in KwaZulu-Natal, South Africa. Drug susceptibility testing (DST) plays an integral role in the diagnosis and treatment options for tuberculosis. It is able to decrease the burden and spread of resistant tuberculosis. However DSTs methods for second line anti –TB drugs (SLDs) and third line anti-TB drugs (TLDs) have not been standardised. Critical concentrations of these anti-TB drugs remain unknown or vary within and between settings thus further hampering the control of TB.