Drug-resistant tuberculosis (TB) is estimated to account for approximately 30% of annual deaths due to antimicrobial resistance (AMR) [ 1 ]. This is mainly due to mortality of approximately 44% caused by multidrug-resistant (MDR) TB (defined by resistance to isoniazid and rifampicin) [ 2 ]. Therefore, accurately diagnosing AMR for TB is crucial not only to select the most effective regimen with the least side effects but also to minimize costs (e.g. the median cost to treat MDR-TB is $6430 compared with $973 for drug-susceptible TB) [ 2 ]. Owing to the slow growth rate of the Mycobacterium tuberculosis complex (MTBC), this is increasingly achieved using genotypic approaches [ 3 ]. However, phenotypic antimicrobial susceptibility testing (pAST) is still needed to correlate the presence of mutations and their phenotypic expression, especially for new anti-TB agents for which resistance mutations are unknown.
- Drug susceptibility testing