Availability of drug susceptibility testing to new/re-purposed anti-tuberculosis drugs: a TBnet study

<b>Introduction:</b> New (bedaquiline, delamanid) and re-purposed (linezolid, clofazimine) drugs play a crucial role in treating rifampicin-resistant tuberculosis (RR-TB) and defining resistance levels. Drug susceptibility testing (DST) for these drugs is key to monitor and manage drug resistance. <b>Objective:</b> To assess the availability of DST for new/re-purposed drugs across Europe. <b>Methods:</b> In 2020, a cross-sectional online survey was sent to one&nbsp;TB Network European Trialsgroup (TBnet) country representative&nbsp;for each WHO Europe region country, excluding Central Asia. The survey investigated availability of phenotypic/genotypic DST, and numbers of diagnosed/treated RR-TB patients with resistance to new/re-purposed drugs from 2015 to 2019. <b>Results:</b> Overall, 40 representatives out of 45 (89%) responded to the survey. Phenotypic or genotypic DST was available for all four drugs in 38% of countries, and for none in 25%, mostly in Eastern Europe (Figure). DST availability was lower for delamanid (45%), bedaquiline (50%), and clofazimine (55%), than for linezolid (68%). Among countries with DST capacity, documented resistance was reported between 52% (linezolid) and 38% (bedaquiline). Most patients (83%) with phenotypic resistance started treatment. <b>Conclusion:</b> DST for new/re-purposed TB drugs is available in only half of European countries, while drug resistance seems relatively frequent. DST capacity should be increased.