**9. Preventive measures of MDR-TB through high quality treatment**

Drug-resistant tuberculosis (DR-TB) poses a significant national and international programmatic challenge as well as a significant risk to individuals residing in TB-endemic countries. Only about 30% of the 490,000 people estimated to have developed multidrug-resistant tuberculosis (MDR-TB) (along with an additional 110,000 cases of rifampicin [RMP]-resistant TB) in 2016 had their diagnosis, and only about 25% had their treatment for MDR-TB started, according to the World Health Organisation (WHO) [3, 70].

Although existing drug-resistant cases must also be treated, mathematical modelling reveals that best-practice shortcourse chemotherapy can control isoniazid- or rifampicin-resistant disease while preventing the formation of MDR-TB by obtaining cure rates over 80% in new cases [71]. Focusing on enhanced and quality-controlled bacteriology with universal drug susceptibility testing (DST), quality therapy, removal of healthcare access barriers, and appropriate monitoring and evaluation can avoid the occurrence of MDR-TB in addition to high rates of case-detection and cure (WHO, 2015). This patient-centred strategy is further supported by the International Standards for Tuberculosis Care and its regional variations [72, 73].

Since patients with suspected DR-TB are what drives transmission, the cornerstone of MDR-TB transmission prevention should concentrate on earlier diagnosis and prompt initiation of effective therapy for all DR-TB patients (this includes patients on treatment for DS-TB who have undiagnosed DR-TB as well as those who remain both undiagnosed and untreated)[74]. Making these patients non-infectious will enhance individual outcomes and reduce transmission. A 90% decrease in TB incidence is one of the lofty goals put forth in the WHO's End TB Strategy, which was introduced in 2015 [75]. The End TB Strategy mandates that all individuals being tested for TB, not just those with recognised risk factors for developing DR-TB disease, undergo universal drug susceptibility testing (DST). This method necessitates a large expansion of the use of molecular diagnostics for TB, which allow an early evaluation of treatment resistance at the time of TB diagnosis [70].

Early diagnosis and efficient treatment are essential components of an effective MDR-TB (Multi Drug Resistant Tuberculosis) control approach, similar to DS-TB (Drug Susceptible Tuberculosis). One of the main causes of continued TB transmission is diagnostic delay. Drug susceptibility testing (DST), which is necessary for the diagnosis of drug-resistant tuberculosis (DR-TB), was previously unavailable in the majority of high-prevalence settings until the recent introduction of rapid genotypic DST using GeneXpert MTB/RIF® or Line Probe Assays (such as INNO-LiPA® and Genotype MTBDRsl®) [76]. However, there is still a sizable case detection gap, and it is estimated that in 2014, 75% of MDR-TB patients were unreported [77]. Only 12% of newly diagnosed TB cases with bacteriological confirmation and 58% of TB people who have already received treatment around the world have DST done. The 2016 WHO MDR-TB treatment recommendations include a strong recommendation for universal DST for all TB patients at the time of initial diagnosis [3]. The proposed "F-A-S-T" strategy, which is based on rapid DST (drug susceptibility testing), is

designed to find cases actively by cough monitoring and rapid molecular sputum testing, separate securely, and treat efficiently. This improved guidance is applicable to all settings and age categories [78]. Since these techniques will require significant investment from health systems to become a reality, more study is needed to determine their usefulness [79].
