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There are limited therapeutic options for extensively drug-resistant tuberculosis. In this study from South Korea, linezolid was shown to have some activity in treating resistant tuberculosis; however, its use was associated with clinically significant toxicity. Linezolid (Zyvox, Pfizer) was approved in 2000 for drug-resistant, gram-positive bacterial infections. 1 A member of the oxazolidinone antibiotic class, linezolid inhibits protein synthesis by binding the 23S ribosomal RNA (rRNA) portion of the bacterial 50S ribosomal subunit. 2 In adults, linezolid is administered at a dose of 600 mg twice daily, with phase 3 and postmarketing trials showing an acceptable side-effect and adverse-event profile during the FDA-approved 28 days of therapy. 3 Data on longer-term use are limited, but serious neuropathies (e.g., peripheral and optic neuropathies), myelosuppression, and hyperlactatemia have been observed 4 , 5 and are considered to be related to the inhibition . . .

Important questions exist regarding the ability to treat extensively drug-resistant tuberculosis. In this study involving 48 patients in Peru who had extensively drug-resistant tuberculosis but were not infected with the human immunodeficiency virus, treatment with a structured, comprehensive, community-based approach and aggressive antituberculosis medications (an average of five or six medications per patient) achieved a cure in 29 patients (60%). In 48 patients in Peru who had extensively drug-resistant tuberculosis, treatment with a structured, comprehensive, community-based approach and aggressive antituberculosis medications achieved a cure in 29 patients (60%). Extensively drug-resistant tuberculosis has been reported in 45 countries 1 since it was first described in 2006. This seminal survey found extensively drug-resistant tuberculosis — then defined as Mycobacterium tuberculosis strains with resistance to at least isoniazid, rifampin, and members of three of six classes of second-line drugs — in 10% of multidrug-resistant tuberculosis strains collected on six continents. 2 Isoniazid and rifampin are the anchors of standard first-line therapy. 3 Resistance to these two drugs, which defines multidrug-resistant tuberculosis, is associated with a decreased probability of cure. 4 – 6 Treatment regimens for multidrug-resistant tuberculosis rely on the most active second-line drug classes — . . .

Introduction The urgent need for new treatments for multidrug-resistant tuberculosis (MDR-TB) and pre-extensively drug-resistant tuberculosis (pre-XDR-TB) is evident. However, the classic randomized controlled trial (RCT) approach faces ethical and practical constraints, making alternative research designs and treatment strategies necessary, such as single-arm trials and host-directed therapies (HDTs). Methods Our study adopts a randomized withdrawal trial design for MDR-TB to maximize resource allocation and better mimic real-world conditions. Patients’ treatment regimens are initially based on drug resistance profiles and patient’s preference, and later, treatment-responsive cases are randomized to different treatment durations. Alongside, a single-arm trial is being conducted to evaluate the potential of sulfasalazine (SASP) as an HDT for pre-XDR-TB, as well as another short-course regimen without HDT for pre-XDR-TB. Both approaches account for the limitations in second-line anti-TB drug resistance testing in various regions. Discussion Although our study designs may lack the internal validity commonly associated with RCTs, they offer advantages in external validity, feasibility, and ethical appropriateness. These designs align with real-world clinical settings and also open doors for exploring alternative treatments like SASP for tackling drug-resistant TB forms. Ultimately, our research aims to strike a balance between scientific rigor and practical utility, offering valuable insights into treating MDR-TB and pre-XDR-TB in a challenging global health landscape. In summary, our study employs innovative trial designs and treatment strategies to address the complexities of treating drug-resistant TB, fulfilling a critical gap between ideal clinical trials and the reality of constrained resources and ethical considerations. Trail registration Chictr.org.cn, ChiCTR2100045930. Registered on April 29, 2021.

Background Drug-resistant tuberculosis (DR-TB) remains a threat to global public health, owing to the complexity and delay of diagnosis and treatment. The Global Consortium for Drug-resistant Tuberculosis Diagnostics (GCDD) was formed to develop and evaluate assays designed to rapidly detect DR-TB, so that appropriate treatment might begin more quickly. This paper describes the methodology employed in a prospective cohort study for head-to-head assessment of three different rapid diagnostic tools. Methods Subjects at risk of DR-TB were enrolled from three countries. Data were gathered from a combination of patient interviews, chart reviews, and laboratory testing from each site’s reference laboratory. The primary outcome of interest was reduction in time from specimen arrival in the laboratory to results of rapid drug susceptibility tests, as compared with current standard mycobacterial growth indicator tube (MGIT) drug susceptibility tests. Results Successful implementation of the trial in diverse multinational populations is explained, in addition to challenges encountered and recommendations for future studies with similar aims or populations. Conclusions The GCDD study was a head-to-head study of multiple rapid diagnostic assays aimed at improving accuracy and precision of diagnostics and reducing overall time to detection of DR-TB. By conducting a large prospective study, which captured epidemiological, clinical, and biological data, we have produced a high-quality unique dataset, which will be beneficial for analyzing study aims as well as answering future DR-TB research questions. Reduction in detection time for XDR-TB would be a major public health success as it would allow for improved treatment and more successful patient outcomes. Executing successful trials is critical in assessment of these reductions in highly variable populations. Trial registration ClinicalTrials.gov NCT02170441 .

Therapeutic options for extensively drug-resistant tuberculosis infection are limited. In this post-hoc analysis, a new drug, delamanid, shows some activity in the treatment of XDR-TB. To the Editor: New therapies are needed to address the imminent rise of drug-resistant infections. Delamanid is one of two new drugs approved for the treatment of multidrug-resistant tuberculosis (MDR-TB) in the past 40 years. The clinical evaluation of delamanid included a subgroup of patients with extensively drug-resistant tuberculosis (XDR-TB), which is more difficult to treat than MDR-TB. This evaluation provides an opportunity for a post hoc analysis of outcomes. Our evaluation of delamanid in a single cohort proceeded with a 3-month randomized, controlled trial (a 2-month treatment period with a 1-month follow-up) (Trial 204), a 6-month open-label trial (Trial . . .

Treatment options for highly drug-resistant tuberculosis are limited. In this study in South Africa, a new agent, pretomanid, was combined with bedaquiline and linezolid for a 26-week course to treat extensively drug-resistant and complicated multidrug-resistant pulmonary TB. Although there were toxic effects, 90% of patients had favorable outcomes.

To characterize the genetic determinants of resistance to antituberculosis drugs, we performed a genome-wide association study (GWAS) of 6,465 Mycobacterium tuberculosis clinical isolates from more than 30 countries. A GWAS approach within a mixed-regression framework was followed by a phylogenetics-based test for independent mutations. In addition to mutations in established and recently described resistance-associated genes, novel mutations were discovered for resistance to cycloserine, ethionamide and para -aminosalicylic acid. The capacity to detect mutations associated with resistance to ethionamide, pyrazinamide, capreomycin, cycloserine and para -aminosalicylic acid was enhanced by inclusion of insertions and deletions. Odds ratios for mutations within candidate genes were found to reflect levels of resistance. New epistatic relationships between candidate drug-resistance-associated genes were identified. Findings also suggest the involvement of efflux pumps ( drrA and Rv2688c ) in the emergence of resistance. This study will inform the design of new diagnostic tests and expedite the investigation of resistance and compensatory epistatic mechanisms. A GWAS of multi- and extensively drug-resistant tuberculosis using 6,465 Mycobacterium tuberculosis clinical isolates from more than 30 countries identifies novel mutations associated with resistance. The capacity to detect resistance in particular to ethionamide, pyrazinamide, capreomycin, cycloserine and paraaminosalicylic acid was enhanced by inclusion of insertions and deletions.

Tuberculosis (TB) is the world’s second leading infectious killer. Cases of multidrug-resistant (MDR-TB) and extremely drug-resistant (XDR-TB) have increased globally. Therapeutic drug monitoring (TDM) remains a standard clinical technique for using plasma drug concentrations to determine dose. For TB patients, TDM provides objective information for the clinician to make informed dosing decisions. Some patients are slow to respond to treatment, and TDM can shorten the time to response and to treatment completion. Normal plasma concentration ranges for the TB drugs have been defined. For practical reasons, only one or two samples are collected post-dose. A 2-h post-dose sample approximates the peak serum drug concentration (C max ) for most TB drugs. Adding a 6-h sample allows the clinician to distinguish between delayed absorption and malabsorption. TDM requires that samples are promptly centrifuged, and that the serum is promptly harvested and frozen. Isoniazid and ethionamide, in particular, are not stable in human serum at room temperature. Rifampicin is stable for more than 6 h under these conditions. Since our 2002 review, several papers regarding TB drug pharmacokinetics, pharmacodynamics, and TDM have been published. Thus, we have better information regarding the concentrations required for effective TB therapy. In vitro and animal model data clearly show concentration responses for most TB drugs. Recent studies emphasize the importance of rifamycins and pyrazinamide as sterilizing agents. A strong argument can be made for maximizing patient exposure to these drugs, short of toxicity. Further, the very concept behind ‘minimal inhibitory concentration’ (MIC) implies that one should achieve concentrations above the minimum in order to maximize response. Some, but not all clinical data are consistent with the utility of this approach. The low ends of the TB drug normal ranges set reasonable ‘floors’ above which plasma concentrations should be maintained. Patients with diabetes and those infected with HIV have a particular risk for poor drug absorption, and for drug–drug interactions. Published guidelines typically describe interactions between two drugs, whereas the clinical situation often is considerably more complex. Under ‘real–life’ circumstances, TDM often is the best available tool for sorting out these multi-drug interactions, and for providing the patient safe and adequate doses. Plasma concentrations cannot explain all of the variability in patient responses to TB treatment, and cannot guarantee patient outcomes. However, combined with clinical and bacteriological data, TDM can be a decisive tool, allowing clinicians to successfully treat even the most complicated TB patients.

Tuberculosis (TB) remains the foremost cause of death by an infectious disease globally. Multidrug-resistant or rifampicin-resistant TB (MDR/RR-TB; resistance to rifampicin and isoniazid, or rifampicin alone) is a burgeoning public health challenge in several parts of the world, and especially Eastern Europe, Russia, Asia and sub-Saharan Africa. Pre-extensively drug-resistant TB (pre-XDR-TB) refers to MDR/RR-TB that is also resistant to a fluoroquinolone, and extensively drug-resistant TB (XDR-TB) isolates are additionally resistant to other key drugs such as bedaquiline and/or linezolid. Collectively, these subgroups are referred to as drug-resistant TB (DR-TB). All forms of DR-TB can be as transmissible as rifampicin-susceptible TB; however, it is more difficult to diagnose, is associated with higher mortality and morbidity, and higher rates of post-TB lung damage. The various forms of DR-TB often consume >50% of national TB budgets despite comprising <5–10% of the total TB case-load. The past decade has seen a dramatic change in the DR-TB treatment landscape with the introduction of new diagnostics and therapeutic agents. However, there is limited guidance on understanding and managing various aspects of this complex entity, including the pathogenesis, transmission, diagnosis, management and prevention of MDR-TB and XDR-TB, especially at the primary care physician level. Multidrug-resistant tuberculosis (MDR-TB) is caused by Mycobacterium tuberculosis that is resistant to several first-line drugs. MDR-TB is an increasing public health challenge. In this Primer, Dheda et al. summarize the epidemiology and mechanisms, and discuss diagnosis, management and quality of life of patients with MDR-TB.