Revising the definition of extensively drug-resistant tuberculosis

Challenges & Solutions for Recent Advancements in Multi-Drugs Resistance Tuberculosis: A Review

In MDR-TB, mycobacterium is resistant to battlefront drugs like rifampicin and isoniazid. Now it's an urgent global challenge for treatment & diagnosis because more than 50% of drugs are resistant. Till today's information, 5 reasons are liable for MDR: (1) Errors of physicians/patients in therapy management, (2) Complexity and poor vascularization of granulomatous lesions, which obstruct drug distribution to some sites, leading to resistance development, (3) Intrinsic drug resistance of tubercle bacilli, (4) Formation of non-replicating, drug-tolerant bacilli inside the granulomas, (5) Development of mutations in Mtb genes, which are the foremost important molecular mechanisms of resistance. the most contribution of this work is a brief & clear explanation of things chargeable for resistant development, and recent diagnostic & treatment methods for MDR-TB. This study shall help researchers & scientists to develop replacement rapid diagnostic tools, drugs, and treatment protocols.

Evidence-based Definition for Extensively Drug-resistant Tuberculosis

RATIONALE

Until 2020, extensively drug-resistant tuberculosis (XDR-TB) was defined as resistance to rifampicin and isoniazid (multidrug-resistant tuberculosis, MDR-TB), any fluoroquinolone (FQ) and any second-line injectable drug (SLID). In 2019 the World Health Organization issued new recommendations for managing patients with drug-resistant tuberculosis, substantially limiting the role of SLID in MDR-TB treatment and thus putting that XDR-TB definition into question.

OBJECTIVE

To propose an up-to-date definition for XDR-TB.

METHODS

We used a large dataset to assess treatment outcomes for MDR-TB patients exposed to any type of longer regimen. We included patients with bacteriologically confirmed MDR-TB and known FQ and SLID resistance results. We did logistic regression to estimate adjusted odds ratios (aORs) for unfavourable treatment outcome (failure, relapse, death, loss-to-follow-up) by resistance pattern (FQ, SLID) and Group A drug use (moxifloxacin/levofloxacin, linezolid, bedaquiline).

MEASUREMENTS AND MAIN RESULTS

We included 11,666 patients with MDR-TB; 4653 (39.9%) had an unfavourable treatment outcome. Resistance to FQs increased the odds of an unfavourable treatment outcome (aOR 1.91; 95% confidence interval [95%CI] 1.63-2.23). Administration of bedaquiline and/or linezolid improved treatment outcomes regardless of resistance to FQ and/or SLID. Among XDR-TB patients, compared to persons receiving no Group A drug, aORs for unfavourable outcome were 0.37 (95%CI 0.20-0.69) with linezolid only, 0.40 (95%CI 0.21-0.77) with bedaquiline only, and 0.21 (95%CI 0.12-0.38) with both.

CONCLUSIONS

Our study supports a new definition of XDR-TB as MDR plus additional resistance to FQ plus bedaquiline and/or linezolid, and helps assess the adequacy of this definition for surveillance and treatment choice.NOTE: This article has been updated on July 16, 2021. When it was initially posted on June 9, 2021, the name of one of the coauthors, Dr. Christian Lienhardt, was inadvertently omitted. This version includes Dr. Lienhardt's affilations and contributions; the affiliations have therefore been renumbered.

Hydroxylation of Antitubercular Drug Candidate, SQ109, by Mycobacterial Cytochrome P450

Spreading of the multidrug-resistant (MDR) strains of the one of the most harmful pathogen Mycobacterium tuberculosis (Mtb) generates the need for new effective drugs. SQ109 showed activity against resistant Mtb and already advanced to Phase II/III clinical trials. Fast SQ109 degradation is attributed to the human liver Cytochrome P450s (CYPs). However, no information is available about interactions of the drug with Mtb CYPs. Here, we show that Mtb CYP124, previously assigned as a methyl-branched lipid monooxygenase, binds and hydroxylates SQ109 in vitro. A 1.25 Å-resolution crystal structure of the CYP124-SQ109 complex unambiguously shows two conformations of the drug, both positioned for hydroxylation of the ω-methyl group in the trans position. The hydroxylated SQ109 presumably forms stabilizing H-bonds with its target, Mycobacterial membrane protein Large 3 (MmpL3). We anticipate that Mtb CYPs could function as analogs of drug-metabolizing human CYPs affecting pharmacokinetics and pharmacodynamics of antitubercular (anti-TB) drugs.

Drug-Resistant Tuberculosis: A Glance at Progress and Global Challenges

Multidrug-resistant Mycobacterium tuberculosis remains a major public health threat; its management poses a significant economic burden. Treatment requires a programmatic approach with access to laboratory services, second-line medications, and adequate clinical resources. In recent years, we have seen rapid developments in diagnostic techniques with whole genome sequencing-based drug susceptibility prediction now in reach, an array of new drugs that transform treatment regimens to purely oral formulations, and a steady stream of multinational trials that inform us about most efficient combinations. Our hope is that the current momentum keeps the ambitious goal to end tuberculosis in 2030 in reach.

The Lancet Respiratory Medicine Commission: 2019 update: epidemiology, pathogenesis, transmission, diagnosis, and management of multidrug-resistant and incurable tuberculosis

The Lancet Respiratory Medicine Commission on drug-resistant tuberculosis was published in 2017, which comprehensively reviewed and provided recommendations on various aspects of the disease. Several key new developments regarding drug-resistant tuberculosis are outlined in this Commission Update. The WHO guidelines on treating drug-resistant tuberculosis were updated in 2019 with a reclassification of second line anti-tuberculosis drugs. An injection-free MDR tuberculosis treatment regimen is now recommended. Over the past 3 years, advances in treatment include the recognition of the safety and mortality benefit of bedaquiline, the finding that the 9-11 month injectable-based 'Bangladesh' regimen was non-inferior to longer regimens, and promising interim results of a novel 6 month 3-drug regimen (bedaquiline, pretomanid, and linezolid). Studies of explanted lungs from patients with drug-resistant tuberculosis have shown substantial drug-specific gradients across pulmonary cavities, suggesting that alternative dosing and drug delivery strategies are needed to reduce functional monotherapy at the site of disease. Several controversies are discussed including the optimal route of drug administration, optimal number of drugs constituting a regimen, selection of individual drugs for a regimen, duration of the regimen, and minimal desirable standards of antibiotic stewardship. Newer rapid nucleic acid amplification test platforms, including point-of-care systems that facilitate active case-finding, are discussed. The rapid diagnosis of resistance to other drugs, (notably fluoroquinolones), and detection of resistance by targeted or whole genome sequencing will probably change the diagnostic landscape in the near future.

Drug-Resistant Tuberculosis 2020: Where We Stand

The control of tuberculosis (TB) is hampered by the emergence of multidrug-resistant (MDR) Mycobacterium tuberculosis (Mtb) strains, defined as resistant to at least isoniazid and rifampin, the two bactericidal drugs essential for the treatment of the disease. Due to the worldwide estimate of almost half a million incident cases of MDR/rifampin-resistant TB, it is important to continuously update the knowledge on the mechanisms involved in the development of this phenomenon. Clinical, biological and microbiological reasons account for the generation of resistance, including: (i) nonadherence of patients to their therapy, and/or errors of physicians in therapy management, (ii) complexity and poor vascularization of granulomatous lesions, which obstruct drug distribution to some sites, resulting in resistance development, (iii) intrinsic drug resistance of tubercle bacilli, (iv) formation of non-replicating, drug-tolerant bacilli inside the granulomas, (v) development of mutations in Mtb genes, which are the most important molecular mechanisms of resistance. This review provides a comprehensive overview of these issues, and releases up-dated information on the therapeutic strategies recently endorsed and recommended by the World Health Organization to facilitate the clinical and microbiological management of drug-resistant TB at the global level, with attention also to the most recent diagnostic methods.

Carbon nanomaterials: a new way against tuberculosis

Introduction: Tuberculosis (TB) remains one of the most alarming worldwide infectious diseases primarily in low-income countries, where the infection shows a higher and unvaried prevalence. In the last years, the emergence and spread of Mycobacterium tuberculosis (Mtb) strains resistant to first-line anti-TB drugs are the cause of major concern and prompted the implementation of new treatments, including the development of new drugs and the repurposing of old ones. Areas covered: In this review, we discuss solutions against TB based on nanomaterials (NMTs), alone or combined with current anti-TB drugs. We will summarize drug delivery platforms tested in in vivo or in vitro models and their activity against mycobacteria. We will describe how the new nanotechnologies based on carbon nanomaterials, like carbon nanotubes and graphene oxide are now facing the panorama of the medical fight against TB. Expert opinion: We foresee that in the next decade carbon nanomaterials will be at the forefront in fighting emerging antibiotic-resistant Mtb strains by shortening treatment periods, reducing adverse effects and mitigating antibiotic use. However, toxicity and biodegradation studies should be done prior to the clinical translation of carbon nanomaterials.

Management of drug-resistant tuberculosis

Drug-resistant tuberculosis is a major public health concern in many countries. Over the past decade, the number of patients infected with Mycobacterium tuberculosis resistant to the most effective drugs against tuberculosis (ie, rifampicin and isoniazid), which is called multidrug-resistant tuberculosis, has continued to increase. Globally, 4·6% of patients with tuberculosis have multidrug-resistant tuberculosis, but in some areas, like Kazakhstan, Kyrgyzstan, Moldova, and Ukraine, this proportion exceeds 25%. Treatment for patients with multidrug-resistant tuberculosis is prolonged (ie, 9-24 months) and patients with multidrug-resistant tuberculosis have less favourable outcomes than those treated for drug-susceptible tuberculosis. Individualised multidrug-resistant tuberculosis treatment with novel (eg, bedaquiline) and repurposed (eg, linezolid, clofazimine, or meropenem) drugs and guided by genotypic and phenotypic drug susceptibility testing can improve treatment outcomes. Some clinical trials are evaluating 6-month regimens to simplify management and improve outcomes of patients with multidrug-resistant tuberculosis. Here we review optimal diagnostic and treatment strategies for patients with drug-resistant tuberculosis and their contacts.

Tuberculosis

Tuberculosis remains the leading cause of death from an infectious disease among adults worldwide, with more than 10 million people becoming newly sick from tuberculosis each year. Advances in diagnosis, including the use of rapid molecular testing and whole-genome sequencing in both sputum and non-sputum samples, could change this situation. Although little has changed in the treatment of drug-susceptible tuberculosis, data on increased efficacy with new and repurposed drugs have led WHO to recommend all-oral therapy for drug-resistant tuberculosis for the first time ever in 2018. Studies have shown that shorter latent tuberculosis prevention regimens containing rifampicin or rifapentine are as effective as longer, isoniazid-based regimens, and there is a promising vaccine candidate to prevent the progression of infection to the disease. But new tools alone are not sufficient. Advances must be made in providing high-quality, people-centred care for tuberculosis. Renewed political will, coupled with improved access to quality care, could relegate the morbidity, mortality, and stigma long associated with tuberculosis, to the past.