First-line Antitubercular Drugs Research Articles

Plasma drug concentrations of 4-drug fixed-dose combination regimen and its efficacy for treatment of pulmonary tuberculosis under National Tuberculosis Elimination Programme: A prospective pilot study

BackgroundThe thrice weekly dosing regimen of DOTS has shown low rifampicin plasma concentrations as an independent risk factor for unfavourable tuberculosis (TB) outcome. With introduction of daily regimen using fixed dose combinations (FDC) under National Tuberculosis Elimination Programme (NTEP) the existence of suboptimal plasma levels of first-line antitubercular drugs and its clinical significance remain poorly understood. MethodWe included a prospective cohort of newly diagnosed pulmonary tuberculosis (PTB) patients receiving 4-FDC daily regimen under NTEP. Plasma concentration at 2 hours (C2h) of each drug was determined after two weeks of treatment using liquid chromatography (LCMS/MS) developed by us. TB card and laboratory reports were reviewed for baseline characteristics and clinical status at 2, 4 and 6 months after the initiation of treatment. At a 1 year follow-up, therapy failure was defined as death or a relapse of tuberculosis. ResultsAmong 40 PTB patients, the C2h post dose plasma concentrations of H, R and E were suboptimal in 25%, 60% and 10% respectively. The C2h of H, R, Z and E were respectively 4.2 ± 2.0, 7.3 ± 2.8, 39.2 ± 8.8 and 3.5 ± 1.2 μg/ml; 60% of the patients had suboptimal plasma concentrations and commonly it was observed with H and R. C2h were lower than expected for at least two drugs i.e. H and R in 25% (10/40) of the patients. Plasma concentration of isoniazid and rifampicin has always been considered important for microbiological response and treatment outcome and low concentrations has been associated with poor treatment response. These patients may require a two year follow up and critical evaluation for prevention of MDR-TB. However, all the TB patients were cured and none of them had recurrence within one year follow up. ConclusionsAll the pulmonary TB patients administering 4-FDC daily regimen under programmatic settings were cured despite the suboptimal levels of isoniaizd and rifampicin. All the patients achieved pyrazinamide plasma levels and probably this could be the reason behind favourable outcome. Further study is required on large sample size with various subset of population to understand the need of therapeutic drug monitoring.

Cytocompatibility and cellular interactions of chondroitin sulfate microparticles designed for inhaled tuberculosis treatment

Tuberculosis remains a leading cause of death, therapeutic failure being mainly due to non-compliance with prolonged treatments, often associated with severe side-effects. New therapeutic strategies are demanded and, considering that the lung is the primary site of infection, direct lung delivery of antibiotics is possibly an effective approach. Therapeutic success in this context depends on suitable carriers that reach the alveoli where Mycobacterium hosts (macrophages) reside, as well as on their ability to promote macrophage capture and intracellular accumulation of drugs. In this work, we propose inhalable polymeric microparticles produced from chondroitin sulfate, a polymer composed by moieties recognized by macrophage receptors. Spray-drying of chondroitin sulfate in combination with two first-line antitubercular drugs (isoniazid and rifabutin) yielded respirable microparticles that evidenced no cytotoxic effects on lung epithelial cells (A549) and macrophages (dTHP1 and J744A.1). The microparticles exhibited tendency for macrophage capture in a dose-dependent manner, which was validated through imaging. High content image analysis revealed that rifabutin induced a dose-dependent increase in phospholipid content of macrophages, which could be prevented by formulation in chondroitin sulfate microparticles. This work provides indications on the potential of chondroitin sulfate carriers to interact with macrophages, thus providing a platform for drug delivery in the context of macrophage intracellular diseases, namely tuberculosis.

Predicting antitubercular drug-induced liver injury and its outcome and introducing a novel scoring system.

Tuberculosis (TB) is a major global health problem, mainly in developing countries. Despite the availability of highly effective first-line antitubercular (ATT) drugs, ATT drug-induced liver injury (ATT DILI) leads to treatment interruption and consequently loss of therapeutic efficacy. In this prospective cohort study from India, all consecutive patients who met inclusion criteria and started on ATT were included. The incidence, risk factors, and outcome of ATT DILI were determined. A clinical prediction score for ATT DILI was derived. A total of 393 patients were included. The incidence of ATT DILI was 9.7% (95% confidence interval 7%-13.2%). HIV infection, daily regimen, disseminated disease, and chronic liver disease were identified as significant risk factors (P < 0.05) for developing DILI. A prediction score derived from the risk factors showed that a score of >5 could predict DILI with a sensitivity of 74% and a specificity of 67%. All-cause mortality in DILI was 4.7%. The incidence of ATT DILI was 9.7% in our cohort with higher incidence among the patients on daily regimen. The study suggests that the combination of risk factors of extensive TB disease, HIV infection, chronic liver disease, and under nutrition increases the vulnerability to DILI, particularly with daily treatment regimen, emphasizing the role of acquired risk factors in the development of DILI.

Synthesis, Self-Assembly, and Biological Activities of Pyrimidine-Based Cationic Amphiphiles

Pyrimidine-based cationic amphiphiles (PCAms), i.e., di-trifluoroacetic acid salts of N1-[1′-(1″,3″-diglycinatoxy-propane-2″-yl)-1′,2′,3′-triazole-4′-yl]methyl-N3-alkylpyrimidines have been synthesized utilizing naturally occurring biocompatible precursors, like glycerol, glycine, and uracil/ thymine in good yields. Synthesized PCAms consist of a hydrophilic head group comprising TFA salt of glyceryl 1,3-diglycinate and hydrophobic tail comprising of C-7 and C-12 N3-alkylated uracil or thymine conjugated via a 4-methylene-1,2,3-triazolyl linker. The physicochemical properties of all PCAms, such as critical aggregation concentration, hydrodynamic diameter, shape, and zeta potential (surface charge) were analyzed. These PCAms were also evaluated for their anti-proliferative and anti-tubercular activities. One of the synthesized PCAm exhibited 4- to 75-fold more activity than first-line anti-tubercular drugs streptomycin and isoniazid, respectively, against the multidrug resistant clinical isolate 591 of Mycobacterium tuberculosis.

The Impact of First-Line Anti-Tubercular Drugs' Pharmacokinetics on Treatment Outcome: A Systematic Review.

BackgroundTuberculosis remains the major public health problem besides tremendous efforts to combat it. Most tuberculosis patients are treated with a standard dose of first-line anti-TB drugs. The cure rate, however, varies from patient to patient. Various factors have been related to anti-TB treatment failure. In recent years, studies associating lower plasma concentrations of anti-TB drugs with poor treatment outcomes are emerging although the results are inconclusive.ObjectiveInvestigate the impact of first-line anti-tubercular drugs pharmacokinetics on treatment outcome.MethodsA systematic search of Pubmed, EMBASE, Web of Science, and the Cochrane Library for articles published in the English language between January 2010 to June 2020 was conducted to identify eligible studies describing associations of first-line anti-tubercular drug pharmacokinetics with treatment outcomes. The primary outcomes considered were pharmacokinetics parameter results and its association with treatment outcome.ResultsThe search identified 1754 articles of which twelve articles; ten prospective observational studies and two controlled clinical trials fulfilled the eligibility criteria. The majority of the studies showed target concentrations for the first-line anti-tubercular drugs below the current standard range. Among the twelve studies, eleven studies assessed rifampicin pharmacokinetics of which eight reported association of drug concentration and treatment outcomes. Similarly, four out of eight and three out of seven reported drug concentration and treatment outcome association for isoniazid and pyrazinamide, respectively. Despite the low plasma concentration, a favorable treatment outcome was achieved for the bulk of the patients. Irrespective of the inconsistency, an increase in exposure to rifampicin improved the outcome, and lower rifampicin, isoniazid, and pyrazinamide concentration are associated with poor outcome. No data are available for ethambutol associating its pharmacokinetics with treatment outcomes.ConclusionThe pharmacokinetics of first-line antitubercular drugs can influence treatment outcomes. Further controlled clinical studies are, however, required to establish these relationships.

Promising Lead Compounds in the Development of Potential Clinical Drug Candidate for Drug-Resistant Tuberculosis.

According to WHO report, globally about 10 million active tuberculosis cases, resulting in about 1.6 million deaths, further aggravated by drug-resistant tuberculosis and/or comorbidities with HIV and diabetes are present. Incomplete therapeutic regimen, meager dosing, and the capability of the latent and/or active state tubercular bacilli to abide and do survive against contemporary first-line and second line antitubercular drugs escalate the prevalence of drug-resistant tuberculosis. As a better understanding of tuberculosis, microanatomy has discovered an extended range of new promising antitubercular targets and diagnostic biomarkers. However, there are still no new approved antitubercular drugs of routine therapy for several decades, except for bedaquiline, delamanid, and pretomanid approved tentatively. Despite this, innovative methods are also urgently needed to find potential new antitubercular drug candidates, which potentially decimate both latent state and active state mycobacterium tuberculosis. To explore and identify the most potential antitubercular drug candidate among various reported compounds, we focused to highlight the promising lead derivatives of isoniazid, coumarin, griselimycin, and the antimicrobial peptides. The aim of the present review is to fascinate significant lead compounds in the development of potential clinical drug candidates that might be more precise and effective against drug-resistant tuberculosis, the world research looking for a long time.

Effect of concomitant HIV infection on adverse drug reactions by first line antitubercular drugs - a case series analysis

The pattern and severity of adverse drug reactions (ADRs) due to first-line anti-tubercular drugs in solely tubercular and TB-HIV co-infected patients could be different due to drug-disease and drug-drug interactions in TB-HIV co-infected patients. Nevertheless, the studies regarding this aspect are very meager. Hence a retrospective appraisal of individual case safety reports (ICSR) due to first-line antitubercular drugs spontaneously submitted to the ADR monitoring center was done for solely tubercular and TB-HIV coinfected patients. Out of eight ICSRs, four had concomitant HIV infection, and two of them were on antiretroviral (ARV) drugs. Co-infected patients showed rare and severe ADRs like optic neuritis, acute renal failure, and drug-induced liver injury (DILI). In contrast, four non-HIV co-infected tubercular patients suffered from comparatively less severe cutaneous reactions and vertigo. A high negative (-0.774) correlation coefficient between HIV co-infection and recovery status found that HIV co-infected patients had low chances of fully recovering. In conclusion, HIV co-infection and ARV drugs can affect the pattern, severity, and recovery status of adverse drug reactions due to first-line antitubercular drugs.

Manifestations of Tuberculosis in Ear, Nose, Throat, Head and Neck Region – A Retrospective Study

Introduction &#x0D; Tuberculosis can involve any organ or site. Otorhinolaryngologist may encounter tuberculosis affecting lymph nodes, ear, larynx, deep neck spaces, salivary glands etc. which can mimic other chronic granulomatous conditions or malignancy. To ensure early diagnosis, it is important to recognize its cardinal signs and symptoms and to be aware of potential pitfalls in diagnosis. This study was done to learn the clinical presentation of tuberculosis in ear, nose, throat and head and neck region, and to assess the effectiveness of various investigations and treatment done for the same.&#x0D; Materials and Methods &#x0D; A retrospective study done in our institution involving 120 patients suffering from tuberculosis in ear, nose, throat and head and neck region who attended pulmonary medicine or ENT OPD or ward between January 2008 to December 2017 that is, 10 years. Study period for data collection and analysis was 1 month.&#x0D; Results&#x0D; Total 120 patients-69 males and 51 females. Most common site was cervical lymph nodes(77.5% patients), followed by larynx(8.3%),middle ear(7.5%),deep neck spaces(2.5%) and salivary glands and nose(1.7% each). Histopathology was highly sensitive(99. 1%).All except one patient responded to first-line antitubercular drugs, the other patient was given treatment for MDR-TB to which he responded.&#x0D; Conclusion&#x0D; Tuberculosis can involve any site in the head and neck region, most common being cervical lymph nodes mainly presenting as neck swelling. Variable nature of manifestations of tuberculosis makes it essential to have high degree of suspicion for early diagnosis.

To Assess the Knowledge and Awareness of Interns Regarding the Management of Tuberculosis as per Recent RNTCP (2017-2025) Guidelines – A Cross Sectional Study

India has been engaged in Tuberculosis control activities for more than 50 years as India is the highest TB burdened country in the world. One such initiative is Revised National Tuberculosis Control Programme (RNTCP) which has been rechristened as National Tuberculosis Elimination Programme (NTEP). The change in name is in line with the larger goal of eliminating the disease by 2025. Objective: The aim of this cross-sectional study is to assess the knowledge and awareness of interns regarding the management of tuberculosis as per recent RNTCP guidelines. Materials &amp; Methods: A structured questionnaire was provided to 111 interns to be filled in a stipulated time. The data collected was analyzed using descriptive statistical parameters and expressed in percentage. Result: Out of a total of 111 interns, 48 (43.24%) were males and 63 (56.75%) were females. Good knowledge was seen among the interns regarding the cardinal symptoms of TB as well as definition of MDR-TB. 92.79% of the participants responded rightly about two sputum samples being taken for diagnosis of TB. Only 76.57% of interns knew the principle of treatment of TB as daily administration of fixed-dose combination of first-line anti-tubercular drugs as per appropriate weight bands and 61.27% of interns were unfamiliar of chemoprophylaxis of tuberculosis according to the recent RNTCP guidelines. Only 71.17% of the participants were updated about the follow-up procedure according to new guidelines. But only 36.93% of participants could answer Cotrimoxazole as the effective drug used in HIV-TB co-infection apart from routine TB drugs to reduce mortality. Conclusion: This survey is providing valuable information that there is deficiency of knowledge among the interns regarding management of tuberculosis according to recent RNTCP guidelines which can lead to treatment failure and thereby causing a hindrance to elimination of TB from our country by 2025

Vibrational Spectroscopic Investigation into Novel Ternary Eutectic Formed between Pyrazinamide, Fumaric Acid, and Isoniazid.

To improve the efficacy of anti-tuberculosis (anti-TB) therapy, drug–drug co-crystallization stands for an alternative approach to settle the tuberculosis problem. Directly co-crystallizing two typical parent anti-TB drugs (pyrazinamide, PZA and isoniazid, INH) into a single binary co-crystal could not be obtained successfully. Multicomponent eutectic are highly effective and useful for enhancing the dissolution rate, bioavailability, and physical stability of the poorly water-soluble active pharmaceutical ingredient (API) drugs, when the attempts of forming a binary co-crystal have failed. Therefore, the ternary eutectic composition conception was proposed in this study, in which fumaric acid (FA) was chosen as the molecule to connect two first-line anti-tubercular drugs. First of all, three starting materials (including PZA, INH, and FA) were grinded at a 1:1:1 molar ratio, the eutectic composition was investigated through vibrational spectroscopic techniques, including terahertz time-domain spectroscopy (THz-TDS) and Raman spectroscopy. Additionally, the density functional theory (DFT) was utilized to simulate the optimized structures and vibrational modes of two possible theoretical eutectic composition forms. The THz absorption spectrum of the theoretical form I shows much more consistency with the experimental results than that of form II. Raman spectra also help to characterize the differences in vibrational modes between the eutectic composition and the starting parent compounds. The results provide us with both structural information and intermolecular hydrogen bonding interactions within specific multicomponent eutectic composition formulations based on Raman and terahertz vibrational spectroscopic techniques in combination with theoretical calculations.

Isoniazid-phytochemical conjugation: A new approach for potent and less toxic anti-TB drug development.

Mycobacterium tuberculosis (Mtb) causes one of the most grievous pandemic infectious diseases, tuberculosis (TB), with long-term morbidity and high mortality. The emergence of drug-resistant Mtb strains, and the co-infection with human immunodeficiency virus, challenges the current WHO-TB stewardship programs. The first-line anti-TB drugs, isoniazid (INH) and rifampicin (RIF), have become extensively obsolete in TB control from chromosomal mutations during the last decades. However, based on clinical trial statistics, the production of well-tolerated anti-TB drug(s) is miserably low. Alternately, semi-synthesis or structural modifications of first-line obsolete antitubercular drugs remain as the versatile approach for getting some potential medicines. The use of any suitable phytochemicals with INH in a hybrid formulation could be an ideal approach for the development of potent anti-TB drug(s). The primary objective of this review was to highlight and analyze available INH-phytochemical hybrid research works. The utilization of phytochemicals through chemical conjugation is a new trend toward the development of safer/non-toxic anti-TB drugs.

Discovery of an Isothiazolinone-Containing Antitubercular Natural Product Levesquamide.

Antitubercular agent levesquamide is a new polyketide-nonribosomal peptide (PK-NRP) hybrid marine natural product isolated from Streptomyces sp. RKND-216. The structure contains a rare isothiazolinone moiety which has only been reported in collismycin SN. Structure elucidation by NMR spectroscopy was a significant challenge due to a deficiency of protons in this aromatic moiety. Therefore, the genome of Streptomyces sp. RKND-216 was sequenced to identify the levesquamide biosynthetic gene cluster (BGC). Analysis of the BGC provided structural insights and guided stable-isotope labeling experiments, which led to the assignment of the fused pyridine-isothiazolinone moiety. The BGC and the labeling experiments provide further insights into the biosynthetic origin of isothiazolinones. Levesquamide exhibited antimicrobial activity in the microplate alamarBlue assay (MABA) and low oxygen recovery assay (LORA) against Mycobacterium tuberculosis H37Rv with minimum inhibitory concentration (MIC) values of 9.65 and 22.28 μM, respectively. Similar activity was exhibited against rifampicin- and isoniazid-resistant M. tuberculosis strains with MIC values of 9.46 and 9.90 μM, respectively. This result suggests levesquamide has a different mode of action against M. tuberculosis compared to the two first-line antitubercular drugs rifampicin and isoniazid. Furthermore, levesquamide shows no cytotoxicity against the Vero cell line, suggesting it may have a useful therapeutic window.

N-Pyrazinoyl Substituted Amino Acids as Potential Antimycobacterial Agents-The Synthesis and Biological Evaluation of Enantiomers.

Tuberculosis is an infectious disease caused by Mycobacterium tuberculosis (Mtb), each year causing millions of deaths. In this article, we present the synthesis and biological evaluations of new potential antimycobacterial compounds containing a fragment of the first-line antitubercular drug pyrazinamide (PZA), coupled with methyl or ethyl esters of selected amino acids. The antimicrobial activity was evaluated on a variety of (myco)bacterial strains, including Mtb H37Ra, M. smegmatis, M. aurum, Staphylococcus aureus, Pseudomonas aeruginosa, and fungal strains, including Candida albicans and Aspergillus flavus. Emphasis was placed on the comparison of enantiomer activities. None of the synthesized compounds showed any significant activity against fungal strains, and their antibacterial activities were also low, the best minimum inhibitory concentration (MIC) value was 31.25 µM. However, several compounds presented high activity against Mtb. Overall, higher activity was seen in derivatives containing l-amino acids. Similarly, the activity seems tied to the more lipophilic compounds. The most active derivative contained phenylglycine moiety (PC-d/l-Pgl-Me, MIC < 1.95 µg/mL). All active compounds possessed low cytotoxicity and good selectivity towards Mtb. To the best of our knowledge, this is the first study comparing the activities of the d- and l-amino acid derivatives of pyrazinamide as potential antimycobacterial compounds.

Formulation and Intracellular Trafficking of Lipid-Drug Conjugate Nanoparticles Containing a Hydrophilic Antitubercular Drug for Improved Intracellular Delivery to Human Macrophages.

Isoniazid is an important first-line antitubercular drug used in the treatment of all major clinical manifestations of tuberculosis, including both pulmonary and cerebral diseases. However, it is associated with significant drawbacks due to its inherent hydrophilic nature, including poor gut permeability and an inability to cross the lipophilic blood–brain barrier, which, in turn, limit its clinical efficacy. We hypothesized that the addition of a hydrophobic moiety to this molecule would help overcome these limitations and improve its bioavailability in the bloodstream. Therefore, we designed a stable, covalently linked lipid–drug conjugate of isoniazid with a short lipid chain of stearoyl chloride. Further, lipid–drug conjugate nanoparticles were synthesized from the bulk lipid–drug conjugate by a cold high-pressure homogenization method enabled by the optimized use of aqueous surfactants. The nanoparticle formulation was characterized systematically using in vitro physicochemical analytical methods, including atomic force microscopy, transmission electron microscopy, differential scanning calorimetry, X-ray diffraction, attenuated total reflectance, particle size, ζ-potential, and drug release studies, and the mechanism of drug release kinetics. These investigations revealed that the lipid–drug conjugate nanoparticles were loaded with an appreciable amount of isoniazid conjugate (92.73 ± 6.31% w/w). The prepared lipid–drug conjugate nanoparticles displayed a uniform shape with a smooth surface having a particle size of 124.60 ± 5.56 nm. In vitro drug release studies showed sustained release up to 72 h in a phosphate-buffered solution at pH 7.4. The release profile fitted to various known models of release kinetics revealed that the Higuchi model of diffusion kinetics was the best-fitting model (R2 = 0.9929). In addition, confocal studies showed efficient uptake of lipid–drug conjugate nanoparticles by THP-1 macrophages presumably because of increased lipophilicity and anionic surface charge. This was followed by progressive intracellular trafficking into endosomal and lysosomal vesicles and colocalization with intravesicular compartmental proteins associated with mycobacterium tuberculosis pathogenesis, including CD63, LAMP-2, EEA1, and Rab11. The developed lipid–drug conjugate nanoparticles, therefore, displayed significant ability to improve the intracellular delivery of a highly water-soluble drug such as isoniazid.

Inhalable Spray-Dried Chondroitin Sulphate Microparticles: Effect of Different Solvents on Particle Properties and Drug Activity.

Spray-drying stands as one of the most used techniques to produce inhalable microparticles, but several parameters from both the process and the used materials affect the properties of the resulting microparticles. In this work, we describe the production of drug-loaded chondroitin sulphate microparticles by spray-drying, testing the effect of using different solvents during the process. Full characterisation of the polymer and of the aerodynamic properties of the obtained microparticles are provided envisaging an application in inhalable tuberculosis therapy. The spray-dried microparticles successfully associated two first-line antitubercular drugs (isoniazid and rifabutin) with satisfactory production yield (up to 85%) and drug association efficiency (60%–95%). Ethanol and HCl were tested as co-solvents to aid the solubilisation of rifabutin and microparticles produced with the former generally revealed the best features, presenting a better ability to sustainably release rifabutin. Moreover, these presented aerodynamic properties compatible with deep lung deposition, with an aerodynamic diameter around 4 μm and fine particle fraction of approximately 44%. Finally, it was further demonstrated that the antitubercular activity of the drugs remained unchanged after encapsulation independently of the used solvent.

Adverse drug reaction prevalence and mechanisms of action of first-line anti-tubercular drugs

PurposeUnderstanding the appearance of anti-tubercular drug-related adverse drug reactions (ADRs) in patients receiving tuberculosis (TB) treatment is important, and may be related to morbidity and mortality if not recognized early. Here, we aimed to characterize the mechanisms underlying adverse drug reactions due to combination anti-tuberculosis therapy of the Revised National Tuberculosis Control Program (RNTCP). MethodsThis was a prospective observational study conducted in 9 DOTS centers of New Delhi, India. All enrolled TB patients receiving first-line tuberculosis treatment as per RNTCP guidelines were monitored for ADRs. All ADRs that appeared during the treatment were recorded and analyzed. ResultsThe study included 1011 TB patients on anti-TB treatment under DOTS. According to Naranjo’s probability scale, of a total 351 (34.72%) reported adverse events, 102 (10.09%) were definite, 59 (5.83%) probable, 123 (12.17%) possible, and 67 (6.63%) doubtful. On the Hartwig severity scale, of the 351 adverse drug events, 225 (22.26%) were mild, 105 (10.38%) were moderate, and 21 (2.08%) were severe. Out of 102 reported adverse drug reactions, 81 (79.41%) were moderate and 21 (20.59%), while 65.28% did not experience any ADRs. ConclusionsDirectly Observed Treatment (DOT) is effective and safe compared to daily treatment regimens. Patients receiving DOTS therapy needed close monitoring for adverse events. Therefore, a pharmacovigilance program should be added at the National level to accesses the adverse event incidence.

CYSTIC TUBERCULOSIS OF TALUS IN A CHILD: A CASE REPORT

Tuberculosis of the talus is an unusual presentation of musculoskeletal tuberculosis. It is a rare manifestation of extra-pulmonary tuberculosis (EPTB) and accounts for around 0.1 to 0.3% of total EPTB. Its indolent nature often leads to missed or delayed diagnosis. Thus, prompt diagnosis is of utmost importance as diagnostic and therapeutic delay can worsen the prognosis. We are reporting a case of an 8-year-old boy with tuberculosis of the isolated right Talus with discharging sinus. The X-ray showed a cystic form of tuberculosis. He was treated with first-line antitubercular drugs. The child responded to the chemotherapy and by the end of the12-month course, he was asymptomatic. Thus, early diagnosis and therapy are crucial for good results.

Determining the unbinding events and conserved motions associated with the pyrazinamide release due to resistance mutations of Mycobacterium tuberculosis pyrazinamidase

Pyrazinamide (PZA) is the only first-line antitubercular drug active against latent Mycobacterium tuberculosis (Mtb). It is activated to pyrazinoic acid by the pncA-encoded pyrazinamidase enzyme (PZase). Despite the emergence of PZA drug resistance, the underlying mechanisms of resistance remain unclear. This study investigated part of these mechanisms by modelling a PZA-bound wild type and 82 mutant PZase structures before applying molecular dynamics (MD) with an accurate Fe2+ cofactor coordination geometry. After observing nanosecond-scale PZA unbinding from several PZase mutants, an algorithm was developed to systematically detect ligand release via centre of mass distances (COM) and ligand average speed calculations, before applying the statistically guided network analysis (SGNA) method to investigate conserved protein motions associated with ligand unbinding. Ligand and cofactor perspectives were also investigated. A conserved pair of lid-destabilising motions was found. These consisted of (1) antiparallel lid and side flap motions; (2) the contractions of a flanking region within the same flap and residue 74 towards the core. Mutations affecting the hinge residues (H51 and H71), nearby residues or L19 were found to destabilise the lid. Additionally, other metal binding site (MBS) mutations delocalised the Fe2+ cofactor, also facilitating lid opening. In the early stages of unbinding, a wider variety of PZA poses were observed, suggesting multiple exit pathways. These findings provide insights into the late events preceding PZA unbinding, which we found to occur in some resistant PZase mutants. Further, the algorithm developed here to identify unbinding events coupled with SGNA can be applicable to other similar problems.

Multidrug resistance in tubercular mediastinal adenopathy diagnosed by endobronchial ultrasound-transbronchial needle aspiration.

Background:Drug resistance in tuberculosis (TB) is a major public health problem. It is easy to assess for drug resistance in pulmonary samples, but the resistance pattern of TB in the mediastinal nodes has not been studied. The aim of this study is to assess the incidence of multidrug resistance in tubercular mediastinal adenopathy with the help of endobronchial ultrasound (EBUS)-guided transbronchial needle aspiration.Materials and Methods:This was a prospective study at a tertiary care teaching hospital in New Delhi where 102 patients with positive mycobacterial cultures from mediastinal lymph node aspirates taken with the help of EBUS were enrolled over 24 months and their drug sensitivity to the first-line antitubercular drugs analyzed.Results:There were 30 cases of drug resistance of 102 culture-positive cases. Of them, 8 patients had multidrug resistant TB (MDR-TB), 16 cases had only single drug resistance, and the remaining 6 cases had more than one drug resistance pattern but not MDR. In our study, the overall incidence of MDR-TB is 7.8% (8/102), although the incidence of MDR-TB in new and re-treatment cases is 2.2% (2/89) and 46.1% (6/13), respectively.Conclusion:Such a high percentage of drug-resistant patients is common in tertiary care hospitals; however, similar percentages may be found in other settings as well. Therefore, all efforts should be made to take samples for Mycobacterium tuberculosis culture from the involved nodes before commencing therapy to avoid treatment failures.

The bioisosteric modification of pyrazinamide derivatives led to potent antitubercular agents: Synthesis via click approach and molecular docking of pyrazine-1,2,3-triazoles

Tuberculosis remains as a major public health risk which causes the highest mortality rate globally and an improved regimen is required to treat the drug-resistant strains. Pyrazinamide is a first-line antitubercular drug used in combination therapy with other anti-TB drugs. Herein, we describe the modification of pyrazinamide structure using bioisosterism and rational approaches by incorporating the 1,2,3-triazole moiety. Three sets of pyrazine-1,2,3-triazoles (3a-o, 5a-o and 9a-l) are designed, synthesized and evaluated for their in vitro inhibitory potency against mycobacterium tuberculosis H37Rv. The pyrazine-1,2,3-triazoles synthesized through the bioisosteric modification displayed improved activity as compared to rationally modified pyrazine-1,2,3-triazoles. Among 42 title compounds, seven derivatives demonstrated significant anti-tubercular activity with the MIC of 1.56 μg/mL, which are two-fold more potent than the parent compound pyrazinamide. Further, the synthesized pyrazinamide analogs demonstrated moderate inhibition activity against several bacterial strains and possessed an acceptable in vitro cytotoxicity profile as well. Additionally, the activity profile of pyrazine-1,2,3-triazoles was validated by performing the molecular docking studies against the Inh A enzyme. Furthermore, in silico ADME prediction revealed good oral bioavailability for the potent molecules.