@article { ISI:000257626900005, title = {Bactericidal activity of 2-nitroimidazole against the active replicating stage of mycobacterium bovis BCG and mycobacterium tuberculosis with intracellular efficacy in THP-1 macrophages}, journal = {International Journal of Antimicrobial Agents}, volume = {32}, number = {1}, year = {2008}, month = {JUL}, pages = {40-45}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

This study evaluated the antituberculous potential of 2-nitroimidazole under in vitro conditions. Minimal bactericidal concentrations of the compound against actively replicating Mycobacterium bovis BCG and Mycobacterium tuberculosis H37Ra were found to be 0.226 mu g/mL and 0.556 mu g/mL in enriched and minimal medium, respectively. Minimal inhibitory concentrations were \> 100 times lower than reported antituberculous nitroimidazoles such as nitrofurantoin and furaltadone, indicating the greater potential of 2-nitroimidazole. No discernible effect of 2-nitroimidazole was seen on saprophytic Mycobacterium smegmatis and the representative bacterial strain Escherichia coli DH5 alpha, indicating the specificity of the molecule against tuberculous mycobacteria. The compound was also found to be effective against M. tuberculosis in the intracellular environment of the human monocytic cell line THP-1, with a reduction in viability of bacilli by 2.5 log after 144 h of incubation at a concentration of 0.113 mu g/mL. A five-fold higher concentration (0.565 mu g/mL) of 2-nitroimidazole sterilised the macrophages of intracellular pathogens within 192 h, without affecting the host. However, 2-nitroimidazole was unable to affect significantly the viability of dormant non-replicating bacilli of M. bovis BCG and M. tuberculosis in Wayne{\textquoteright}s in vitro model. Overall, the results indicate that 2-nitroimidazole is a potent antituberculous agent active against the organism{\textquoteright}s active replicating stage, with promising intracellular efficacy as well. (c) 2008 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.

}, keywords = {2-nitroimidazole, antimycobacterial agents, nitroimidazoles, THP-1 macrophage, tuberculosis}, issn = {0924-8579}, doi = {10.1016/j.ijantimicag.2008.02.022}, author = {Khan, Arshad and Sarkar, Sampa and Sarkar, Dhiman} } @article { ISI:000255300600009, title = {Simple whole cell based high throughput screening protocol using Mycobacterium bovis BCG for inhibitors against dormant and active tubercle bacilli}, journal = {Journal of Microbiological Methods}, volume = {73}, number = {1}, year = {2008}, month = {APR}, pages = {62-68}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

This study aimed at developing a whole cell based high throughput screening protocol to identify inhibitors against both active and dormant tubercle bacilli. A respiratory type of nitrate reductase (NarGHJI), which was induced during dormancy, could reflect the viability of dormant bacilli of Mycobacterium bovis BCG in microplate adopted model of in vitro dormancy. Correlation between reduction in viability and nitrate reductase activity was seen clearly when dormant stage inhibitor metronidazole and itaconic anhydride were applied in this in vitro microplate model. Active replicating stage could also be monitored in the same assay by measuring the A(620) of the culture. MIC values of 0.08, 0.075, 0.3 and 3.0 mu g/ml, determined through monitoring A(620) in this assay for rifampin, isoniazid, streptomycin and ethambutol respectively, were well in agreement with previously reported by BACTEC and Bio-Siv assays. S/N ratio and Z{\textquoteright} factor for the assay were 8.5 and 0.81 respectively which indicated the robustness of the protocol. Altogether the assay provides an easy, inexpensive, rapid, robust and high content screening too] to search novel antitubercular molecules against both active and dormant bacilli. (C) 2008 Elsevier B.V. All rights reserved.

}, keywords = {high throughput screening, tuberculosis, Wayne{\textquoteright}s dormancy model, whole cell based assay}, issn = {0167-7012}, doi = {10.1016/j.mimet.2008.01.015}, author = {Khan, Arshad and Sarkar, Dhiman} } @article { ISI:000360705500008, title = {Chemical and biological metal nanoparticles as antimycobacterial agents: a comparative study}, journal = {International Journal of Antimicrobial Agents}, volume = {46}, number = {2}, year = {2015}, month = {AUG}, pages = {183-188}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Resistance among mycobacteria leading to multidrug-resistant and extensively drug-resistant tuberculosis is a major threat. However, nanotechnology has provided new insights in drug delivery and medicine development. This is the first comparative report to determine the activity of chemically and biologically synthesised silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) against mycobacteria. Screening data revealed the high mycobactericidal efficiency of AgNPs, with minimum inhibitory concentrations (MICs) of \<3 mu g/mL, whereas no such activity was exhibited by AuNPs at concentrations up to 100 mu g/mL. Moreover, in vitro and ex vivo THP-1 infection model assays showed greater efficacy of chemical AgNPs compared with biogenic AgNPs to inhibit active and dormant stage mycobacterial growth. Up to 40\% cytotoxicity against human cell lines was observed at a AgNP concentration of 10 x MIC (30 mu g/mL) after 48 h. AgNPs were shown to have more specificity towards mycobacteria than towards other Gram-negative and Gram-positive pathogenic bacteria. The selectivity index was found to be in the range of 11-23, indicating the potential of these nanoparticles for use in developing new therapeutics for tuberculosis. (C) 2015 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.

}, keywords = {Antibiotic resistance, Antimycobacterial agent, Cytotoxicity, Mycobacteria, Nanoparticles, tuberculosis}, issn = {0924-8579}, doi = {10.1016/j.ijantimicag.2015.03.014}, author = {Singh, Richa and Nawale, Laxman U. and Arkile, Manisha A. and Shedbalkar, Utkarsha U. and Wadhwani, Sweety A. and Sarkar, Dhiman and Chopade, Balu Ananda} } @article { ISI:000356251500001, title = {Qualitative and quantitative proteomic analysis of vitamin C induced changes in mycobacterium smegmatis}, journal = {Frontiers in Microbiology}, volume = {6}, year = {2015}, month = {MAY}, pages = {Article Number: 451}, publisher = {FRONTIERS RESEARCH FOUNDATION}, address = {PO BOX 110, LAUSANNE, 1015, SWITZERLAND}, abstract = {

Vitamin C is a critical dietary nutrient in human which has a wide range of regulatory effects on gene expression and physiology of Mycobacterium tuberculosis that leads to a dormant drug-tolerant phenotype. In the presence of iron, vitamin C shows a high bactericidal activity even in the drug resistant phenotype of M. tuberculosis. The regulatory mechanisms underlying vitamin C induced adaptations are largely unknown due to lack of functional genomics data in this field. In this study, we attempt to characterize the direct effect of vitamin C treatment on the physiology of actively growing Mycobacterium smegmatis. The study chose M. smegmatis as it is a fast-growing bacterium and a non-pathogenic model system which shares many physiological features with the pathogenic M. tuberculosis including dormancy and its regulation. The proteomic adaptation of M. smegmatis on vitamin C treatment demonstrates the important changes in cellular and metabolic process such as reversal of tricarboxylic acid cycle, decrease in ATP synthesis, decrease in iron acquisition and storage, and induction of dormancy regulators WhiB3, PhoP, and Lsr2.

}, keywords = {dormancy, Mycobacterium smegmatis, proteomics, tuberculosis, vitamin C}, issn = {1664-302X}, doi = {10.3389/fmicb.2015.00451}, author = {Mishra, Abhishek and Sarkar, Dhiman} } @article { ISI:000375559600001, title = {Phytogenic silver, gold, and bimetallic nanoparticles as novel antitubercular agents}, journal = {International Journal of Nanomedicine}, volume = {11}, year = {2016}, month = {MAY}, pages = {1889{\textemdash}1897}, publisher = {DOVE MEDICAL PRESS LTD}, address = {PO BOX 300-008, ALBANY, AUCKLAND 0752, NEW ZEALAND}, abstract = {

Purpose: Multi- and extensively drug-resistant tuberculosis (TB) is a global threat to human health. It requires immediate action to seek new antitubercular compounds and devise alternate strategies. Nanomaterials, in the present scenario, have opened new avenues in medicine, diagnosis, and therapeutics. In view of this, the current study aims to determine the efficacy of phytogenic metal nanoparticles to inhibit mycobacteria. Methods: Silver (AgNPs), gold (AuNPs), and gold-silver bimetallic (Au-AgNPs) nanoparticles synthesized from medicinal plants, such as Barleria prionitis, Plumbago zeylanica, and Syzygium cumini, were tested against Mycobacterium tuberculosis and M. bovis BCG. In vitro and ex vivo macrophage infection model assays were designed to determine minimum inhibitory concentration (MIC) and half maximal inhibitory concentration of nanoparticles. Microscopic analyses were carried out to demonstrate intracellular uptake of nanoparticles in macrophages. Besides this, biocompatibility, specificity, and selectivity of nanoparticles were also established with respect to human cell lines. Results: Au-AgNPs exhibited highest antitubercular activity, with MIC of \<2.56 mu g/mL, followed by AgNPs. AuNPs did not show such activity at concentrations of up to 100 mu g/mL. In vitro and ex vivo macrophage infection model assays revealed the inhibition of both active and dormant stage mycobacteria on exposure to Au-AgNPs. These nanoparticles were capable of entering macrophage cells and exhibited up to 45\% cytotoxicity at 30 mu g/mL (ten times MIC concentration) after 48 hours. Among these, Au-AgNPs synthesized from S. cumini were found to be more specific toward mycobacteria, with their selectivity index in the range of 94-108. Conclusion: This is the first study to report the antimycobacterial activity of AuNPs, AgNPs, and Au-AgNPs synthesized from medicinal plants. Among these, Au-AgNPs from S. cumini showed profound efficiency, specificity, and selectivity to kill mycobacteria. These should be investigated further to develop novel TB nanoantibiotics.

}, keywords = {Antimycobacterial agent, Cytotoxicity, drug resistance, Mycobacteria, Nanoparticles, tuberculosis}, issn = {1178-2013}, doi = {10.2147/IJN.S102488}, author = {Singh, Richa and Nawale, Laxman and Arkile, Manisha A. and Wadhwani, Sweety and Shedbalkar, Utkarsha and Chopade, Snehal and Sarkar, Dhiman and Chopade, Balu Ananda} } @article { ISI:000373739700025, title = {Synthesis and docking studies of pyrazine-thiazolidinone hybrid scaffold targeting dormant tuberculosis}, journal = {Bioorganic \& Medicinal Chemistry Letters}, volume = {26}, number = {9}, year = {2016}, month = {MAY}, pages = {2224-2228}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

The persistence of Mycobacterium tuberculosis (MTB) in dormant stage assists the pathogen to develop resistance against current antimycobactrial drugs. To address this issue, we report herein the synthesis of N-(4-oxo-2 substituted thiazolidin-3yl) pyrazine-2-carbohydrazide derivatives designed by following the molecular hybridization approach using pyrazine and thiazolidenone scaffolds. The compounds were evaluated against MTB H37Ra and Mycobacterium bovis BCG in dormancy model. Most of the compounds had IC50 values in 0.3-1 mu g/ml range. The active compounds were further tested for anti-proliferative activity against THP-1, Panc-1, A549, and MCF-7 cell lines using MTT assay and exhibited no significant cytotoxicity. We also report molecular docking studies using active analogs and MTB Decaprenylphosphoryl-beta-D-ribose-2{\textquoteright}-epimerase (DprE1) to rationalize the biological activity and to provide an insight into the probable mechanism of action and binding mode of hybridized structures. The results obtained validate the use of molecular hybridization approach and also suggest that reported compounds can provide a novel pharmacophore to synthesize lead compounds against dormat MTB. (C) 2016 Elsevier Ltd. All rights reserved.

}, keywords = {docking, Dormant, Hybrid design, Pyrazine, Thiazolidenone, tuberculosis}, issn = {0960-894X}, doi = {10.1016/j.bmcl.2016.03.055}, author = {Chitre, T. S. and Asgaonkar, K. D. and Miniyar, P. B. and Dharme, A. B. and Arkile, Manisha A. and Yeware, A. and Sarkar, Dhiman and Khedkar, Vijay M. and Jha, Prakash C.} } @article {46985, title = {Pharmacophore modeling of pretomanid (PA-824) derivatives for antitubercular potency against replicating and non-replicating Mycobacterium tuberculosis}, journal = {Journal of Biomolecular Structure \& Dynamics}, volume = {39}, year = {2021}, month = {FEB}, pages = {889-900}, type = {Article}, abstract = {

Pretomanid (PA-824) is the recently (2019) approved drug for the treatment of extensively drug-resistant (XDR) TB and the multidrug-resistant (MDR) TB by US FDA. The experimental data of antitubercular activity of 543 pretomanid derivatives (total 6 datasets) against replicating (active) and non-replicating (dormant) forms of Mycobacterium tuberculosis (strain H37Rv) are available in the literature. Such vast experimental data of pretomanid derivatives against both of these endpoints, and recent approval of pretomanid molecule as a drug encouraged us to utilize this existing experimental information for the development of the 3D-pharmacophore models. The developed model (Hypo-1, MABA) showed the three physicochemical features namely, the oxygen atom of nitro group (HBA_1), fused pyran ring of imidazopyran heterocycle (HYAl_2) and the 4-fluorophenyl moiety (HYAr_3) are crucial for the antitubercular activity against replicating M. tb. Subsequently, the pharmacophore model (Hypo-1, LORA) developed against the non-replicating form of M. tb also showed the contribution of three physicochemical features namely, the 4-tri-fluoromethyl group (HYAl_2) and both the phenyl groups (HYAr_3, HYAr_4) of biaryl moiety in increasing the antitubercular activity. Both the pharmacophoric classifier models showed the classification accuracies of 82.98 and 74.42\% for the training set compounds, and 63.91 and 61.60\% for the test set compounds respectively, for labelling the compounds into higher and lower active classes. Both the models were also found to be retaining the higher active compounds in top 1.00\% of the total number of compounds (decoys and actives), after performing the decoy set screening. Communicated by Ramaswamy H. Sarma

}, keywords = {LORA assay, MABA assay, Mycobacterium tuberculosis, non-replicating M, pharmacophore modeling, pretomanid derivatives, replicating M, tuberculosis, virtual screening}, issn = {0739-1102}, doi = {10.1080/07391102.2020.1719205, Early Access Date = JAN 2020}, author = {Aher, Rahul Balasaheb and Sarkar, Dhiman} } @article {47820, title = {Probes and techniques used in active and the hypoxia-based dormant state of an antitubercular drug screening assay}, journal = {Medicine in Drug Discovery}, volume = {13}, year = {2022}, month = {MAR}, pages = {100115}, type = {Article}, abstract = {Current antitubercular drug therapy requires more than six months and is unable to kill latent or dormant forms of tuberculosis. Thus, it is a need of new drug therapy to fight against dormant tuberculosis. However, the major obstacle in the development of novel drugs for dormant tuberculosis is the lack of relevant screening systems and using reliable probes to measure growth inhibition. Until now, several probes used in active state assays are significantly determining the inhibitory effect against the active state of mycobacteria. The dormant condition assays are based on hypoxia-derived dormancy which include resazurin reduction assay, nitrite reductase assay, XTT reduction menadione assay and low oxygen recovery assay. Major probes used in those assays are colorimetric/fluorescent dyes, enzymatic activity, and reporter genes include luciferase and fluorescent proteins. Although these dormant assays are based on hypoxia-induced features and difficult to maintain for a longer duration. Also, they further complicated by growth detection and pursuit of high throughput screening criteria. Here we reviewed complications of probes and assay techniques used for anti-dormant drug screening programs of tuberculosis. This will provide the knowledge to design better alternative drug screening method for the anti-dormant form of tuberculosis.}, keywords = {Active and dormant states, and, Drug screening assay, Probes, tuberculosis}, issn = {2590-0986}, doi = {10.1016/j.medidd.2021.100115}, author = {Yeware, Amar and Akhtar, Shamim and Sarkar, Dhiman} }