Potent Antimycobacterial Activity Research Articles

Confronting Tuberculosis: A Synthetic Quinoline-Isonicotinic Acid Hydrazide Hybrid Compound as a Potent Lead Molecule Against Mycobacterium tuberculosis.

The current tuberculosis (TB) treatment is challenged by a complex first-line treatment for drug-sensitive (DS) TB. Additionally, the prevalence of multidrug (MDR)- and extensively drug (XDR)-resistant TB necessitates the search for new drug prototypes. We synthesized and screened 30 hybrid compounds containing aminopyridine and 2-chloro-3-formyl quinoline to arrive at a compound with potent antimycobacterial activity, UH-NIP-16. Subsequently, antimycobacterial activity against DS and MDR Mycobacterium tuberculosis (M.tb) strains were performed. It demonstrated an MIC50 value of 1.86 ± 0.21 μM for laboratory pathogenic M.tb strain H37Rv and 3.045 ± 0.813 μM for a clinical M.tb strain CDC1551. UH-NIP-16 also decreased the MIC50 values of streptomycin, isoniazid, ethambutol, and bedaquiline to about 45, 55, 68, and 76%, respectively, when used in combination, potentiating their activities. The molecule was active against a clinical MDR M.tb strain. Cytotoxicity on PBMCs from healthy donors and on human cell lines was found to be negligible. Further, blind docking of UH-NIP-16 using Auto Dock Vina and MGL tools onto diverse M.tb proteins showed high binding affinities with multiple M.tb proteins, the top five targets being metabolically critical proteins CelA1, DevS, MmaA4, lysine acetyltransferase, and immunity factor for tuberculosis necrotizing toxin. These bindings were confirmed by fluorescence spectroscopy using a representative protein, MmaA4. Envisaging that a pathogen will have a lower probability of developing resistance to a hybrid molecule with multiple targets, we propose that UH-NIP-16 can be further developed as a lead molecule with the bacteriostatic potential against M.tb, both alone and in combination with first-line drugs.

Synthesis, in vitro and in silico screening of novel ferrocenyl substituted cyclohexenone and indazole derivatives as effective antimycobacterial agents

In response to the escalating threat of mycobacterial infections, including extensively drug-resistant tuberculosis (XDR) and multidrug-resistant tuberculosis (MDR), we synthesized novel ferrocene incorporating cyclohexenone and indazole derivatives. The compounds were synthesized via multistep reaction approach starting from chalcone precursors and evaluated against Mycobacterium fortuitum. The MIC and MBC values were calculated by following CLSI guidelines, with a focus on their ability to inhibit bacterial growth and disrupt biofilm formation. All the test compounds showed potent in vitro antimycobacterial activity against M. fortuitum. The MIC values range from 3.907 µg/mL to 500 µg/mL, whereas the MBC values range from 15.625 µg/mL to >500 µg/mL. Among the synthesized compounds, compound 3b exhibited potent antimycobacterial activity compared with standard drug Amikacin used to treat multidrug-resistant tuberculosis. 3b demonstrated significant inhibition of bacterial growth and showed the capacity to effectively suppress biofilm formation and disrupt pre-existing biofilms. This molecule also displayed favourable ADMET profile and good oral bioavailability, besides showing potential interactions with the target enzyme as revealed by docking studies and validated by enzyme assay. Collectively, these studies position 3b as a potential lead molecule that could be further optimized to develop ferrocene incorporating indazole based antimycobacterial agents.

Redefining Peptide 14D: Substitutional Analysis for Accelerated TB Diagnosis and Enhanced Activity against Mycobacterium tuberculosis.

Tuberculosis (TB) caused by Mycobacterium tuberculosis remains a predominant cause of mortality, especially in low- and middle-income nations. Recently, antimicrobial peptides have been discovered that at low concentrations could stimulate the growth of M. tuberculosis (hormetic response). In this study, such a peptide was used to investigate the effects on the time to positivity (TTP). A systematic substitution analysis of peptide 14D was synthesized using Spot synthesis technology, resulting in 171 novel peptides. Our findings revealed a spectrum of interactions, with some peptides accelerating M. tuberculosis growth, potentially aiding in faster diagnostics, while others exhibited inhibitory effects. Notably, peptide NH2-wkivfiwrr-CONH2 significantly reduced the TTP by 25 h compared to the wild-type peptide 14D, highlighting its potential in improving TB diagnostics by culture. Several peptides demonstrated potent antimycobacterial activity, with a minimum inhibitory concentration (MIC) of 20 µg/mL against H37Rv and a multidrug-resistant M. tuberculosis strain. Additionally, for two peptides, a strongly diminished formation of cord-like structures was observed, which is indicative of reduced virulence and transmission potential. This study underscores the multifaceted roles of antimicrobial peptides in TB management, from enhancing diagnostic efficiency to offering therapeutic avenues against M. tuberculosis.

Screening for Antimycobacterial Activity of Actinomycetes Collected in Vietnam – Isolation and Activity of Metabolites from Streptomyces alboniger (A121)

Objective Actinomycetes have been known to be the great natural sources to explore antibiotics for the treatment of tuberculosis (TB). The isolation of actinomycetes from the samples in Vietnam followed by the screening of their antimycobacterial activity was performed in this study. The metabolites isolated from the most active strain were further evaluated for their antimycobacterial, antimicrobial and cytotoxic activity. Methods Actinomycetes were growth in culture media, isolated and identified by colony, spore chain morphology and 16S rRNA gene sequencing. Agar diffusion assay was used for the screening of the isolated strains against Mycobacterium smegmatis, a safety surrogate for Mycobacterium tuberculosis. The metabolites produced from the most active strain were investigated by actinomycete fermentation, extraction and isolation from biomass and cultures. The structures of the isolated compound were elucidated by spectral data and comparison with the reported literatures. Results 181 strains were isolated from nine regions along the north to central Vietnam. The five most active strains against Mycobacterium smegmatis were detected. Following the bioassay-guided result, the strain A121 ( Streptomyces alboniger) was selected for further isolation of the bioactive metabolites. As a result, obscurolide B2β (1) and chartreusin (2) were obtained and evaluated for their antimycobacterial activity against M. smegmatis. Compound 2 displayed potential antimycobacterial activity, antimicrobial effect against the Gram positive bacteria Staphylococcus aureus, Bacillus subtilis, Lactobacillus fermentum and cytotoxicity against four cancer cell lines KB, HepG-2, Lu-1 and MCF-7. Conclusions Five strains possessing potential antimycobacterial activity were identified from the samples collected in Vietnam. Two compounds including obscurolide B2β (1) and chartreusin (2) were isolated from the most active strain A121 ( Streptomyces alboniger). This is the first time these compounds have been isolated from this strain. Chartreusin (2) exhibited notable antimycobacterial, antimicrobial and cytotoxic activity, making its worthy attention for further drug development, particularly for antituberculosis therapeutic agents.

New Benzotriazole Derivatives: Synthesis, Biological Assessment, In vivo Oral Toxicity Analysis, Docking Studies, Molecular Dynamics, and ADME Profiling

A new series of phenyl-2-(perchloro-1H-benzo[d] [1,2,3]triazol-1-yl)- acetamide derivatives (3a-k) was synthesized and assessed for antimycobacterial, antibacterial, and antifungal effects. Compound 3c displayed potent antimycobacterial, antibacterial, and antifungal activity, comparable to the standard drug. Highly active compounds were analyzed for their binding mode in the active site using the cocrystallized structure of mycobacterium tuberculosis (PDB ID 2X22) and glucosamine-6-phosphate synthase (PDB ID 2VF5), followed by molecular dynamics. Finally, in vivo oral toxicity study confirmed the non-toxic nature of the compound 3c.. KEYWORDS :Antifungal, Antimicrobial, Antimycobacterial, Molecular docking, Molecular dynamics

Synthesis and screening of clerodane diterpene analogues from 16 hydroxycleroda 3,13(14)-Z-diene 15,16-olide for potential anti-mycobacterial activity

In recent years, clerodane diterpenes, a class of bioactive compounds, have come into the spotlight due to their amazing bioactivities. Three novel clerodane diterpene analogues were obtained by synthesising 16-hydroxycleroda-3,13(14)-Z-diene-15,16-olide (Lactone) with primary amines. Anti-tubercular activity was determined using Microplate Alamar Blue Assay. Among all the synthesised compounds from methanolic extract of seeds, results clearly showed that compounds 3 and 5 have significant anti TB activity with an MIC of 1.56 µg/ml against the Mycobacterium tuberculosis MTB H37Rv bacilli strain than the gold standard drugs pyrazinamide (3.13 µg/ml), ciprofloxacin (3.13 µg/ml), streptomycin (6.25 µg/ml) and rifampicin (6.25 µg/ml). Compound 5 exhibited significant antibacterial activity with zone of inhibition of 10.8 mm with Gram + ve and 7.95 mm with Gram -ve bacteria at a conc of 50 µg/ml respectively. In the current investigation, three novel heterocycles (compounds 3-5) of the diterpenoid were prepared, in high yield, using one-pot, efficient approach.

In-silico and in-vitro assessments of some fabaceae, rhamnaceae, apocynaceae, and anacardiaceae species against Mycobacterium tuberculosis H37Rv and triple-negative breast cancer cells

Medicinal plants play a huge role in the treatment of various diseases in the Limpopo province (South Africa). Traditionally, concoctions used for treating tuberculosis and cancer are sometimes prepared from plant parts naturally occurring in the region, these include (but not limited to) Schotia brachypetala, Rauvolfia caffra, Schinus molle, Ziziphus mucronate, and Senna petersiana. In this study, the aim was to evaluate the potential antimycobacterial activity of the five medicinal plants against Mycobacterium smegmatis mc2155, Mycobacterium aurum A + , and Mycobacterium tuberculosis H37Rv, and cytotoxic activity against MDA-MB 231 triple-negative breast cancer cells. Phytochemical constituents present in R. caffra and S. molle were tentatively identified by LC-QTOF-MS/MS as these extracts showed antimycobacterial and cytotoxic activity. A rigorous Virtual Screening Workflow (VSW) of the tentatively identified phytocompounds was then employed to identify potential inhibitor/s of M. tuberculosis pantothenate kinase (PanK). Molecular dynamics simulations and post-MM-GBSA free energy calculations were used to determine the potential mode of action and selectivity of selected phytocompounds. The results showed that plant crude extracts generally exhibited poor antimycobacterial activity, except for R. caffra and S. molle which exhibited average efficacy against M. tuberculosis H37Rv with minimum inhibitory concentrations between 0.25–0.125 mg/mL. Only one compound with a favourable ADME profile, namely, norajmaline was returned from the VSW. Norajmaline exhibited a docking score of –7.47 kcal/mol, while, pre-MM-GBSA calculation revealed binding free energy to be –37.64 kcal/mol. All plant extracts exhibited a 50% inhibitory concentration (IC50) of < 30 μg/mL against MDA-MB 231 cells. Flow cytometry analysis of treated MDA-MB 231 cells showed that the dichloromethane extracts from S. petersiana, Z. mucronate, and ethyl acetate extracts from R. caffra and S. molle induced higher levels of apoptosis than cisplatin. It was concluded that norajmaline could emerge as a potential antimycobacterial lead compound. Validation of the antimycobacterial activity of norajmaline will need to be performed in vitro and in vivo before chemical modifications to enhance potency and efficacy are done. S. petersiana, Z. mucronate, R.caffra and S. molle possess strong potential as key contributors in developing new and effective treatments for triple-negative breast cancer in light of the urgent requirement for innovative therapeutic solutions.

Membrane-active and DNA binding related double-action antimycobacterial mechanism of antimicrobial peptide W3R6 and its synthetic analogs

The emergence of multidrug- or extremely drug-resistant M. tuberculosis strains has made very few drugs available for current tuberculosis treatment. Antimicrobial peptides can be employed as a promising alternative strategy for TB treatment. Here, we designed and synthesized a series of peptide sequences based on the structure-activity relationships of natural sequences of antimicrobial peptides. The peptide W3R6 and its analogs were screened and found to have potent antimycobacterial activity against M. smegmatis, and no hemolytic activity against human erythrocytes. The evidence from the mechanism of action study indicated that W3R6 and its analogs can interact with the mycobacterial membrane in a lytic manner and form pores on the outer membrane of M. smegmatis. Significant colocalization of D-W3R6 with mycobacterial DNA was observed by confocal laser scanning microscopy and DNA retardation assays, which suggested that the antimycobacterial mechanism of action of the peptide was associated with the unprotected genomic DNA of M. smegmatis. In general, W3R6 and its analogs act on not only the mycobacterial membrane but also the genomic DNA in the cytoplasm, which makes it difficult for mycobacteria to generate resistance due to the peptides having two targets. In addition, the peptides can effectively eliminate M. smegmatis cells from infected macrophages. Our findings indicated that the antimicrobial peptide W3R6 could be a novel lead compound to overcome the threat from drug-resistant M. tuberculosis strains in the development of potent AMPs for TB therapeutic applications.

Concentration of contezolid in cerebrospinal fluid and serum in a patient with tuberculous meningoencephalitis: A case report

Central nervous system (CNS) tuberculosis (TB) is a devastating and often life-threatening disease caused by M. tuberculosis. Contezolid, a new oxazolidinone, has demonstrated potent antimycobacterial activity in both in vivo and in vitro studies, with lower toxicity than linezolid. However, the pharmacokinetic datav are still not available for contezolid in the CNS of patients with CNS TB. We report the steady-state concentrations in serum and CSF of a patient receiving contezolid as part of multi-drug treatment for tuberculous meningoencephalitis. At weeks 7 and 11 (7 hours post-dose) after initiation of contezolid therapy, the serum concentration of contezolid was 9.64mg/L and 9.36mg/L, respectively. In CSF, the observed concentration of contezolid was 0.54mg/L and 1.15mg/L. The CSF to serum concentration ratio was 0.056 and 0.123 at week 7 and week 11, respectively. The observed concentrations in CSF were above the minimum inhibitory concentration (MIC) of contezolid against M. tuberculosis and were close to the estimated serum unbound fraction of contezolid (10%), suggesting that the unbound contezolid penetrates well into CSF.

Children deserve simple, short, safe, and effective treatment for rifampicin-resistant tuberculosis

Historically, treatment regimens for rifampicin-resistant tuberculosis were composed of five to seven older, second-line tuberculosis drugs, including injectable agents that resulted in frequent and sometimes permanent adverse effects in some patients, that were given for 18–24 months and were only modestly effective. The development of multiple novel and repurposed tuberculosis drugs has substantially changed the approach to rifampicin-resistant tuberculosis treatment, but children have not benefited equitably. On the basis of emerging results from pivotal trials, in December 2022, WHO recommended a 6-month, once-per-day regimen of bedaquiline, pretomanid, linezolid, and moxifloxacin (BPaLM) as a first-line treatment for individuals older than 14 years with rifampicin-resistant tuberculosis.1WHOWHO consolidated guidelines on tuberculosis. Module 4: treatment—drug-resistant tuberculosis treatment, 2022 update.https://www.who.int/publications/i/item/9789240063129Date: 2022Date accessed: March 5, 2023Google Scholar The inclusion of patients as young as 14 years in these pivotal trials, even though people aged 14–17 years were enrolled in small numbers, allowed WHO to extend their recommendation to this age group, thus avoiding unnecessary delays in access to this much-needed treatment innovation for older adolescents. Most older adolescents and adults aged 18 years or older treated for rifampicin-resistant tuberculosis can now expect to receive an effective, all-oral, once-per-day, four-drug regimen for 6 months. Although extrapolating the efficacy of BPaLM to children aged 13 years or younger with rifampicin-resistant tuberculosis is reasonable, two crucial barriers prevent paediatric access to this regimen. First, although pretomanid was approved by the US Food and Drug Administration in 2019 for use in adults as part of the bedaquiline, pretomanid, and linezolid regimen, paediatric evaluation has been substantially delayed. The pharmacokinetics and safety of a single dose of pretomanid in children and adolescents will be evaluated in the IMPAACT 2034 trial (NCT05586230), which is expected to open in 2023. A subsequent multidose pretomanid paediatric trial will be needed to substantiate these doses and evaluate its safety long term. Pretomanid is thus unlikely to be available for children for several years. Second, although linezolid has potent antimycobacterial activity, its use for 6 months results in frequent adverse effects, including myelosuppression and neuropathies. These adverse events are associated with longer duration and increased exposure.2Conradie F Bagdasaryan TR Borisov S et al.Bedaquiline–pretomanid–linezolid regimens for drug-resistant tuberculosis.N Engl J Med. 2022; 387: 810-823Crossref PubMed Scopus (34) Google Scholar For adults with rifampicin-resistant tuberculosis who typically have severe disease and traditionally poor outcomes, the risk–benefit profile of 6 months of linezolid is favourable. However, for children who tend to have paucibacillary, less severe tuberculosis, and better outcomes, this risk–benefit profile is less acceptable. Shorter linezolid durations would substantially improve this risk–benefit profile, reducing the risk of developing severe anaemia, peripheral neuropathy, and optic neuropathy, which, while rare, might have long-term consequences. Although some experts prescribe shorter, less intense regimens for rifampicin-resistant tuberculosis,3The Sentinel Project on Pediatric Drug-Resistant TuberculosisManagement of multidrug-resistant tuberculosis in children: a field guide.http://sentinel-project.org/2022/03/22/fifth-edition-of-management-of-multidrug-resistant-tuberculosis-in-children-a-field-guide-now-available/Date: 2022Date accessed: May 22, 2023Google Scholar WHO still recommends a 9–11-month treatment regimen for children, composed of a 4–6-month intensive phase with seven drugs (ie, bedaquiline, levofloxacin, clofazimine, pyrazinamide, ethionamide, high-dose isoniazid, and ethambutol) and a 6-month continuation phase with four drugs (ie, levofloxacin, clofazimine, pyrazinamide, and ethambutol).1WHOWHO consolidated guidelines on tuberculosis. Module 4: treatment—drug-resistant tuberculosis treatment, 2022 update.https://www.who.int/publications/i/item/9789240063129Date: 2022Date accessed: March 5, 2023Google Scholar Children respond as well as, or better than, adults to tuberculosis treatment. However, compared with adults, this currently recommended paediatric rifampicin-resistant tuberculosis treatment regimen includes more drugs than BPaLM (ie, seven vs four) and older drugs that are less well tolerated and less likely to be effective for a longer duration than BPaLM (ie, 9–11 months vs 6 months). Currently recommended regimens, although generally safe, are not always well tolerated, with clofazimine-associated skin discoloration and ethionamide-associated nausea and vomiting frequently causing challenges for children and caregivers. Despite the current recommendation that injectable agents be avoided, they are still used in some countries and result in a high risk of permanent sensorineural hearing loss. As children overall respond well to treatment, ensuring the safety and tolerability of regimens, especially to avoid adverse effects with potentially long-term consequences, is imperative. An attractive adaptation of the BPaLM regimen for children would substitute delamanid for pretomanid and shorten the duration of linezolid. Treatment with 6 months of bedaquiline, delamanid, and a fluoroquinolone with 2 months of linezolid could allow children access to an efficacious, all-oral regimen similar to that used in adults. Delamanid and pretomanid are in the same class of drugs (ie, nitroimidazoles) with similar mechanisms of action. At exposures expected with current dosing of both compounds, there appears to be minimal difference in activity in preclinical evaluations.4Mudde SE Upton AM Lenaerts A Bax HI De Steenwinkel JEM Delamanid or pretomanid? A Solomonic judgement!.J Antimicrob Chemother. 2022; 77: 880-902Crossref PubMed Scopus (9) Google Scholar There are no high-quality clinical data directly comparing the two drugs, but a reasonable assumption is that they will have similar activity. This assumption is further supported by preliminary results from the South African BEAT-Tuberculosis trial, which enrolled patients aged 6 years or older and showed that a 6-month delamanid-containing regimen was highly effective,5Conradie F. High rate of successful outcomes treating RR-TB with a delamanid–bedaquiline regimen in BEAT Tuberculosis: an interim analysis. Union World Conference on Lung Health 2022; Nov 8–11, 2022 (LBTB-2074-11).Google Scholar and from the BEAT-India trial.6Padmapriyadarsini C Vohra V Bhatnagar A et al.Bedaquiline, delamanid, linezolid and clofazimine for treatment of pre-extensively drug-resistant tuberculosis.Clin Infect Dis. 2022; 76: e938-e946Crossref PubMed Scopus (6) Google Scholar Delamanid is now recommended by WHO for children of all ages and is available in a dispersible tablet formulation. Furthermore, a shorter duration of linezolid would provide benefit while reducing the risk of adverse effects. The ZeNix trial showed that adults with rifampicin-resistant tuberculosis receiving regimens with 9 weeks of linezolid 600 mg once per day had excellent outcomes with less toxicity than higher doses and longer durations of linezolid.2Conradie F Bagdasaryan TR Borisov S et al.Bedaquiline–pretomanid–linezolid regimens for drug-resistant tuberculosis.N Engl J Med. 2022; 387: 810-823Crossref PubMed Scopus (34) Google Scholar This shorter linezolid duration would result in a more appropriate and favourable risk–benefit profile for most children with rifampicin-resistant tuberculosis. Ease of preparation and administration of any such regimen is also essential to address current poor acceptability in children as a result of complex regimens; these factors can lead to imperfect adherence and increased risk of poor outcomes. Bedaquiline is recommended as thrice-per-week dosing after a 2-week, once-per-day dosing loading phase, and delamanid is recommended as twice-per-day dosing. Once-per-day dosing for both drugs has now been studied in adults and is increasingly used, but also needs to be evaluated in children.7Salinger DH Nedelman JR Mendel C Spigelman M Hermann DJ Daily dosing for bedaquiline in patients with tuberculosis.Antimicrob Agents Chemother. 2019; 63: e00463-e00519Crossref PubMed Scopus (6) Google Scholar, 8von Groote-Bidlingmaier F Patientia R Sanchez E et al.Efficacy and safety of delamanid in combination with an optimised background regimen for treatment of multidrug-resistant tuberculosis: a multicentre, randomised, double-blind, placebo-controlled, parallel group phase 3 trial.Lancet Respir Med. 2019; 7: 249-259Summary Full Text Full Text PDF PubMed Scopus (102) Google Scholar, 9Tanneau L Karlsson MO Rosenkranz SL et al.Assessing prolongation of the corrected QT interval with bedaquiline and delamanid coadministration to predict the cardiac safety of simplified dosing regimens.Clin Pharmacol Ther. 2022; 112: 873-881Crossref PubMed Scopus (3) Google Scholar, 10Mallikaarjun S Chapagain ML Sasaki T et al.Cumulative fraction of response for once- and twice-daily delamanid in patients with pulmonary multidrug-resistant tuberculosis.Antimicrob Agents Chemother. 2020; 65: e01207-e01220Crossref PubMed Scopus (10) Google Scholar Modelling and simulation with existing paediatric bedaquiline and delamanid pharmacokinetic data would enable selection of once-per-day dosing strategies for children for evaluation in a trial. Simple, once-per-day dosing strategies of the overall regimen would improve acceptability and adherence to this regimen. A trial addressing these targeted questions of safety, pharmacokinetics, outcomes, and acceptability of a once-per-day, simple regimen for children with rifampicin-resistant tuberculosis is a crucial priority. Although currently not possible to fully implement the novel BPaLM regimen for children, children receiving longer, more toxic regimens with higher pill burden than adults is unacceptable. A pragmatic alternative is available that should be evaluated immediately. To wait would be unacceptable. ES has received research funding from TB Alliance and Janssen Pharmaceuticals, has received financial compensation from WHO, and is a member of the Data Safety Monitoring Board for the BE-PEOPLE leprosy prevention study. SK has received grants, paid to her institution, from the National Institutes of Health, Unitaid, and CRDF Global and is a Data Safety Monitoring Board member for the DRAMATIC trial. AJG-P has received grants, paid to his institution, from Unitaid and the National Institutes of Health. PH has received research funding, paid to her institution. from TB Alliance and the National Institutes of Health. GH has received financial assistance from the EU (DCI-PANAF/2020/420–028) through the African Research Initiative for Scientific Excellence pilot programme. The content of this Comment is the sole responsibility of the authors and can under no circumstances be regarded as reflecting the position of the EU, the African Academy of Sciences, or the African Union Commission. The content of this Comment is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of Allergy and Infectious Diseases, National Institutes of Health. All other authors declare no competing interests.

Polyfluorinated salicylic acid analogs do not interfere with siderophore biosynthesis

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb) is a leading cause of infectious disease mortality. The salicylic acid derived small molecule siderophores known as mycobactins are essential in vivo for iron acquisition of Mtb where iron is restricted in the host. Herein, we synthesize and explore the mechanism of action of polyfluorinated salicylic acid derivates, which were previously reported to possess potent antimycobacterial activity. We hypothesized fluorinated salicylic acid derivates may inhibit mycobactin biosynthesis through initial bioactivation and conversion to downstream metabolites that block late steps in assembly of the mycobactins. Enzymatic studies demonstrated that some of the fluorinated salicylic acid derivatives compounds were readily activated by the bifunctional adenylating enzyme MbtA, responsible for incorporation of salicylic acid into the mycobactin biosynthetic pathway; however, they did not inhibit mycobactin biosynthesis as confirmed by LS-MS/MS using an authentic synthetic mycobactin standard. Further mechanistic analysis of the most active derivative (Sal-4) using an MbtA-overexpressing Mtb strain as well as complementation studies with iron and salicylic acid revealed Sal-4 cannot be antagonized by overexpression of MbtA or through supplementation with iron or salicylic acid. Taken together, our results indicate the observed antimycobacterial activity of polyfluorinated salicylic acid derivative is independent of mycobactin biosynthesis.

Antimicrobial Peptides: A Promising Strategy for Anti-tuberculosis Therapeutics.

The high global burden of tuberculosis (TB) and the increasing emergence of the drugresistant (DR) strain of Mycobacterium tuberculosis (Mtb) emphasize the urgent need for novel antimycobacterial agents. Antimicrobial peptides (AMPs) are small peptides widely existing in a variety of organisms and usually have amphiphilic cationic structures, which have a selective affinity to the negatively charged bacterial cell wall. Besides direct bactericidal mechanisms, including interacting with the bacterial cell membrane and interfering with the biosynthesis of the cell wall, DNA, or protein, some AMPs are involved in the host's innate immunity. AMPs are promising alternative or complementary agents for the treatment of DR-TB, given their various antibacterial mechanisms and low cytotoxicity. A large number of AMPs, synthetic or natural, from human to bacteriophage sources, have displayed potent anti-mycobacterial activity in vitro and in vivo. In this review, we summarized the features, antimycobacterial activity, and mechanisms of action of the AMPs according to their sources. Although AMPs have not yet met the expectations for clinical application due to their low bioavailabilities, high cost, and difficulties in large-scale production, their potent antimycobacterial activity and action mechanisms, which are different from conventional antibiotics, make them promising antibacterial agents against DR-Mtb in the future.

Dimethyl itaconate is effective in host-directed antimicrobial responses against mycobacterial infections through multifaceted innate immune pathways

BackgroundItaconate, a crucial immunometabolite, plays a critical role in linking immune and metabolic functions to influence host defense and inflammation. Due to its polar structure, the esterified cell-permeable derivatives of itaconate are being developed to provide therapeutic opportunities in infectious and inflammatory diseases. Yet, it remains largely uncharacterized whether itaconate derivatives have potentials in promoting host-directed therapeutics (HDT) against mycobacterial infections. Here, we report dimethyl itaconate (DMI) as the promising candidate for HDT against both Mycobacterium tuberculosis (Mtb) and nontuberculous mycobacteria by orchestrating multiple innate immune programs.ResultsDMI per se has low bactericidal activity against Mtb, M. bovis Bacillus Calmette–Guérin (BCG), and M. avium (Mav). However, DMI robustly activated intracellular elimination of multiple mycobacterial strains (Mtb, BCG, Mav, and even to multidrug-resistant Mtb) in macrophages and in vivo. DMI significantly suppressed the production of interleukin-6 and -10, whereas it enhanced autophagy and phagosomal maturation, during Mtb infection. DMI-mediated autophagy partly contributed to antimicrobial host defenses in macrophages. Moreover, DMI significantly downregulated the activation of signal transducer and activator of transcription 3 signaling during infection with Mtb, BCG, and Mav.ConclusionTogether, DMI has potent anti-mycobacterial activities in macrophages and in vivo through promoting multifaceted ways for innate host defenses. DMI may bring light to new candidate for HDT against Mtb and nontuberculous mycobacteria, both of which infections are often intractable with antibiotic resistance.

Medicinal Plants as Therapeutic Alternatives to Combat Mycobacterium tuberculosis: A Comprehensive Review

Tuberculosis (TB) is a serious infectious disease caused by Mycobacterium tuberculosis (MTB) and a significant health concern worldwide. The main threat to the elimination of TB is the development of resistance by MTB to the currently used antibiotics and more extended treatment methods, which is a massive burden on the health care system. As a result, there is an urgent need to identify new, effective therapeutic strategies with fewer adverse effects. The traditional medicines found in South Asia and Africa have a reservoir of medicinal plants and plant-based compounds that are considered another reliable option for human beings to treat various diseases. Abundant research is available for the biotherapeutic potential of naturally occurring compounds in various diseases but has been lagging in the area of TB. Plant-based compounds, or phytoproducts, are being investigated as potential anti-mycobacterial agents by reducing bacterial burden or modulating the immune system, thereby minimizing adverse effects. The efficacy of these phytochemicals has been evaluated through drug delivery using nanoformulations. This review aims to emphasize the value of anti-TB compounds derived from plants and provide a summary of current research on phytochemicals with potential anti-mycobacterial activity against MTB. This article aims to inform readers about the numerous potential herbal treatment options available for combatting TB.

Histone deacetylase (HDAC) inhibitors- based drugs are effective to control Mycobacterium tuberculosis infection and promote the sensibility for rifampicin in MDR strain.

Tuberculosis (TB) is a major public health problem, which has been aggravated by the alarming growth of drug-resistant tuberculosis. Therefore, the development of a safer and more effective treatment is needed. The aim of this work was repositioning and evaluate histone deacetylases (HDAC) inhibitors- based drugs with potential antimycobacterial activity. Using an in silico pharmacological repositioning strategy, three molecules that bind to the catalytic site of histone deacetylase were selected. Pneumocytes type II and macrophages were infected with Mycobacterium tuberculosis and treated with pre-selected HDAC inhibitors (HDACi). Subsequently, the ability of each of these molecules to directly promote the elimination of M. tuberculosis was evaluated by colony-forming unit (CFU)/mL. We assessed the expression of antimicrobial peptides and respiratory burst using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Aminoacetanilide (ACE), N-Boc-1,2-phenylenediamine (N-BOC), 1,3-Diphenylurea (DFU), reduce bacillary loads in macrophages and increase the production of β-defensin-2, LL-37, superoxide dismutase (SOD) 3 and inducible nitric oxide synthase (iNOS). While only the use of ACE in type II pneumocytes decreases the bacterial load through increasing LL-37 expression. Furthermore, the use of ACE and rifampicin inhibited the survival of intracellular multi-drug resistance M. tuberculosis. Our data support the usefulness of in silico approaches for drug repositioning to provide a potential adjunctive therapy for TB.

Discovery of small molecule inhibitors of Mycobacterium tuberculosis ClpC1: SAR studies and antimycobacterial evaluation

The emergence of drug-resistant strains of Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB) in humans, is a primary reason for treatment failure. Currently, only limited options are available for the management of multi-drug resistant TB, warranting the design of novel anti-TB drugs by exploiting newer targets. One of the caseinolytic protease (Clp) machinery components, an unfoldase known as ClpC1, has emerged as a distinct anti-TB drug target owing to its essential role in the pathogen's survival. The naturally occurring cyclic peptides targeting the Mtb ClpC1, exhibit potent antimycobacterial activity. However, the large, complex, and poor synthetic tractability of these peptides limit their clinical application. Identification of small molecule inhibitors of Mtb ClpC1 will be useful for future drug development. Here, we report the discovery of a bisquinoline chemotype from the screening of a small molecule chemical library against Mtb ClpC1. The hit molecule binds with ClpC1 and exhibits dose-dependent inhibition of its enzymatic activity by direct binding. The in vitro growth of Mtb is inhibited by the hit molecule at a minimum inhibitory concentration of 12.5 µM. Investigation of the structure–activity relationship by chemical synthesis underlines the requirement of the two quinoline rings, 9/10 carbon linker, and the importance of basic ring nitrogen for its inhibitory activity. To our knowledge, this is the first report on the systematic analysis of small molecule inhibitors of Mtb ClpC1.

The Struggle to End a Millennia-Long Pandemic: Novel Candidate and Repurposed Drugs for the Treatment of Tuberculosis.

This article provides an encompassing review of the current pipeline of putative and developed treatments for tuberculosis, including multidrug-resistant strains. The review has organized each compound according to its site of activity. To provide context, mention of drugs within current recommended treatment regimens is made, thereafter followed by discussion on recently developed and upcoming molecules at established and novel targets. The review is designed to provide a clinically applicable understanding of the compounds that are deemed most currently relevant, including those already under clinical study and those that have shown promising pre-clinical results. An extensive review of the efficacy and safety data for key contemporary drugs already incorporated into treatment regimens, such as bedaquiline, pretomanid, and linezolid, is provided. The three levels of the bacterial cell wall (mycolic acid, arabinogalactan, and peptidoglycan layers) are highlighted and important compounds designed to target each layer are delineated. Amongst others, the highly optimistic and potent anti-mycobacterial activity of agents such as BTZ-043, PBTZ 169, and OPC-167832 are emphasized. The evolving spectrum of oxazolidinones, such as sutezolid, delpazolid, and TBI-223, all aiming to exceed the efficacy achieved with linezolid yet offer a safer alternative to the potential toxicity, are reviewed. New and exciting prospective agents with novel mechanisms of impact against TB, including 3-aminomethyl benzoxaboroles and telacebec, are underscored. We describe new diaryloquinolines in development, striving to build on the immense success of bedaquiline. Finally, we discuss some of these compounds that have shown encouraging additive or synergistic benefit when used in combination, providing some promise for the future in treating this ancient scourge.

2,4-Disubstituted pyridine derivatives are effective against intracellular and biofilm-forming tubercle bacilli.

It was recently reported that 4-substituted picolinohydrazonamides carrying hydrophilic cyclic amines, such as morpholine and pyrrolidine, at the end of their thiosemicarbazide chain have potent antimycobacterial activity in vitro at concentrations below 1μg/ml. Here, two selected compounds, 2,4-disubstituted pyridine derivatives 11 and 15, revealed significant bactericidal activity against Mycobacterium tuberculosis localized intracellularly within human macrophages, as well as against biofilm-forming tubercle bacilli. Mutants were selected that were resistant to the investigated compounds at an efficiency similar to that identified in the presence of the first line antituberculosis drug rifampicin. The resistant mutants were viable in the presence of the tested compounds exclusively on solid media. Genome-wide sequencing of the mutants selected in the presence of compound 11 revealed the accumulation of nonsynonymous mutations in the mmpR5 gene encoding a transcriptional repressor of the MmpS5-MmpL5 efflux pump, whose upregulation has been associated with bedaquiline resistance. The depletion of MmpR5 in wild-type M. tuberculosis using CRISPR-Cas9 technology increased the resistance of this strain to compound 11. Mass spectrometry-based proteomics (LC-MS/MS) of wild-type tubercle bacilli growing in subinhibitory concentrations of compounds 11 or 15 revealed 15 overproduced proteins not detectable in the control cells, including virulence-related proteins.

Silver nanoparticles synthesized from the seaweed Sargassum polycystum and screening for their biological potential

World-wide antimicrobial resistant is biggest threat in global health. It requires the urgent need of multisectoral action for the scientific community to achieve the sustainable development Goals. Due to their antimicrobial properties, silver nanoparticles are potential activates to pathogens, which explains their potential for multiple applications in various fields. In the present studies, we evaluate the antimicrobial properties of a Sargassum polycystum algal extract, an unrivaled green synthetic method for producing -defined shaped seaweed silver nanoparticles. To confirm their structure and size, some characterization techniques are used, such as Absorption spectrophotometer (UV–VIS), Fourier transforms infrared spectroscopy (FTIR), Scanning electron Microscope (SEM), Transmission electron microscopy (TEM) and X-Ray diffraction (XRD). Evaluate the antibacterial and anti-mycobacterial activity using silver nanoparticles. The toxicity study of this silver nanoparticle has been done with the help of zebrafish larva. The biological nanoparticle having good antimicrobial activity against Staphylococcus aureus, Micrococcus luteus, Pseudomonas fluorescens and Candida albicans and also it shows potent activity against MTB H37Rv, SHRE sensitive MTB Rifampicin resistant MTB around 98%. Seaweed nanoparticles had lower toxicity for the survival of the fish larvae. In comparison, other dosages will arrest the cell cycle and leads to death. The present finding revealed that these seaweeds nanoparticles have potential anti-mycobacterial activity against pathogens at low concentrations. This makes them a potent source of antibacterial and anti-TB agents

Identification of novel inhibitors for mycobacterial polyketide synthase 13 via in silico drug screening assisted by the parallel compound screening with genetic algorithm-based programs.

Identifying small compounds capable of inhibiting Mycobacterium tuberculosis polyketide synthase 13 (Pks13), in charge of final step of mycolic acid biosynthesis, could lead to the development of a novel antituberculosis drug. This study screened for lead compounds capable of targeting M. tuberculosis Pks13 from a chemical library comprising 154,118 compounds through multiple in silico docking simulations. The parallel compound screening (PCS), conducted via two genetic algorithm-based programs was applied in the screening strategy. Out of seven experimentally validated compounds, four compounds showed inhibitory effects on the growth of the model mycobacteria (Mycobacterium smegmatis). Subsequent docking simulation of analogs of the promising leads with the assistance of PCS resulted in the identification of three additional compounds with potent antimycobacterial effects (compounds A1, A2, and A5). Further, molecular dynamics simulation predicted stable interaction between M. tuberculosis Pks13 active site and compound A2, which showed potent antimycobacterial activity comparable to that of isoniazid. The present study demonstrated the efficacy of in silico structure-based drug screening through PCS in antituberculosis drug discovery.