Potent Antimycobacterial Activity Research Articles

Recent Advancements in Benzothiazinones (BTZ) Analogs as DprE1 Inhibitor for Potent Antitubercular Therapeutics

AbstractBenzothiazinone analogs have emerged as a promising class of compounds having potent antimycobacterial activity, particularly against Mycobacterium tuberculosis, the pathogen responsible for tuberculosis. This review highlights the development of benzothiazinone analogs as potential antitubercular agents from the beginning to the recent advancement in the past decade. These compounds have shown potent activity, including drug‐resistant strains of Mycobacterium tuberculosis. Structure–activity relationship studies and modifications have improved their efficacy. Benzothiazinone analogs have favorable pharmacokinetic profiles and show promise in preclinical studies. Challenges include addressing resistance mechanisms and ensuring safety. Their unique mode of action and promising properties make them attractive candidates for the battle against drug‐resistant tuberculosis.

A network pharmacology-based approach to understand the mechanism of action of anti-mycobacterial activity of Acacia nilotica: a modelling and experimental study.

The rapid rise in drug-resistant tuberculosis poses a serious threat to public health and demands the discovery of new anti-mycobacterial agents. Medicinal plants are a proven potential source of bioactive compounds; however, identifying those responsible for the putative anti-mycobacterial action still remains a challenging task. In this study, we undertook a systematic network pharmacology approach to identify and evaluate anti-mycobacterial compounds from a traditional plant, Acacia nilotica, as a model system. The protein-protein interaction network revealed 17 key pathways in M. tuberculosis encompassing 40 unique druggable targets that are necessary for its growth and survival. The phytochemicals of A. nilotica were preferentially found to interfere with the cell division and cell wall biogenesis proteins, especially FtsZ and Mur. Notably, the compounds epigallocatechin, ellagic acid, chlorogenic acid, and D-pinitol were found to exhibit a potential polypharmacological effect against multiple proteins. Further, in vitro studies confirmed that the selected candidates, chlorogenic acid, and ellagic acid exhibited potent anti-mycobacterial activity (against M. smegmatis) with specific inhibition of purified M.tb FtsZ enzyme. Taken together, the present study demonstrates that network pharmacology combined with molecular docking can be utilized as an efficient approach to identify potential bioactive phytochemicals from natural products along with their mechanism of action. Hence, the compounds identified in this study can be potential lead candidates for developing novel anti-mycobacterial drugs, while the key proteins identified here can be potential drug targets.

Design and synthesis of Thieno[3, 2-b]pyridinone derivatives exhibiting potent activities against Mycobacterium tuberculosis in vivo by targeting Enoyl-ACP reductase

In this study, a series of novel thieno [3, 2-b]pyridinone derivatives were designed and synthesized using a scaffold hopping strategy. Six compounds showed potent anti-mycobacterial activity (minimum inhibitory concentration (MIC) ≤ 1 μg/mL) against Mycobacterium tuberculosis (Mtb) UAlRa. Compound 6c displayed good activity against Mtb UAlRv (MIC = 0.5–1 μg/mL). Compounds 6c and 6i also showed activity against Mtb UAlRa in macrophages and exhibited low cytotoxicity against LO-2 cells. The selected compounds displayed a narrow antibacterial spectrum, with no activity against representative Gram-positive, Gram-negative bacteria, as well as fungi. Furthermore, compound 6c demonstrated favorable oral pharmacokinetic properties with a T1/2 value of 47.99 h and exhibited good in vivo activity in an acute mouse model of tuberculosis (TB). The target of compound 6c was identified as a NADH-dependent enoyl-acyl carrier protein reductase (InhA) by genome sequencing of spontaneously compound 6c-resistant Mtb mutants, indicating that compound 6c may not require activation and can directly target InhA. In vitro antimicrobial assays against a recombinant M. smegmatis overexpressing the Mtb-InhA, along with InhA inhibition assays, confirmed that InhA is the target of thieno [3, 2-b]pyridinone derivatives. Overall, this study identified thieno [3, 2-b]pyridinone scaffold as a novel chemotype that is promising for the development of anti-TB agents.

Synthesis and antitubercular activities of acetamide-substituted benzazole derivatives

Multidrug-resistant Mycobacterium tuberculosis strains' increasing emergence and rapid spread necessitate the urgent development of innovative antimycobacterial agents. In pursuit of novel agents, a series of N-(benzazole-2-ylmethyl)-2-substituted phenylacetamide or N-(benzazole-2-ylmethyl)-2-(thiophen-2-yl)acetamide compounds (6-11) were synthesized. Their efficacy against multidrug-resistant Mycobacterium tuberculosis was assessed. Compounds exhibited potent antimycobacterial activity with minimum inhibitory concentrations (MIC) ranging from 1.05 to 4.10 µM and demonstrated low cytotoxicity towards fibroblast cell line (L929). ADMET predictions suggested that these synthesized compounds possess drug-like properties. Our findings offer a promising starting point for designing more selective and potent antimycobacterial agents.

Development of narrow-spectrum topoisomerase-targeting antibacterials against mycobacteria

New 2-pyrrolamidobenzothiazole-based inhibitors of mycobacterial DNA gyrase were discovered. Among these, compounds 49 and 51, show excellent antibacterial activity against Mycobacterium tuberculosis and Mycobacterium abscessus with a notable preference for mycobacteria. Both compounds can penetrate infected macrophages and reduce intracellular M. tuberculosis load. Compound 51 is a potent inhibitor of DNA gyrase (M. tuberculosis DNA gyrase IC50 = 4.1 nM, Escherichia coli DNA gyrase IC50 of <10 nM), selective for bacterial topoisomerases. It displays low MIC90 values (M. tuberculosis: 0.63 μM; M. abscessus: 2.5 μM), showing specificity for mycobacteria, and no apparent toxicity. Compound 49 not only displays potent antimycobacterial activity (MIC90 values of 2.5 μM for M. tuberculosis and 0.63 μM for M. abscessus) and selectivity for mycobacteria but also exhibits favorable solubility (kinetic solubility = 55 μM) and plasma protein binding (with a fraction unbound of 2.9 % for human and 4.7 % for mouse). These findings underscore the potential of fine-tuning molecular properties to develop DNA gyrase B inhibitors that specifically target the mycobacterial chemical space, mitigating the risk of resistance development in non-target pathogens and minimizing harm to the microbiome.

X-ray Single-Crystal Analysis, Pharmaco-Toxicological Profile and Enoyl-ACP Reductase-Inhibiting Activity of Leading Sulfonyl Hydrazone Derivatives

Taking into consideration the growing resistance towards currently available antimycobacterials, there is still an unmet need for the development of new chemotherapeutic agents to combat the infectious agents. This study presents X-ray single-crystal analysis to verify the structure of leading sulfonyl hydrazone 3b, which has proven its potent antimycobacterial activity against Mycobacterium tuberculosis H37Rv with an MIC value of 0.0716 μM, respectively, low cytotoxicity, and very high selectivity indexes (SI = 2216), and which has been fully characterized by Nuclear Magnetic Resonance (NMR) and High-Resolution Mass Spectrometry (HRMS) methods. Furthermore, this study assessed the ex vivo antioxidant activity, acute and subacute toxicity, and in vitro inhibition capacity against enoyl-ACP reductase of hydrazones 3a and 3b, as 3a was identified as the second leading compound in our previous research. Compared to isoniazid, compounds 3a and 3b demonstrated lower acute toxicity for intraperitoneal administration, with LD50 values of 866 and 1224.7 mg/kg, respectively. Subacute toxicity tests, involving the repeated administration of a single dose of the test samples per day, revealed no significant deviations in hematological and biochemical parameters or pathomorphological tissues. The compounds exhibited potent antioxidant capabilities, reducing malondialdehyde (MDA) levels and increasing reduced glutathione (GSH). Enzyme inhibition assays of the sulfonyl hydrazones 3a and 3b with IC50 values of 18.2 µM and 10.7 µM, respectively, revealed that enoyl acyl carrier protein reductase (InhA) could be considered as their target enzyme to exhibit their antitubercular activities. In conclusion, the investigated sulfonyl hydrazones display promising drug-like properties and warrant further investigation.

Discovery of potent antimycobacterial agents targeting lumazine synthase (RibH) of Mycobacterium tuberculosis

Tuberculosis (TB) continues to be a global health crisis, necessitating urgent interventions to address drug resistance and improve treatment efficacy. In this study, we validate lumazine synthase (RibH), a vital enzyme in the riboflavin biosynthetic pathway, as a potential drug target against Mycobacterium tuberculosis (M. tb) using a CRISPRi-based conditional gene knockdown strategy. We employ a high-throughput molecular docking approach to screen ~ 600,000 compounds targeting RibH. Through in vitro screening of 55 shortlisted compounds, we discover 3 compounds that exhibit potent antimycobacterial activity. These compounds also reduce intracellular burden of M. tb during macrophage infection and prevent the resuscitation of the nutrient-starved persister bacteria. Moreover, these three compounds enhance the bactericidal effect of first-line anti-TB drugs, isoniazid and rifampicin. Corroborating with the in silico predicted high docking scores along with favourable ADME and toxicity profiles, all three compounds demonstrate binding affinity towards purified lumazine synthase enzyme in vitro, in addition these compounds exhibit riboflavin displacement in an in vitro assay with purified lumazine synthase indicative of specificity of these compounds to the active site. Further, treatment of M. tb with these compounds indicate reduced production of flavin adenine dinucleotide (FAD), the ultimate end product of the riboflavin biosynthetic pathway suggesting the action of these drugs on riboflavin biosynthesis. These compounds also show acceptable safety profile in mammalian cells, with a high selective index. Hence, our study validates RibH as an important drug target against M. tb and identifies potent antimycobacterial agents.

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.

Facile green synthesis of silver nanoparticles derived from the medicinal plant Clerodendrum serratum and its biological activity against Mycobacterium species

The emergence of multidrug-resistant mycobacterial strains is a significant crisis that has led to higher treatment failure rates and more toxic and expensive medications for tuberculosis (TB). The urgent need to develop novel therapeutics has galvanized research interest towards developing alternative antimicrobials such as silver nanoparticles (AgNPs). The current study focused on the anti-mycobacterial activity of green-synthesized AgNPs and its polyethylene glycol encapsulated derivative (PEG-AgNPs) with improved stability using the leaves extract of Clerodendrum serratum. Different characterization methods were used to analyze them. DLS analysis revealed a lower polydispersity index of PEG-AgNPs, suggesting a more uniform size distribution than that of AgNPs. The HR-TEM results revealed that the AgNPs and PEG-AgNPs have predominantly spherical shapes in the size range of 9–35 nm and 15–60 nm, respectively, while positive values of Zeta potential indicate their stability. FTIR-ATR analysis confirmed the presence of functional groups responsible for reducing and capping the bio-reduced AgNPs, whereas the XRD data established its crystalline nature. Impressively, the PEG-AgNPs exhibited maximum inhibitory activity against different Tubercular and Non-Tuberculous Mycobacterium species i.e., Mycobacterium smegmatis, Mycobacterium fortuitum and Mycobacterium marinum, relative to those of AgNPs and Linezolid. The flow cytometry assay showed that the anti-mycobacterial action was mediated by an increase in cell wall permeability. Notably, the results of AFM confirm their ability to inhibit mycobacterial biofilm significantly. We demonstrated the nontoxic nature of these AgNPs, explicated by the absence of hemolytic activity against human RBCs. Overall, the results suggest that PEG-AgNPs could offer a novel therapeutic approach with potential anti-mycobacterial activity and can overcome the limitations of existing TB therapies.

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.

Synthesis and antibacterial evaluation of new naphthalimide-coumarin hybrids against multidrug-resistant S. aureus and M. tuberculosis

The rapid rise in antimicrobial resistance (AMR) has become a major threat to human health. Consequently, the constant search for new antibacterial agents that work against resistant organisms has become a global initiative. To discover new antibacterial agents with improved efficacy and activity against drug-resistant organisms, we designed and synthesized a series of new naphthalimide-coumarin hybrids and evaluated them for their antimicrobial activity against a panel of bacterial and mycobacterial strains. In the preliminary evaluation, compounds 7a, 7c, 7d, 7e, 7f, 7h, 7i, 7o, 7q, 20a and 20b exhibited potent inhibitory activity against S. aureus ATCC 29213 with MICs in the range of 0.5–32 µg/mL. Compounds 7c, 7d, 7f, 7h, 7i, 7o, 20a, and 20b also exhibited good inhibitory activity against S. epidermidis with MIC 1–16 µg/mL. All these compounds were found to be non-toxic to Vero cells (CC50 = >50) and exhibited a favorable selectivity index (SI = >12.5). Additionally, these compounds 7c, 7d, 7e, 7f, 7h, 7i, 7o, 20a and 20b have shown potent inhibition against various multidrug-resistant strains of S. aureus, including VRSA with MICs in the range of 0.5–16 µg/mL. Interestingly, compound 17b showed potent antimycobacterial activity against M. tuberculosis H37Rv with MIC 1 µg/mL and a favorable selectivity index. It also exhibited potent inhibitory activity against DR-Mtb with MIC 1 µg/mL. Topoisomerase enzyme inhibition assay was carried out to validate the mechanism of action. Furthermore, in silico studies were performed to investigate the binding mode and interactions at the active site of the target enzyme. These results highlight the potential of naphthalimide-coumarin hybrids as novel antimicrobial 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

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

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.