Repurposing and Revival of the Drugs: A New Approach to Combat the Drug Resistant Tuberculosis

Inhibition of leukotriene-B4 signalling-mediated host response to tuberculosis is a potential mode of adjunctive host-directed therapy

Treatment of tuberculosis (TB) is faced with several challenges including the long treatment duration, drug toxicity and tissue pathology. Host-directed therapy provides promising avenues to find compounds for adjunctively assisting antimycobacterials in the TB treatment regimen, by promoting pathogen eradication or limiting tissue destruction. Eicosanoids are a class of lipid molecules that are potent mediators of inflammation and have been implicated in aspects of the host response against TB. Here, we have explored the blood transcriptome of pulmonary TB patients to understand the activity of leukotriene B4, a pro-inflammatory eicosanoid. Our study shows a significant upregulation in the leukotriene B4 signalling pathway in active TB patients, which is reversed with TB treatment. We have further utilized our in-house network analysis algorithm, ResponseNet, to identify potential downstream signal effectors of leukotriene B4 in TB patients including STAT1/2 and NADPH oxidase at a systemic as well as local level, followed by experimental validation of the same. Finally, we show the potential of inhibiting leukotriene B4 signalling as a mode of adjunctive host-directed therapy against TB. This study provides a new mode of TB treatment along with mechanistic insights which can be further explored in pre-clinical trials.

Unveiling the Clinical Diversity in Nontuberculous Mycobacteria (NTM) Infections: A Comprehensive Review

Once considered rare, nontuberculous mycobacterial (NTM) infections have garnered increasing attention in recent years. This comprehensive review provides insights into the epidemiology, clinical diversity, diagnostic methods, treatment strategies, prevention, and emerging research trends in NTM infections. Key findings reveal the global prevalence of NTM infections, their diverse clinical presentations affecting respiratory and extra-pulmonary systems, and the diagnostic challenges addressed by advances in microbiological, radiological, and immunological methods. Treatment complexities, especially drug resistance and patient adherence, are discussed, along with the vulnerability of special populations. The importance of early detection and management is underscored. Prospects in NTM research, including genomics, diagnostics, drug development, and multidisciplinary approaches, promise to enhance our understanding and treatment of these infections. This review encapsulates the multifaceted nature of NTM infections, offering a valuable resource for clinicians, researchers, and public health professionals.

Anti-Tuberculosis Activity of Three Carbapenems, Clofazimine and Nitazoxanide Using a Novel Ex Vivo Phenotypic Drug Susceptibility Model of Human Tuberculosis

We evaluated a novel physiological 3-D bioelectrospray model of the tuberculosis (TB) granuloma to test the activity of a known anti-TB drug, clofazimine; three carbapenems with potential activity, including one currently used in therapy; and nitazoxanide, an anti-parasitic compound with possible TB activity (all chosen as conventional drug susceptibility was problematical). PBMCs collected from healthy donors were isolated and infected with M. tuberculosis H37Rv lux (i.e., luciferase). Microspheres were generated with the infected cells; the anti-microbial compounds were added and bacterial luminescence was monitored for at least 21 days. Clavulanate was added to each carbapenem to inhibit beta-lactamases. M. tuberculosis (MTB) killing efficacy was dose dependent. Clofazimine was the most effective drug inhibiting MTB growth at 2 mg/L with good killing activity at both concentrations tested. It was the only drug that killed bacteria at the lowest concentration tested. Carbapenems showed modest initial activity that was lost at around day 10 of incubation and clavulanate did not increase killing activity. Of the carbapenems tested, tebipenem was the most efficient in killing MTB, albeit at a high concentration. Nitazoxanide was effective only at concentrations not achievable with current dosing (although this might partly have been an artefact related to extensive protein binding).

Drug re-engineering and repurposing: A significant and rapid approach to tuberculosis drug discovery

The prevalence of tuberculosis (TB) remains the leading cause of death from a single infectious agent, ranking it above all other contagious diseases. The problem to tackle this disease seems to become even worse due to the outbreak of SARS-CoV-2. Further, the complications related to drug-resistant TB, prolonged treatment regimens, and synergy between TB and HIV are significant drawbacks. There are several drugs to treat TB, but there is still no rapid and accurate treatment available. Intensive research is, therefore, necessary to discover newer molecular analogs that can probably eliminate this disease within a short span. An increase in efficacy can be achieved through re-engineering old TB-drug families and repurposing known drugs. These two approaches have led to the production of newer classes of compounds with novel mechanisms to treat multidrug-resistant strains. With respect to this context, we discuss structural aspects of developing new anti-TB drugs as well as examine advances in TB drug discovery. It was found that the fluoroquinolone, oxazolidinone, and nitroimidazole classes of compounds have greater potential to be further explored for TB drug development. Most of the TB drug candidates in the clinical phase are modified versions of these classes of compounds. Therefore, here we anticipate that modification or repurposing of these classes of compounds has a higher probability to reach the clinical phase of drug development. The information provided will pave the way for researchers to design and identify newer molecular analogs for TB drug development and also broaden the scope of exploring future-generation potent, yet safer anti-TB drugs.

Multiresidue antibiotic-metabolite quantification method using ultra-performance liquid chromatography coupled with tandem mass spectrometry for environmental and public exposure estimation

This manuscript describes a new multiresidue method utilising ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) via multiple reaction monitoring (MRM), for the identification and quantification of 58 antibiotics and their 26 metabolites, in various solid and liquid environmental matrices. The method was designed with a ‘one health’ approach in mind requiring multidisciplinary and multisectoral collaborative efforts. It enables comprehensive evaluation of antibiotic usage in surveyed communities via wastewater-based epidemiology, as well as allowing for the assessment of potential environmental impacts. The instrumental performance was very good, demonstrating linearity up to 3000 μg L⁻¹, and high accuracy and precision. The method accuracy in several compounds was significantly improved by dividing calibration curves into separate ranges. This was accompanied by applying a weighting factor (1/x). Microwave-assisted and/or solid-phase extraction of analytes from liquid and solid matrices provided good recoveries for most compounds, with only a few analytes underperforming. Method quantification limits were determined as low as 0.017 ng L⁻¹ in river water, 0.044 ng L⁻¹ in wastewater, 0.008 ng g⁻¹ in river sediment, and 0.009 ng g⁻¹ in suspended solids. Overall, the method was successfully validated for the quantification of 64 analytes extracted from aqueous samples, and 45 from solids. The analytes that underperformed are considered on a semi-quantitative basis, including aminoglycosides and carbapenems. The method was applied to both solid and liquid environmental matrices, whereby several antibiotics and their metabolites were quantified. The most notable antibiotic-metabolite pairs are three sulfonamides and their N-acetyl metabolites; four macrolides/lincomycins and their N-desmethyl metabolites; and five quinolone metabolites.

Low Rate of Acquired Linezolid Resistance in Multidrug-Resistant Tuberculosis Treated With Bedaquiline-Linezolid Combination

In this retrospective study in China, we aimed to: (1) determine the prevalence of linezolid (LZD) resistance among multidrug-resistant tuberculosis (MDR-TB)-infected patients; (2) monitor for dynamic LZD susceptibility changes during anti-TB treatment; and (3) explore molecular mechanisms conferring LZD resistance. A total of 277 MDR-TB patients receiving bedaquiline (BDQ)-containing regimens in 13 TB specialized hospitals across China were enrolled in the study. LZD and BDQ susceptibility rates were determined using the minimum inhibitory concentration (MIC) method, then DNA sequences of patient isolates were analyzed using Sanger sequencing to detect mutations conferring LZD resistance. Of 277 patients in our cohort, 115 (115/277, 41.5%) with prior LZD exposure yielded 19 (19/277, 6.9%) isolates exhibiting LZD resistance. The LZD resistance rate of LZD-exposed group isolates significantly exceeded the corresponding rate for non-exposed group isolates (P = 0.047). Genetic mutations were observed in 10 (52.6%, 10/19) LZD-resistant isolates, of which a Cys154Arg (36.8%, 7/19) substitution within ribosomal protein L3 was most prevalent. Analysis of sequential positive cultures obtained from 81 LZD-treated patients indicated that cultured organisms obtained from most patients (85.2%, 69/81) retained original LZD MIC values; however, organisms cultured later from two patients exhibited significantly increased MIC values that were attributed to the rplC substitution T460C. Overall, LZD resistance was detected in 6.9% of patients of an MDR-TB cohort in China. Low rate of acquired LZD resistance was noted in MDR-TB treated with BDQ-LZD combination.

Ion Transport Modulators as Antimycobacterial Agents

There is an urgent need for better and safer therapeutic interventions for tuberculosis (TB). We assessed the effects of FDA-approved ion transport modulators, namely, ambroxol HCl, amiloride HCl, diazoxide, digoxin, furosemide, hydrochlorothiazide (HCTZ), metformin, omeprazole, pantoprazole, phenytoin, verapamil, and drug X and Y on the growth of free and intracellular Mycobacterium bovis BCG. Free and intracellular M. bovis BCG were cultured in the presence or absence of the test drugs for 3 to 9 days and then quantified. For both free and intracellular bacteria, cultures that were exposed to furosemide, phenytoin, or drug Y yielded lower bacteria counts compared to drug-free controls (p < 0.05). The same was observed with diazoxide, HCTZ, verapamil, and drug X, but only for intracellular M. bovis BCG (p < 0.05). To assess the effects of the drugs on bactericidal activity of rifampicin, free and intracellular M. bovis BCG were treated with rifampicin alone or in combination with each of the thirteen test drugs for 3 to 9 days. For extracellular bacteria, higher bacteria clearance rates were observed in cultures exposed to rifampicin in combination with amiloride HCl, diazoxide, digoxin, furosemide, HCTZ, metformin, pantoprazole, phenytoin, drug X, or drug Y than those exposed to rifampicin alone, indicating that rifampicin had a synergistic effect with these test drugs. Rifampicin was also synergistic with ambroxol HCl, diazoxide, digoxin, furosemide, HCTZ, omeprazole, pantoprazole, phenytoin, verapamil, and drug X against intracellular M. bovis BCG. The antimycobacterial properties exhibited by the ion transport modulators in this study make them viable candidates as adjuncts to the current anti-TB regimens.

TB47 and clofazimine form a highly synergistic sterilizing block in a second-line regimen for tuberculosis in mice

Multidrug-resistant tuberculosis (MDR-TB) remains a serious public health threat worldwide. To date, the anti-TB activity of TB47 (T), an imidazopyridine amide class of antibiotics targeting QcrB in the electron transport chain, has not been systematically evaluated, especially in a new regimen against MDR-TB. This study employed both macrophage infection and a mouse model to test the activity of T alone or in combination with other antimicrobial agents. Different regimens containing amikacin (A), levofloxacin (L), ethambutol (E), and pyrazinamide (Z) + clofazimine (C)/T were evaluated in the mouse model. The bacterial burdens of mice from different groups were monitored at different time points while relapse was assessed 6 months after treatment cessation. Colonies obtained at relapse underwent drug susceptibility testing. We found that T exhibited highly synergistic bactericidal activity with C in all models. Adding T to ALEZC might shorten the MDR-TB treatment duration from ≥ 9 months to ≤ 5months, as five months of treatment with ALEZCT achieved zero relapse rates in 2 animal experiments. These findings indicate that T exhibits a highly synergistic sterilizing activity when combined with C. All isolates from relapsing mice remained sensitive to each drug, suggesting that the relapse was not due to drug resistance but rather associated with the type of regimen.

Potential anti-TB investigational compounds and drugs with repurposing potential in TB therapy: a conspectus

The latest WHO report estimates about 1.6 million global deaths annually from TB, which is further exacerbated by drug-resistant (DR) TB and comorbidities with diabetes and HIV. Exiguous dosing, incomplete treatment course, and the ability of the tuberculosis bacilli to tolerate and survive current first-line and second-line anti-TB drugs, in either their latent state or active state, has resulted in an increased prevalence of multidrug-resistant (MDR), extensively drug-resistant (XDR), and totally drug-resistant TB (TDR-TB). Although a better understanding of the TB microanatomy, genome, transcriptome, proteome, and metabolome, has resulted in the discovery of a few novel promising anti-TB drug targets and diagnostic biomarkers of late, no new anti-TB drug candidates have been approved for routine therapy in over 50 years, with only bedaquiline, delamanid, and pretomanid recently receiving tentative regulatory approval. Considering this, alternative approaches for identifying possible new anti-TB drug candidates, for effectively eradicating both replicating and non-replicating Mycobacterium tuberculosis, are still urgently required. Subsequently, several antibiotic and non-antibiotic drugs with known treatment indications (TB targeted and non-TB targeted) are now being repurposed and/or derivatized as novel antibiotics for possible use in TB therapy. Insights gathered here reveal that more studies focused on drug-drug interactions between licensed and potential lead anti-TB drug candidates need to be prioritized. This write-up encapsulates the most recent findings regarding investigational compounds with promising anti-TB potential and drugs with repurposing potential in TB therapy.

Metformin as Host-Directed Therapy for TB Treatment: Scoping Review

Tuberculosis (TB) disease is an international health concern caused by the bacteria Mycobacterium tuberculosis (Mtb). Evolution of multi-drug-resistant strains may cause bacterial persistence, rendering existing antibiotics ineffective. Hence, development of new or repurposing of currently approved drugs to fight Mtb in combination with existing antibiotics is urgently needed to cure TB which is refractory to current therapy. The shortening of TB therapy and reduction in lung injury can be achieved using adjunctive host-directed therapies. There is a wide range of probable candidates which include numerous agents permitted for the treatment of other diseases. One potential candidate is metformin, a Food and Drug Administration (FDA)-approved drug used to treat type 2 diabetes mellitus (DM). However, there is a scarcity of evidence supporting the biological basis for the effect of metformin as a host-directed therapy for TB. This scoping review summarizes the current body of evidence and outlines scientific gaps that need to be addressed in determining the potential role of metformin as a host-directed therapy.

Potential strategies for the management of drug-resistant tuberculosis

In the current scenario, the emergence of drug resistance in Mycobacterium tuberculosis is the consequence of the failure of conventional diagnostic and treatment approaches. To combat this global emergence of drug resistance, alternative approaches such as pathogen-centric (use of repurposed drugs, novel analogues of existing anti-TB drugs and novel compounds with a different mechanism of action), host-centric (immunomodulatory agents, therapeutic vaccines, immune and cellular therapies) and nano-based drug/vaccine delivery should be used singly or in combination. Diverse types of nano-carriers have assessed as auspicious diagnostic and drug delivery systems. In this focused review, we have suggested a long-term solution for combating antimicrobial resistance and also an attractive means to increase patient compliance and reduce treatment duration.

Celecoxib potentiates antibiotic uptake by altering membrane potential and permeability in Staphylococcus aureus

Background

We have shown previously that celecoxib enhances the antibacterial effect of antibiotics and has sensitized drug-resistant bacteria to antibiotics at low concentrations using in vitro and in vivo model systems and also using clinically isolated ESKAPE pathogens.

Objectives

To identify the mechanism of action of celecoxib in potentiating the effect of antibiotics on bacteria.

Methods

Toxicogenomic expression analysis of Staphylococcus aureus in the presence or absence of ampicillin, celecoxib or both was carried out by microarray followed by validation of microarray results by flow cytometry and real-time PCR analysis, cocrystal development and analysis.

Results

The RNA expression map clearly indicated a change in the global transcriptome of S. aureus in the presence of cells treated with ampicillin alone, which was similar to that of celecoxib-treated cells in co-treated cells. Several essential, non-essential and virulence genes such as α-haemolysin (HLA), enterotoxins and β-lactamase were differentially regulated in co-treated cells. Further detailed analysis of the expression data indicated that the ion transporters and enzymes of the lipid biosynthesis pathway were down-regulated in co-treated cells leading to decreased membrane permeability and membrane potential. Cocrystal studies using Powder-X-Ray Diffraction (PXRD) and differential scanning calorimetry (DSC) indicated interactions between celecoxib and ampicillin, which might help in the entry of antibiotics.

Conclusions

Although further studies are warranted, here we report that celecoxib alters membrane potential and permeability, specifically by affecting the Na+/K+ ion transporter, and thereby increases the uptake of ampicillin by S. aureus.

Targeting the Bacterial Membrane with a New Polycyclic Privileged Structure: A Powerful Tool To Face Staphylococcus aureus Infections

In this paper, a small series of anthracene-maleimide-based compounds was prepared and evaluated to assess the antimicrobial potential of this polycyclic core, a scaffold previously unexplored for new antibiotic development. Some of the new compounds showed appreciable anti-Staphylococcus aureus activity, together with good safety profiles. In particular, compound 13 proved to be the most promising of the series, showing remarkable antimicrobial activity toward planktonic and sessile bacterial cells within a mature preformed biofilm. The mechanism of action seems to be related to the ability of this compound to interfere with bacterial membrane functionality, probably through the targeting of key enzymes responsible for membrane redox homeostasis and energy production. The data reported confirm the ability of this polycyclic nucleus to behave as a new "privileged structure", suitable to be further exploited in the antimicrobial field.

Role of M.tuberculosis protein Rv2005c in the aminoglycosides resistance

Tuberculosis is an airborne infectious disease caused by Mycobacterium tuberculosis which threatens the globe. Aminoglycosides {Amikacin (AK) & Kanamycin (KM)} are WHO recommended second-line anti-TB drugs used against the treatment of drug-resistant tuberculosis. Aminoglycosides target the steps of protein translation machinery of M.tuberculosis. Several mechanisms have been put forward to elucidate the phenomena of aminoglycosides resistance but our knowledge is still insufficient. The aim of the study was to understand the involvement of Mycobacterium tuberculosis universal stress protein (Rv2005c) in aminoglycosides resistance and virulence. To establish the relationship of universal stress protein Rv2005c with AK & KM resistance, Rv2005c was cloned, expressed in E.coli BL21 using pQE2 expression vector and antimicrobial drug susceptibility testing (DST) was carried out. STRING-10 was also used to predict the interacting protein partners of Rv2005c. DST showed that the minimum inhibitory concentration of induced recombinant cells (Rv2005c) were five and four folds shifted with AK and KM E-strips, respectively. STRING-10 showed the interacting protein partners of Rv2005c. Overexpression of Rv2005c leads to shifting in MIC which might be signifying its involvement in the survival/resistance of Mycobacteria by inhibiting/modulating the effects of AK and KM released from the E-strips. Interactome also suggests that Rv2005c and its interacting protein partners are cumulatively involved in M.tuberculosis resistance, stresses, and latency.

In Vitro and In Vivo Activities of the Riminophenazine TBI-166 against Mycobacterium tuberculosis

The riminophenazine agent clofazimine (CFZ) is repurposed as an important component of the new short-course multidrug-resistant tuberculosis regimen and significantly shortens first-line regimen for drug-susceptible tuberculosis in mice. However, CFZ use is hampered by its unwelcome skin discoloration in patients. A new riminophenazine analog, TBI-166, was selected as a potential next-generation antituberculosis riminophenazine following an extensive medicinal chemistry effort. Here, we evaluated the activity of TBI-166 against Mycobacterium tuberculosis and its potential to accumulate and discolor skin. The in vitro activity of TBI-166 against both drug-sensitive and drug-resistant M. tuberculosis is more potent than that of CFZ. Spontaneous mutants resistant to TBI-166 were found at a frequency of 2.3 × 10^-7 in wild strains of M. tuberculosis TBI-166 demonstrates activity at least equivalent to that of CFZ against intracellular M. tuberculosis and in low-dose aerosol infection models of acute and chronic murine tuberculosis. Most importantly, TBI-166 causes less skin discoloration than does CFZ despite its higher tissue accumulation. The efficacy of TBI-166, along with its decreased skin pigmentation, warrants further study and potential clinical use.

Conditional Silencing by CRISPRi Reveals the Role of DNA Gyrase in Formation of Drug-Tolerant Persister Population in Mycobacterium tuberculosis

Drug tolerance in mycobacterial pathogens is a global concern. Fluoroquinolone (FQ) treatment is widely used for induction of persisters in bacteria. Although FQs that target DNA gyrase are currently used as second-line anti-tuberculosis (TB) drugs, little is known about their impact on Mycobacterium tuberculosis (Mtb) persister formation. Here we explored the CRISPRi-based genetic repression for better understanding the effect of DNA gyrase depletion on Mtb physiology and response to anti-TB drugs. We find that suppression of DNA gyrase drastically affects intra- and extracellular growth of Mtb. Interestingly, gyrase depletion in Mtb leads to activation of RecA/LexA-mediated SOS response and drug tolerance via induction of persister subpopulation. Chemical inhibition of RecA in gyrase-depleted bacteria results in reversion of persister phenotype and better killing by antibiotics. This study provides evidence that inhibition of SOS response can be advantageous in improving the efficacy of anti-TB drugs and shortening the duration of current TB treatment.

Quinolone-isoniazid hybrids: synthesis and preliminary in vitro cytotoxicity and anti-tuberculosis evaluation

Herein, we propose novel quinolones incorporating an INH moiety as potential drug templates against TB. The quinolone-based compounds bearing an INH moiety attached via a hydrazide-hydrazone bond were synthesised and evaluated against Mycobacterium tuberculosis H37Rv (MTB). The compounds were also evaluated for cytotoxicity against HeLa cell lines. These compounds showed significant activity (MIC₉₀) against MTB in the range of 0.2-8 μM without any cytotoxic effects. Compounds 10 (MIC₉₀; 0.9 μM), 11 (MIC₉₀; 0.2 μM), 12 (MIC₉₀; 0.8 μM) and compound 15 (MIC₉₀; 0.8 μM), the most active compounds in this series, demonstrate activities on par with INH and superior to those reported for the fluoroquinolones. The SAR analysis suggests that the nature of substituents at positions -1 and -3 of the quinolone nucleus influences anti-MTB activity. Aqueous solubility evaluation and in vitro metabolic stability of compound 12 highlights favourable drug-like properties for this compound class.

Prevalence and risk factors of tuberculosis in developing countries through health care workers

In the last two decades, tuberculosis (TB) have threatened the public across the globe and continuing new TB cases and their transmission pooled with the global emergence of drug-resistant strains present an enduring occupational risk for health care workers (HCWs). Since last decade, government and funding agencies has given a significant amount of funds to tackle the problem of TB infection among medical staff or HCW in hospitals of developing countries, but the effects of these efforts have not yet been reported. Working environments are the major risk factors for TB infections among the HCW in hospital settings. Twenty-two high burden countries endorsed to the preponderance of worldwide tuberculosis cases in 2015. Urgent preventive strategies and mediations are needed to ensure the safety and sustained availability of these exquisite healthcare resources. This timeline review will provide the theoretical basis of high TB burden among the HCW which can be used for further improvement in strategies for the prevention of TB infections in hospital settings and provide a reliable basis for improving the personal health of HCW or medical staff.

Potential Alternative Strategy against Drug Resistant Tuberculosis: A Proteomics Prospect

Mycobacterium tuberculosis is one of the deadliest human pathogen of the tuberculosis diseases. Drug resistance leads to emergence of multidrug-resistant and extremely drug resistant strains of M. tuberculosis. Apart from principal targets of resistance, many explanations have been proposed for drug resistance but some resistance mechanisms are still unknown. Recently approved line probe assay (LPA) diagnostics for detecting the resistance to first and second line drugs are unable to diagnose the drug resistance in M. tuberculosis isolates which do not have the mutations in particular genes responsible for resistance. Proteomics and bioinformatic tools emerged as direct approaches for identification and characterization of novel proteins which are directly and indirectly involved in drug resistance that could be used as potential targets in future. In future, these novel targets might reveal new mechanism of resistance and can be used in diagnostics or as drug targets.