Confronting the scientific obstacles to global control of tuberculosis

A Comparative Analysis of Microscopy, Culture, and the Xpert Mycobacterium tuberculosis/Rifampicin Assay in Diagnosing Pulmonary Tuberculosis in Human Immunodeficiency-Positive Individuals

INTRODUCTION

Individuals with human immunodeficiency virus (HIV) infection have an increased likelihood of developing tuberculosis (TB). The primary objective of this study was to compare the diagnostic accuracy of microscopy, culture, and the Xpert Mycobacterium tuberculosis/Rifampicin (MTB/RIF) assay in the diagnosis of pulmonary TB in sputum samples of HIV-infected patients. The secondary objectives were to evaluate the sensitivity and specificity of these three methods along with a comparison of diagnostic approaches for detecting drug-resistant strains.

MATERIAL AND METHODS

This prospective, laboratory-based study was done in the Microbiology Department of IGIMS, Patna. The study included sputum samples of 102 individuals who were HIV-positive and exhibited symptoms indicative of tuberculosis.

RESULTS

Out of 102 individuals suspected of having tuberculosis, 18 tested positive for M. tuberculosis. Male individuals between the ages of 31 and 40 were more affected by both HIV and tuberculosis, and in most of these cases, their CD4 cell count was below 200 cells/µl. Among the 102 sputum samples collected, 18% (18 samples) were found to be positive using the Mycobacterium Growth Indicator Tube (MGIT) 960 liquid culture method. Two samples were contaminated, and 14.7% (15 cases) tested positive using the cartridge-based nucleic acid amplification test (CBNAAT) method. Additionally, 3.92% (four samples) were positive using the ZN staining method.

CONCLUSION

The study found that Xpert MTB/RIF outperformed other methods in identifying resistance to RIF, showed better agreement with gene sequencing results for RIF resistance, and had higher accuracy in detecting tuberculosis cases, including both smear-positive and smear-negative cases.

Optimized LC-MS/MS quantification of tuberculosis drug candidate macozinone (PBTZ169), its dearomatized Meisenheimer Complex and other metabolites, in human plasma and urine

Tuberculosis, and especially multidrug-resistant tuberculosis (MDR-TB), is a major global health threat which emphasizes the need to develop new agents to improve and shorten treatment of this difficult-to-manage infectious disease. Among the new agents, macozinone (PBTZ169) is one of the most promising candidates, showing extraordinary potency in vitro and in murine models against drug-susceptible and drug-resistant Mycobacterium tuberculosis. A previous analytical method using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was developed by our group to support phase I clinical trials of PBTZ169. These plasma sample analyses revealed the presence of several additional metabolites among which the most prominent was H₂PBTZ, a reduced species obtained by dearomatization of macozinone, one of the first examples of Meisenheimer Complex (MC) metabolites identified in mammals. Identification of these new metabolites required the optimization of our original method for enhancing the selectivity between isobaric metabolites as well as for ensuring optimal stability for H₂PBTZ analyses. Sample preparation methods were also developed for plasma and urine, followed by extensive quantitative validation in accordance with international bioanalytical method recommendations, which include selectivity, linearity, qualitative and quantitative matrix effect, trueness, precision and the establishment of accuracy profiles using β-expectation tolerance intervals for known and newer analytes. The newly optimized methods have been applied in a subsequent Phase Ib clinical trial conducted in our University Hospital with healthy subjects. H₂PBTZ was found to be the most abundant species circulating in plasma, underscoring the importance of measuring accurately and precisely this unprecedented metabolite. Low concentrations were found in urine for all monitored analytes, suggesting extensive metabolism before renal excretion.

Heterologous prime-boost BCG with DNA vaccine expressing fusion antigens Rv2299c and Ag85A improves protective efficacy against Mycobacterium tuberculosis in mice

The development of heterologous prime-boost regimens utilizing Bacille Calmette–Guerin (BCG) as the priming vaccine is a promising approach to improve the efficacy of vaccination against tuberculosis (TB). In this study, we examined the ability of a DNA vaccine that expressed a fusion of antigens Rv2299c and Ag85A to boost BCG immunity and protection against Mycobacterium tuberculosis (Mtb) in Balb/c mice. The fusion DNA vaccine was moderately immunogenic and afforded some protection when used on its own. After a priming BCG vaccination, the DNA boost significantly amplified Th1-type cell-mediated immunity compared to that resulting from either BCG or DNA immunization. In the DNA-boosted mice, Ag-specific CD4+ and CD8+ T cells that were mono-positive for IFN-γ alone were the most prominently expanded in infected lungs. The protective efficacy afforded by BCG against challenge infection was greatly improved by the DNA boost; bacterial loads were significantly reduced in both spleen and lung and histological damage in the lung was less. The use of a DNA vaccine containing the fusion antigens Rv2299c and Ag85A to boost BCG may be a good choice for the rational design of an efficient vaccination strategy against TB.

Next-Generation Metagenome Sequencing Shows Superior Diagnostic Performance in Acid-Fast Staining Sputum Smear-Negative Pulmonary Tuberculosis and Non-tuberculous Mycobacterial Pulmonary Disease

In this study, we explored the clinical value of next-generation metagenome sequencing (mNGS) using bronchoalveolar lavage fluid (BALF) samples from patients with acid-fast staining (AFS) sputum smear-negative pulmonary tuberculosis (PTB) and non-tuberculous mycobacterial pulmonary disease (NTM-PD). Data corresponding to hospitalized patients with pulmonary infection admitted to the hospital between July 2018 and July 2021, who were finally diagnosed with AFS sputum smear-negative PTB and NTM-PD, were retrospectively analyzed. Bronchoscopy data as well as mNGS, Xpert, AFS (BALF analysis), and T-SPOT (blood) data, were extracted from medical records. Thereafter, the diagnostic performances of these methods with respect to PTB and NTM-PD were compared. Seventy-one patients with PTB and 23 with NTM-PD were included in the study. The sensitivities of mNGS, Xpert, T-SPOT, and AFS for the diagnosis of PTB were 94.4% (67/71), 85.9% (61/71), 64.8% (46/71), and 28.2% (20/71), respectively, and the diagnostic sensitivity of mNGS combined with Xpert was the highest (97.2%, 67/71). The specificity of Xpert was 100%, while those of AFS and T-SPOT were 73.9% (17/23) and 91.3% (21/23), respectively. Further, the 23 patients with NTM-PD could be identified using mNGS, and in the population with immunosuppression, the sensitivities of mNGS, Xpert, T-SPOT, and AFS were 93.5% (29/31), 80.6% (25/31), 48.4% (15/31), and 32.3% (10/31), respectively, and the diagnostic sensitivity of mNGS combined with Xpert was the highest (100%, 31/31). The specificities of Xpert and T-SPOT in this regard were both 100%, while that of AFS was 40% (2/5). Furthermore, using mNGS, all the NTM samples could be identified. Thus, the analysis of BALF samples using mNGS has a high accuracy in the differential diagnosis of MTB and NTM. Further, mNGS combined with Xpert can improve the detection of MTB, especially in AFS sputum smear-negative samples from patients with compromised immune states or poor responses to empirical antibiotics.

Association of High-Speed Rail and Tuberculosis Transmission in Newly Integrated Regions: Quasi-Experimental Evidence from China

Objectives: The spread of tuberculosis (TB) is related to changes in the social network among the population and people’s social interactions. High-speed railway (HSR) fundamentally changed the integrated market across cities in China. This paper aims to examine the impact of HSR on TB transmission in newly integrated areas.

Methods: By exploiting the opening and operation of the first HSR in Sichuan province as a quasi-natural experiment, we have collected and used the economic, social, and demographic data of 183 counties in Sichuan province from 2013 to 2016.

Results: The new HSR line is associated with a 4.790 increase in newly diagnosed smear-positive TB cases per 100,000 people among newly integrated areas. On average, an additional increase of 34.178 newly diagnosed smear-positive TB cases occur every year in counties (or districts) covered by the new HSR.

Conclusion: HSR development has significantly contributed to the transmission of TB. The public health system in China needs to pay more attention to the influences of new, mass public transportation.

Intracellular Accumulation of Novel and Clinically Used TB Drugs Potentiates Intracellular Synergy

The therapeutic repertoire for tuberculosis (TB) remains limited despite the existence of many TB drugs that are highly active in in vitro models and possess clinical utility. Underlying the lack of efficacy in vivo is the inability of TB drugs to penetrate microenvironments inhabited by the causative agent, Mycobacterium tuberculosis, including host alveolar macrophages. Here, we determined the ability of the phenoxazine PhX1 previously shown to be active against M. tuberculosis in vitro to differentially penetrate murine compartments, including plasma, epithelial lining fluid, and isolated epithelial lining fluid cells. We also investigated the extent of permeation into uninfected and M. tuberculosis-infected human macrophage-like Tamm-Horsfall protein 1 (THP-1) cells directly and by comparing to results obtained in vitro in synergy assays. Our data indicate that PhX1 (4,750 ± 127.2 ng/ml) penetrates more effectively into THP-1 cells than do the clinically used anti-TB agents, rifampin (3,050 ± 62.9 ng/ml), moxifloxacin (3,374 ± 48.7 ng/ml), bedaquiline (4,410 ± 190.9 ng/ml), and linezolid (770 ± 14.1 ng/ml). Compound efficacy in infected cells correlated with intracellular accumulation, reinforcing the perceived importance of intracellular penetration as a key drug property. Moreover, we detected synergies deriving from redox-stimulatory combinations of PhX1 or clofazimine with the novel prenylated amino-artemisinin WHN296. Finally, we used compound synergies to elucidate the relationship between compound intracellular accumulation and efficacy, with PhX1/WHN296 synergy levels shown to predict drug efficacy. Collectively, our data support the utility of the applied assays in identifying in vitro active compounds with the potential for clinical development. IMPORTANCE This study addresses the development of novel therapeutic compounds for the eventual treatment of drug-resistant tuberculosis. Tuberculosis continues to progress, with cases of Mycobacterium tuberculosis (M. tuberculosis) resistance to first-line medications increasing. We assess new combinations of drugs with both oxidant and redox properties coupled with a third partner drug, with the focus here being on the potentiation of M. tuberculosis-active combinations of compounds in the intracellular macrophage environment. Thus, we determined the ability of the phenoxazine PhX1, previously shown to be active against M. tuberculosis in vitro, to differentially penetrate murine compartments, including plasma, epithelial lining fluid, and isolated epithelial lining fluid cells. In addition, the extent of permeation into human macrophage-like THP-1 cells and H37Rv-infected THP-1 cells was measured via mass spectrometry and compared to in vitro two-dimensional synergy and subsequent intracellular efficacy. Collectively, our data indicate that development of new drugs will be facilitated using the methods described herein.

Tuberculosis burden in immigrants and natives, adults and children, in Tuscany between 2000-2018

BACKGROUND

Updated data on epidemiology of tuberculosis are needed in Italy. The aim of this study is to evaluate trends in incidence and associated lethality of tuberculosis in immigrants compared with Italians.

METHODS

All tuberculosis cases diagnosed from 2000 to 2018 in 31 Tuscan hospitals were retrospectively identified.

RESULTS

In 10,827 tuberculosis cases 6715 were males (62%), 4312 (60%) were Italian-born. Hospitalization rate was 15.37/100,000 population/year. The most common comorbidity were liver disease (832/10,827; 7.7%), COPD (675/10,827; 6.2%), cancer (614/10,827; 5.7%). HIV was more frequent in the immigrants (p < 0.001). Extra-pulmonary tuberculosis cases (EPTB) were mainly localized in pleura (740/3,894, 19%) and lymph nodes (449/3,894, 11,5%). HIV was associated with an increased risk of EPTB (OR 3.51 95% CI 2.92-4.23, p < 0.0001). EPTB risk was increased in South Asian-born patients (OR 1.77, 95% CI 1.46-2.15, p < 0.0001) as well in African-born patients (OR 1.13, 95% CI 1.03-1.24, p = 0.0091), who were at risk for gastroenteric tuberculosis (OR 3.74, 95% CI 2.69-5.22, p < 0.0001). Overall mortality rate was 0.006 per 1000. Most of death cases (89%) were Italians (p < 0.02) and mainly affected by pulmonary tuberculosis (PTB).

CONCLUSIONS

In Tuscany, tuberculosis is still a health concern in terms of both morbidity and mortality.

Developments in the Synthesis of Mycobacterial Phenolic Glycolipids

The highly lipophilic outer barrier of mycobacteria, such as M. tuberculosis and M. leprae, is key to their virulence and intrinsic antibiotic resistance. Various components of this mycomembrane interact with the host immune system but many of these interactions remain ill-understood. This review covers several chemical syntheses of one of these components, mycobacterial phenolic glycolipids (PGLs), and outlines the interaction of these PGLs with the human immune system, as established using these well-defined pure compounds.

Total Synthesis of Thuggacin cmc-A and Its Structure Determination

The first total synthesis of thuggacin cmc-A and the determination of the absolute structure are described. The thuggacin family of antibiotics is of great interest due to the antibiotic activity against Mycobacterium tuberculosis. Based on the assumption that seven stereogenic centers in thuggacin cmc-A would share the same stereochemistry as thuggacin-A, all stereogenic centers of thuggacin cmc-A were strictly constructed in a stereocontrolled manner. The total synthesis allowed its stereostructure to be fully confirmed.

Intracellular localisation of Mycobacterium tuberculosis affects efficacy of the antibiotic pyrazinamide

To be effective, chemotherapy against tuberculosis (TB) must kill the intracellular population of the pathogen, Mycobacterium tuberculosis. However, how host cell microenvironments affect antibiotic accumulation and efficacy remains unclear. Here, we use correlative light, electron, and ion microscopy to investigate how various microenvironments within human macrophages affect the activity of pyrazinamide (PZA), a key antibiotic against TB. We show that PZA accumulates heterogeneously among individual bacteria in multiple host cell environments. Crucially, PZA accumulation and efficacy is maximal within acidified phagosomes. Bedaquiline, another antibiotic commonly used in combined TB therapy, enhances PZA accumulation via a host cell-mediated mechanism. Thus, intracellular localisation and specific microenvironments affect PZA accumulation and efficacy. Our results may explain the potent in vivo efficacy of PZA, compared to its modest in vitro activity, and its critical contribution to TB combination chemotherapy.

HLA-DR-Positive NK Cells Expand in Response to Mycobacterium Tuberculosis Antigens and Mediate Mycobacteria-Induced T Cell Activation

NK cells play an important role in the control of tuberculosis infection: they are not only able to kill the infected cells, but also control the activity of macrophages and development of the adaptive immune response. Still, there is little information on the role of specific NK cell subsets in this network. In this study, we focused on the mycobacteria-driven responses of the NK cells expressing HLA-DR – a type of MHC class II. We have revealed that this subset is increased in the peripheral blood of patients with primary diagnosed tuberculosis, and expands in response to in vitro stimulation with ultrasonically destroyed Mycobacterium tuberculosis cells (sonicate). The expanded HLA-DR⁺ NK cells had less differentiated phenotype, higher proliferative activity and increased expression of NKp30 and NKp46 receptors. HLA-DR⁺CD56^dim NK cells showed higher IFNγ production and degranulation level than the respective HLA-DR⁻ NK cells in response to both 24 h and 7 day stimulation with sonicate, while HLA-DR⁺CD56^bright NK cells mostly demonstarted similar high responsiveness to the same stimulating conditions as their HLA-DR⁻CD56^bright counterparts. After preliminary incubation with destroyed mycobacteria, cytokine-activated HLA-DR-expressing NK cells were able to mediate mycobacteria-induced and HLA-DR-dependent cytokine production in autologous CD4⁺ T cells. Thus, functionally active HLA-DR⁺ cells seem to be one of the NK cell subsets providing an important link to the adaptive immunity.

Comparative Performance of Line Probe Assay (Version 2) and Xpert MTB/RIF Assay for Early Diagnosis of Rifampicin-Resistant Pulmonary Tuberculosis

BACKGROUND

The emergence of drug-resistant tuberculosis (TB), is a major menace to cast off TB worldwide. Line probe assay (LPA; GenoType MTBDRplus ver. 2) and Xpert MTB/RIF assays are two rapid molecular TB detection/diagnostic tests. To compare the performance of LPA and Xpert MTB/RIF assay for early diagnosis of rifampicin-resistant (RR) TB in acid-fast bacillus (AFB) smear-positive and negative sputum samples.

METHODS

A total 576 presumptive AFB patients were selected and subjected to AFB microscopy, Xpert MTB/RIF assay and recent version of LPA (GenoType MTBDRplus assay version 2) tests directly on sputum samples. Results were compared with phenotypic culture and drug susceptibility testing (DST). DNA sequencing was performed with rpoB gene for samples with discordant rifampicin susceptibility results.

RESULTS

Among culture-positive samples, Xpert MTB/RIF assay detected Mycobacterium tuberculosis (Mtb) in 97.3% (364/374) of AFB smear-positive samples and 76.5% (13/17) among smear-negative samples, and the corresponding values for LPA test (valid results with Mtb control band) were 97.9% (366/374) and 58.8% (10/17), respectively. For detection of RR among Mtb positive molecular results, the sensitivity of Xpert MTB/RIF assay and LPA (after resolving discordant phenotypic DST results with DNA sequencing) were found to be 96% and 99%, respectively. Whereas, specificity of both test for detecting RR were found to be 99%.

CONCLUSION

We conclude that although Xpert MTB/RIF assay is comparatively superior to LPA in detecting Mtb among AFB smear-negative pulmonary TB. However, both tests are equally efficient in early diagnosis of AFB smear-positive presumptive RR-TB patients.

Pulling the Brakes on Fast and Furious Multiple Drug-Resistant (MDR) Bacteria

Life-threatening bacterial infections have been managed by antibiotics for years and have significantly improved the wellbeing and lifetime of humans. However, bacteria have always been one step ahead by inactivating the antimicrobial agent chemically or by producing certain enzymes. The alarming universal occurrence of multidrug-resistant (MDR) bacteria has compelled researchers to find alternative treatments for MDR infections. This is a menace where conventional chemotherapies are no longer promising, but several novel approaches could help. Our current review article discusses the novel approaches that can combat MDR bacteria: starting off with potential nanoparticles (NPs) that efficiently interact with microorganisms causing fatal changes in the morphology and structure of these cells; nanophotothermal therapy using inorganic NPs like AuNPs to destroy pathogenic bacterial cells; bacteriophage therapy against which bacteria develop less resistance; combination drugs that act on dissimilar targets in distinctive pathways; probiotics therapy by the secretion of antibacterial chemicals; blockage of quorum sensing signals stopping bacterial colonization, and vaccination against resistant bacterial strains along with virulence factors. All these techniques show us a promising future in the fight against MDR bacteria, which remains the greatest challenge in public health care.

Structure-activity relationship of natural and synthetic coumarin derivatives against Mycobacterium tuberculosis

Aim: Eight coumarin derivatives (1a-h) obtained from natural (-)-mammea A/BB (1) and 13 synthetic coumarins (2-14) had their cytotoxicity and biological activity evaluated against Mycobacterium tuberculosis H₃₇Rv reference strain and multidrug-resistant clinical isolates. Materials & methods: Anti-M. tuberculosis activity was evaluated by resazurin microtiter assay plate, and the cytotoxicity of natural and synthetic products using J774A.1 macrophages by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. Results: Compounds 1g, 5, 6, 12 and 14 were more active against M. tuberculosis H₃₇Rv and multidrug-resistant clinical isolates with MIC values ranging from 15.6 to 62.5 μg/ml. Conclusion: These results demonstrate that the coumarin derivatives were active against multidrug-resistant clinical isolates, becoming potential candidates to be used in the treatment of resistant tuberculosis.

Cell wall peptidoglycan in Mycobacterium tuberculosis: An Achilles' heel for the TB-causing pathogen

Tuberculosis (TB), caused by the intracellular pathogen Mycobacterium tuberculosis, remains one of the leading causes of mortality across the world. There is an urgent requirement to build a robust arsenal of effective antimicrobials, targeting novel molecular mechanisms to overcome the challenges posed by the increase of antibiotic resistance in TB. Mycobacterium tuberculosis has a unique cell envelope structure and composition, containing a peptidoglycan layer that is essential for maintaining cellular integrity and for virulence. The enzymes involved in the biosynthesis, degradation, remodelling and recycling of peptidoglycan have resurfaced as attractive targets for anti-infective drug discovery. Here, we review the importance of peptidoglycan, including the structure, function and regulation of key enzymes involved in its metabolism. We also discuss known inhibitors of ATP-dependent Mur ligases, and discuss the potential for the development of pan-enzyme inhibitors targeting multiple Mur ligases.

Prevalence of latent tuberculosis infection and associated risk factors in prison in East Wollega Zone of western Ethiopia

Background

Latent tuberculosis infection (LTBI) is the major source of active TB and is an obstacle to the strategy of World Health Organization to end TB by 2035. In Ethiopia, there are hundreds of prisons and they are conducive settings for the transmission of TB and could serve as the sources of infection to the general public. However, there is little data on the epidemiology of TB in prisons in Ethiopia. The objective of the present study was to estimate the prevalence of LTBI and evaluate associated risk factors in prisons in East Wollega Zone in western Ethiopia.

Methods

A cross-sectional design and systematic sampling technique were used to select 352 prisoners from a total of 2620 prisoners during the two months (May and June, 2019). The selected inmates were consented for their willingness to participate in the study. Thereafter, they were interviewed and 2ml of blood sample was collected from each prisoner and screened for LTBI using interferon-gamma release assay (IGRA). The data were analyzed using SPSS version 25 and logistic regression was used to model the likelihood of LTBI occurrence and to identify risk factors associated with LTBI.

Results

The prevalence of LTBI was 51.2% (95% CI: 46.45–57%) and higher prevalence was recorded in males (53%) than in females (43.5%) although the difference was not significant. Prisoners whose age ≥45 years (AOR = 2.48, 95%CI, 1.04–5.9), who chewed khat (AOR = 2.27; 95% CI, 1.27–4.19), who were prisoned over a year (AOR = 1.81, 95%CI, 1.04–3.18) and who were in overcrowded pens (AOR = 1.91, 95% CI, 1.002–3.65) were at higher risk of LTBI.

Conclusions

The prevalence of LTBI in prisoners in West Wollega Zone of western Ethiopia was high and could serve as sources of infection to the public. Hence optimum handling of prisoners, and regular follow up and treatment of TB cases in prisons were recommended to minimize the burden of TB in the Zone.

Molecular epidemiological study of multidrug-resistant tuberculosis isolated from sputum samples in Eastern Cape, South Africa

Drug-resistant tuberculosis prevalence is still a global challenge. Making it imperative to examine the molecular epidemiology of drug resistant tuberculosis. Molecular epidemiology methods can evaluate transmission patterns and risk factors, ascertain transmission cases of multidrug-resistant tuberculosis (MDR-TB) and furthermore determine transmission patterns in a human populace. This work focuses on MDR-TB isolates in distinguishing them into several species and genotyping the MDR-TB isolates, mainly for epidemiological studies using the genomic regions of difference and the spoligotyping techniques. A total of 184 deoxyribonucleic acid isolated from sputum samples that showed resistance against the two major first-line anti-tuberculosis drugs (Rifampicin and Isoniazid) were examined. The deoxyribonucleic acid samples were amplified with primers specific for each flanking region of the genomic regions of difference for the identification of different MTBC species. Isolates were further characterized into different lineages using the spoligotyping commercial kit. The M. tuberculosis species was detected in 83.7% (154/184) of the deoxyribonucleic acid isolates, followed by the M. caprae in 8.7% (16/184) and the least detected species was the M. africanum in 2.2% (4/184). Nineteen spoligotype international types (SITs) were identified in this study. The pre-existing shared types were from 94.6% (174/184) isolates with 1.1% (2/184) isolates recognized as orphans and 4.3% (8/184) isolates were not found in the SITVIT database. The predominant family (spoligotype) was the Beijing with 67.4% (124/184) strains. This study gives a general overview of drug resistant strains and the circulating strains in the Eastern Cape, South Africa and it shows that the common Mycobacteria in the province is the Beijing strain.

Phenazine Antibiotic-Inspired Discovery of Bacterial Biofilm-Eradicating Agents

Bacterial biofilms are surface-attached communities of slow-growing and non-replicating persister cells that demonstrate high levels of antibiotic tolerance. Biofilms occur in nearly 80 % of infections and present unique challenges to our current arsenal of antibiotic therapies, all of which were initially discovered for their abilities to target rapidly dividing, free-floating planktonic bacteria. Bacterial biofilms are credited as the underlying cause of chronic and recurring bacterial infections. Innovative approaches are required to identify new small molecules that operate through bacterial growth-independent mechanisms to effectively eradicate biofilms. One source of inspiration comes from within the lungs of young cystic fibrosis (CF) patients, who often endure persistent Staphylococcus aureus infections. As these CF patients age, Pseudomonas aeruginosa co-infects the lungs and utilizes phenazine antibiotics to eradicate the established S. aureus infection. Our group has taken a special interest in this microbial competition strategy and we are investigating the potential of phenazine antibiotic-inspired compounds and synthetic analogues thereof to eradicate persistent bacterial biofilms. To discover new biofilm-eradicating agents, we have established an interdisciplinary research program involving synthetic medicinal chemistry, microbiology and molecular biology. From these efforts, we have identified a series of halogenated phenazines (HPs) that potently eradicate bacterial biofilms, and future work aims to translate these preliminary findings into ground-breaking clinical advances for the treatment of persistent biofilm infections.

Exploring the Chemistry and Therapeutic Potential of Triazoles: A Comprehensive Literature Review

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Triazole is a valuable platform in medicinal chemistry, possessing assorted pharmacological properties, which could play a major role in the common mechanisms associated with various disorders like cancer, infections, inflammation, convulsions, oxidative stress and neurodegeneration. Structural modification of this scaffold could be helpful in the generation of new therapeutically useful agents. Although research endeavors are moving towards the growth of synthetic analogs of triazole, there is still a lot of scope to achieve drug discovery break-through in this area. Upcoming therapeutic prospective of this moiety has captured the attention of medicinal chemists to synthesize novel triazole derivatives. The authors amalgamated the chemistry, synthetic strategies and detailed pharmacological activities of the triazole nucleus in the present review. Information regarding the marketed triazole derivatives has also been incorporated. The objective of the review is to provide insights to designing and synthesizing novel triazole derivatives with advanced and unexplored pharmacological implications.

Structures of DPAGT1 Explain Glycosylation Disease Mechanisms and Advance TB Antibiotic Design

Protein N-glycosylation is a widespread post-translational modification. The first committed step in this process is catalysed by dolichyl-phosphate N-acetylglucosamine-phosphotransferase DPAGT1 (GPT/E.C. 2.7.8.15). Missense DPAGT1 variants cause congenital myasthenic syndrome and disorders of glycosylation. In addition, naturally-occurring bactericidal nucleoside analogues such as tunicamycin are toxic to eukaryotes due to DPAGT1 inhibition, preventing their clinical use. Our structures of DPAGT1 with the substrate UDP-GlcNAc and tunicamycin reveal substrate binding modes, suggest a mechanism of catalysis, provide an understanding of how mutations modulate activity (thus causing disease) and allow design of non-toxic “lipid-altered” tunicamycins. The structure-tuned activity of these analogues against several bacterial targets allowed the design of potent antibiotics for Mycobacterium tuberculosis, enabling treatment in vitro, in cellulo and in vivo, providing a promising new class of antimicrobial drug.

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Structures of DPAGT1 with UDP-GlcNAc and tunicamycin reveal mechanisms of catalysis

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DPAGT1 mutations in patients with glycosylation disorders modulate DPAGT1 activity

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Structures, kinetics and biosynthesis reveal role of lipid in tunicamycin

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Lipid-altered, tunicamycin analogues give non-toxic antibiotics against TB

Mycobacterium tuberculosis infection of host cells in space and time

Tuberculosis (TB) caused by the bacterial pathogen Mycobacterium tuberculosis (Mtb) remains one of the deadliest infectious diseases with over a billion deaths in the past 200 years (Paulson 2013). TB causes more deaths worldwide than any other single infectious agent, with 10.4 million new cases and close to 1.7 million deaths in 2017. The obstacles that make TB hard to treat and eradicate are intrinsically linked to the intracellular lifestyle of Mtb. Mtb needs to replicate within human cells to disseminate to other individuals and cause disease. However, we still do not completely understand how Mtb manages to survive within eukaryotic cells and why some cells are able to eradicate this lethal pathogen. Here, we summarise the current knowledge of the complex host cell-pathogen interactions in TB and review the cellular mechanisms operating at the interface between Mtb and the human host cell, highlighting the technical and methodological challenges to investigating the cell biology of human host cell-Mtb interactions.

Frequencies of regulatory subsets of CD4+ TH cells in peripheral blood in Mycobacterium Tuberculosis-Infected individuals and healthy contacts in a high-burden setting from Assam, Northeast India

Background

Mycobacterium tuberculosis (Mtb) adapts many strategies to persist and replicate inside human tissue. One such strategy is the manipulation of CD4+ TH cells for subset interconversion to regulatory subsets. The aim of the present study is to get an insight of dynamic changes of CD4+ TH cells to regulatory subsets, CD4+ CD25+ forkhead box P3 (Foxp3)+ T-cells and CD4+ CD25+ Foxp3+ programmed death molecule-1 (Foxp3+) T-cells, in peripheral blood in Mtb-infected individuals and healthy contacts in a high-burden setting from Assam, Northeast India.

Materials and Methods

A case-control study was conducted in newly diagnosed active pulmonary tuberculosis (APTBs) patients and 2 sets of controls: (i) individuals infected with latent tuberculosis infection (LTBI) and (ii) healthy close tuberculosis healthy contacts (HCs). The frequencies of different subsets of CD4+ cells with regulatory markers were measured in peripheral blood in 3 groups of study participants.

Results and Observations

Frequencies of CD4+ CD25+ Foxp3+ T-cells (1.84 ± 1.40 vs. 4.32 ± 1.82 vs. 11.30 ± 3.66), CD4+ CD25+ Foxp3+ PD1+ T-cells (0.37 ± 1.28 vs. 2.99 ± 3.69 vs. 14.54 ± 5.10) and ligand (PD-L1)-positive CD4+ TH cells (0.80 ± 0.45 vs. 2.28 ± 0.95 vs. 7.13 ± 2.02) were significantly increased from HCs to LTBIs to APTB patients, respectively (P < 0.0001). No significant changes in frequencies of total CD4+ cells were observed between APTBs (29.51 ± 11.93), LTBIs (29.23 ± 8.16) and HCs (28.16 ± 9.73) whereas the mean ratios of CD4+ to CD4+ CD25+ FoxP3+ were significantly decreased from 34.34 ± 47.56 in HCs to 7.96 ± 5.8 in LTBIs to 3.12 ± 2.58 in APTBs (P < 0.0001). Significant decrease in mean ratios of CD4+ CD25+ FoxP3+ to CD4+ CD25+ FoxP3+ PD1+ were also observed from 4.97 ± 1.09 in HCs to 1.44 ± 0.49 in LTBIs to 0.78 ± 0.72 in APTBs.

Conclusion

CD4+ TH cells change dynamically to regulatory subsets depending on the status of infection and a shift of response towards excessive regulatory T-cells, and PD-1/PD-L1 production may help in the development of active infection in latently infected individuals. These immunological parameters may be used, as potential biomarkers to see the changing dynamics of Mtb infection.

The application of metabolomics toward pulmonary tuberculosis research

In the quest to identify novel biomarkers for pulmonary tuberculosis (TB), high-throughput systems biology approaches such as metabolomics has become increasingly widespread. Such biomarkers have not only successfully been used for better disease characterization, but have also provided new insights toward the future development of improved diagnostic and therapeutic approaches. In this review, we give a summary of the metabolomics studies done to date, with a specific focus on those investigating various aspects of pulmonary TB, and the infectious agent responsible, Mycobacterium tuberculosis. These studies, done on a variety of sample matrices, including bacteriological culture, sputum, blood, urine, tissue, and breath, are discussed in terms of their intended research outcomes or future clinical applications. Additionally, a summary of the research model, sample cohort, analytical apparatus and statistical methods used for biomarker identification in each of these studies, is provided.

Future Path Toward TB Vaccine Development: Boosting BCG or Re-educating by a New Subunit Vaccine

Tuberculosis (TB), an infectious disease caused by Mycobacterium tuberculosis (Mtb), kills 5,000 people per day globally. Rapid development and spread of various multi drug-resistant strains of Mtb emphasize that an effective vaccine is still the most cost-effectives and efficient way of controlling and eradicating TB. Bacillus Calmette-Guerin (BCG), the only licensed TB vaccine, still remains the most widely administered human vaccine, but is inefficient in protecting from pulmonary TB in adults. The protective immunity afforded by BCG is thought to wane with time and considered to last only through adolescent years. Heterologous boosting of BCG-primed immune responses using a subunit vaccine represents a promising vaccination approach to promote strong cellular responses against Mtb. In our earlier studies, we discovered lipopeptides of ESAT-6 antigen with strong potential as a subunit vaccine candidate. Here, we have investigated that potential as a booster to BCG vaccine in both a pre-exposure preventive vaccine and a post-exposure therapeutic vaccine setting. Surprisingly, our results demonstrated that boosting BCG with subunit vaccine shortly before Mtb challenge did not improve the BCG-primed immunity, whereas the subunit vaccine boost after Mtb challenge markedly improved the quantity and quality of effector T cell responses and significantly reduced Mtb load in lungs, liver and spleen in mice. These studies suggest that ESAT-6 lipopeptide-based subunit vaccine was ineffective in overcoming the apparent immunomodulation induced by BCG vaccine in Mtb uninfected mice, but upon infection, the subunit vaccine is effective in re-educating the protective immunity against Mtb infection. These important results have significant implications in the design and investigation of effective vaccine strategies and immunotherapeutic approaches for individuals who have been pre-immunized with BCG vaccine but still get infected with Mtb.

Antimycobacterial, Enzyme Inhibition, and Molecular Interaction Studies of Psoromic Acid in Mycobacterium tuberculosis: Efficacy and Safety Investigations

The current study explores the antimycobacterial efficacy of lichen-derived psoromic acid (PA) against clinical strains of Mycobacterium tuberculosis (M.tb). Additionally, the inhibitory efficacy of PA against two critical enzymes associated with M.tb, namely, UDP-galactopyranose mutase (UGM) and arylamine-N-acetyltransferase (TBNAT), as drug targets for antituberculosis therapy were determined. PA showed a profound inhibitory effect towards all the M.tb strains tested, with minimum inhibitory concentrations (MICs) ranging between 3.2 and 4.1 µM, and selectivity indices (SIs) ranging between 18.3 and 23.4. On the other hand, the standard drug isoniazid (INH) displayed comparably high MIC values (varying from 5.4 to 5.8 µM) as well as low SI values (13.0–13.9). Interestingly, PA did not exhibit any cytotoxic effects on a human liver hepatocellular carcinoma cell line even at the highest concentration tested (75 µM). PA demonstrated remarkable suppressing propensity against UGM compared to standard uridine-5'-diphosphate (UDP), with 85.8 and 99.3% of inhibition, respectively. In addition, PA also exerted phenomenal inhibitory efficacy (half maximal inhibitory concentration (IC₅₀) value = 8.7 µM, and 77.4% inhibition) against TBNAT compared with standard INH (IC₅₀ value = 6.2 µM and 96.3% inhibition). Furthermore, in silico analysis validated the outcomes of in vitro assays, as the molecular interactions of PA with the active sites of UGM and TBNAT were unveiled using molecular docking and structure–activity relationship studies. Concomitantly, our findings present PA as an effective and safe natural drug plausible for use in controlling tuberculosis infections.

Ultrasound Assisted Synthesis of 4-(Benzyloxy)-N-(3-chloro-2-(substitutedphenyl)-4-oxoazetidin-1-yl) Benzamide as Challenging Anti-Tubercular Scaffold

A series of ten novel derivatives of 4-(benzyloxy)-N-(3-chloro-2-(substituted phenyl)-4-oxoazetidin-1-yl) benzamide 6a⁻j were synthesized in good yield from the key compound 4-(benzyloxy)-N'-(substituted benzylidene) benzo hydrazide, called Schiff 's bases 5a⁻j, by Staudinger reaction ([2 + 2] ketene-imine cycloaddition reaction) with chloro acetyl chloride in the presence of catalyst tri ethylamine and solvent dimethyl formamide (DMF), by using ultra-sonication as one of the green chemistry tools. All the synthesised compounds were evaluated for in vitro anti-tubercular activity against Mycobacterium tuberculosis (MTB) and most of them showed promising activity with an IC₅₀ value of less than 1 µg/mL. To establish the safety, all the synthesized compounds were further tested for cytotoxicity against the human cancer cell line HeLa and all 6a⁻j compounds were found to be non-cytotoxic in nature. The molecular docking study was carried out with essential enzyme InhA (FabI/ENR) of Mycobacterium responsible for cell wall synthesis which suggests that 6a and 6e are the most active derivatives of the series. The theoretical evaluation of cell permeability based on Lipinski's rule of five has helped to rationalize the biological results and hence the synthesized azetidinone derivatives 6a⁻j were also analyzed for physicochemical evaluation that is, absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties and the results showed that all the derivatives could comply with essential features required for a potential lead in the anti-tubercular drug discovery process.

An Efficient Buchwald-Hartwig/Reductive Cyclization for the Scaffold Diversification of Halogenated Phenazines: Potent Antibacterial Targeting, Biofilm Eradication, and Prodrug Exploration

Bacterial biofilms are surface-attached communities comprised of nonreplicating persister cells housed within a protective extracellular matrix. Biofilms display tolerance toward conventional antibiotics, occur in ∼80% of infections, and lead to >500000 deaths annually. We recently identified halogenated phenazine (HP) analogues which demonstrate biofilm-eradicating activities against priority pathogens; however, the synthesis of phenazines presents limitations. Herein, we report a refined HP synthesis which expedited the identification of improved biofilm-eradicating agents. 1-Methoxyphenazine scaffolds were generated through a Buchwald-Hartwig cross-coupling (70% average yield) and subsequent reductive cyclization (68% average yield), expediting the discovery of potent biofilm-eradicating HPs (e.g., 61: MRSA BAA-1707 MBEC = 4.69 μM). We also developed bacterial-selective prodrugs (reductively activated quinone-alkyloxycarbonyloxymethyl moiety) to afford HP 87, which demonstrated excellent antibacterial and biofilm eradication activities against MRSA BAA-1707 (MIC = 0.15 μM, MBEC = 12.5 μM). Furthermore, active HPs herein exhibit negligible cytotoxic or hemolytic effects, highlighting their potential to target biofilms.

Latent tuberculosis infection and associated risk indicators in pastoral communities in southern Ethiopia: a community based cross-sectional study

BACKGROUND

Research pertaining to the community-based prevalence of latent tuberculosis infection (LTBI) is important to understand the magnitude of this infection. This study was conducted to estimate LTBI prevalence and to identify associated risk factors in the Omo Zone of Southern Ethiopia.

METHODS

A community-based cross-sectional study was conducted in six South Omo districts from May 2015 to February 2016. The sample size was allocated to the study districts proportional to their population sizes. Participants were selected using a multi-stage sampling approach. A total of 497 adult pastoralists were recruited. Blood samples were collected from the study participants and screened for LTBI using a U.S. Food and Drug Administration approved interferon-gamma release assay (IGRA). Logistic regression was used to model the likelihood of LTBI occurrence and to identify risk factors associated with LTBI.

RESULTS

The prevalence of LTBI was 50.5% (95% CI: 46%, 55%) with no significant gender difference (49.8% among males versus 51.2% among females; Chi-square (χ2) = 0.10; P = 0.41) and marginally non-significant increasing trends with age (44.6% among those below 24 years and 59.7% in the age range of 45-64 years; χ2 = 6.91; P = 0.075). Being residence of the Dasanech District (adjusted odds ratio, AOR = 2.62, 95% CI: 1.30, 5.28; P = 0.007) and having a habit of eating raw meat (AOR = 2.89, 95% CI: 1.09, 7.66; P = 0.033) were significantly associated with an increased odds of being positive for LTBI. A large family size (size of 5 to 10) has significant protective effect against associated a reduced odds of being positive for LTBI compared to a family size of below 5 (AOR = 0.65, 95% CI: 0.42, 0.99; P = 0.045).

CONCLUSIONS

A high prevalence of LTBI in the South Omo Zone raises the concern that elimination of TB in the pastoral communities of the region might be difficult. Screening for and testing individuals infected with TB, independent of symptoms, may be an effective way to minimize the risk of disease spread.

Design, synthesis, and pharmacological evaluation of fluorinated azoles as anti-tubercular agents

Design, synthesis, and biological screening of 2,2-dimethyl-2,3-dihydrobenzofuran tethered 1,3,4-oxadiazole derivatives as anti-tubercular agents were described. The synthesis of the target compounds was conducted by a series of reaction schemes. All the synthesized compounds were characterized by IR, ¹ H NMR, ¹³ C NMR, and mass spectrometry. The therapeutic potential of the synthesized compounds was confirmed by molecular docking studies. Among the synthesized compounds, 12a, 12c, 12d, 12e, 12g, and 12j were found to be more active against non-replicating than against replicating cultures of Mycobacterium tuberculosis H37Ra ex vivo and in vitro. These compounds exhibit minimum inhibitory concentration (MIC) values in the range of 2.31-23.91 μg/mL. The cytotoxicity study was conducted against the cell lines THP-1, A549 and PANC-1, and the compounds were observed to be non-toxic to host cells. Molecular docking was conducted with InhA (FabI/ENR) and suggested the antimycobacterial potential of the synthesized compounds. The investigation presented here was found to be adventitious for the development of new therapeutic agents against Mycobacterium infection.

IL-6 release of Rv0183 antigen-stimulated whole blood is a potential biomarker for active tuberculosis patients

OBJECTIVE

New tests for diagnosing active tuberculosis (aTB) are urgently needed, and TB antigen-specific cell-mediated immunity can be expected to develop new testing methods of aTB.

MATERIALS AND METHODS

Rv0183 protein, the only monoglyceride lipase identified in mycobacteria, was used to stimulate freshly heparin-treated whole blood. The Rv0183-specific cytokines/chemokines response associated with aTB was screened firstly with 4 aTB patients and 4 LTBIs, and further evaluated in 192 suspected aTB patients and 372 healthy individuals.

RESULTS

Out of 71 cytokines/chemokines, the response of IL-6 against Rv0183 protein was found to be associated with aTB. The Rv0183-specific IL-6 response was significantly higher in aTB patients (n = 128) than in those with non-TB lung disease (n = 64) and in healthy individuals (n = 327) (p < 0.0001), and not affected by latent TB infection. In IGRA+ suspected active TB patients, the sensitivity, specificity, PPV and NPV of IL-6 response (with cutoff of 235.2 pg/ml) were 85.7%, 100%, 100% and 51.5% for diagnosing aTB, respectively. While in IGRA- ones, they were 87.5%, 80.5%, 60.9% and 95.0% with 174.2 pg/ml IL-6 response as cutoff, respectively.

CONCLUSIONS

These results clearly show that the Rv0183 antigen-specific IL-6 response has the potential to be used as an immune-diagnosis test for active TB in clinical practice.

Childhood tuberculosis is associated with decreased abundance of T cell gene transcripts and impaired T cell function

The WHO estimates around a million children contract tuberculosis (TB) annually with over 80 000 deaths from dissemination of infection outside of the lungs. The insidious onset and association with skin test anergy suggests failure of the immune system to both recognise and respond to infection. To understand the immune mechanisms, we studied genome-wide whole blood RNA expression in children with TB meningitis (TBM). Findings were validated in a second cohort of children with TBM and pulmonary TB (PTB), and functional T-cell responses studied in a third cohort of children with TBM, other extrapulmonary TB (EPTB) and PTB. The predominant RNA transcriptional response in children with TBM was decreased abundance of multiple genes, with 140/204 (68%) of all differentially regulated genes showing reduced abundance compared to healthy controls. Findings were validated in a second cohort with concordance of the direction of differential expression in both TBM (r2 = 0.78 p = 2x10-16) and PTB patients (r2 = 0.71 p = 2x10-16) when compared to a second group of healthy controls. Although the direction of expression of these significant genes was similar in the PTB patients, the magnitude of differential transcript abundance was less in PTB than in TBM. The majority of genes were involved in activation of leucocytes (p = 2.67E-11) and T-cell receptor signalling (p = 6.56E-07). Less abundant gene expression in immune cells was associated with a functional defect in T-cell proliferation that recovered after full TB treatment (p<0.0003). Multiple genes involved in T-cell activation show decreased abundance in children with acute TB, who also have impaired functional T-cell responses. Our data suggest that childhood TB is associated with an acquired immune defect, potentially resulting in failure to contain the pathogen. Elucidation of the mechanism causing the immune paresis may identify new treatment and prevention strategies.

Mycothiol acetyltransferase (Rv0819) of Mycobacterium tuberculosis is a potential biomarker for direct diagnosis of tuberculosis using patient serum specimens

Mycobacterium tuberculosis infection constitutes a global threat that results in significant morbidity and mortality worldwide. Efficient and early diagnosis of tuberculosis (TB) is of paramount importance for successful treatment. The aim of the current study is to investigate the mycobacterial mycothiol acetyltransferase Rv0819 as a potential novel biomarker for the diagnosis of active TB infection. The gene encoding Rv0819 was cloned and successfully expressed in Escherichia coli. The recombinant Rv0819 was purified using metal affinity chromatography and was used to raise murine polyclonal antibodies against Rv0819. The raised antibodies were employed for direct detection of Rv0819 in patient serum samples using dot blot assay and competitive enzyme-linked immunosorbent assay (ELISA). Serum samples were obtained from 68 confirmed new TB patients and 35 healthy volunteers as negative controls. The dot blot assay showed sensitivity of 64·7% and specificity of 100%, whereas the competitive ELISA assay showed lower sensitivity (54·4%) and specificity (88·57%). The overall sensitivity of the combined results of the two tests was found to be 89·7%. Overall, the mycobacterial Rv0819 is a potential TB serum biomarker that can be exploited, in combination with other TB biomarkers, for efficient and reliable diagnosis of active TB infection.

SIGNIFICANCE AND IMPACT OF THE STUDY

The early and accurate diagnosis of tuberculosis infection is of paramount importance for initiating treatment and avoiding clinical complications. Most current diagnostic tests have poor sensitivity and/or specificity and in many cases they are too expensive for routine diagnostic testing in resource-limited settings. In the current study, we examined a novel mycobacterial serum biomarker, namely mycothiol acetyltransferase Rv0819. The antigen was detectable in serum specimens of a significant number of tuberculosis patients. This article proves the importance of Rv0819 and paves the way towards its future use as a useful diagnostic marker for tuberculosis infection.

Multiplex analysis of plasma cytokines/chemokines showing different immune responses in active TB patients, latent TB infection and healthy participants

Interferon gamma release assays (IGRAs) have been widely used to diagnose Mycobacterium tuberculosis (MTB) infection. However, IGRAs cannot discriminate between active TB patients and latent TB infection (LTBI), and the sensitivity of IGRAs for MTB infection is suboptimal. Here, we analyzed cytokines/chemokines in MTB antigen-stimulated and -unstimulated plasma samples to identify host biomarkers that are associated with active TB and MTB infection. Active TB patients, subjects with LTBI and healthy participants were recruited. Seventy-one soluble cytokines and chemokines were tested using Luminex liquid array-based multiplexed immunoassays. For the 71 examined factors, our results indicated that the unstimulated levels of IL-8 _Nil, IP-10 _Nil, MIP-1a _Nil, and sIL-2Ra _Nil and the antigen stimulated levels of IL-8 _(Ag-Nil), VEGF _(Ag-Nil), and MCP-3 _(Ag-Nil) were potential biomarkers for differentiating between active TB and LTBI, with AUCs of 0.8, 0.86, 0.755, 0.845, 0.825, 0.812 and 0.75, respectively. The G-CSF _(Ag-Nil), GM-CSF _(Ag-Nil), IL-1a _(Ag-Nil), IL-2 _(Ag-Nil), IP-10 _(Ag-Nil), BCA-1 _(Ag-Nil) and Eotaxin-1 _(Ag-Nil) responses were significantly higher in patients with active TB and LTBI compared with healthy participants (p < 0.05), with AUCs of 0.922, 0.902, 0.908, 1.0, 0.937, 0.919 and 0.935, respectively. Our preliminary data suggest that unstimulated or stimulated levels of cytokines and chemokines could be used as host biomarkers for diagnosing active TB as well as additional biomarkers, except IFN-γ, for MTB infection.

The regulatory role of Mcl-1 in apoptosis of mouse peritoneal macrophage infected with M. tuberculosis strains that differ in virulence

PURPOSE

Myeloid cell leukaemia-1 (Mcl-1) is a valuable target in tumour treatments. However, several reports have suggested that Mcl-1 may play a role in tuberculosis infection. Therefore, we investigated the function of Mcl-1 in tuberculosis infection and the underlying regulatory mechanism.

METHODS

Mcl-1-shRNA was used to down-regulate Mcl-1 expression in BCG-, H37Ra-, H37Rv- and XJ-MTB-infected mouse peritoneal macrophages. TUNEL staining detected macrophage apoptosis. The colony-forming units (CFUs) were determined to assess the Mycobacterium tuberculosis (MTB) clearance after down-regulating Mcl-1. Immunohistochemical analysis of Mcl-1 expression in mouse peritoneal macrophages was performed. Haematoxylin and eosin staining detected pathologic damage of the liver, spleen, lung, and kidney in mice. Real-time PCR and Western blotting determined the expression of cytochrome-c in Mcl-1-shRNA-treated mouse peritoneal macrophages infected with MTB strains that differ in virulence.

RESULTS

Mcl-1-shRNA significantly promoted host macrophage apoptosis and cytochrome-c induction, and the apoptotic induction of the XJ-MTB and H37Rv strains was stronger than the H37Ra and BCG strains (P<0.05). Apoptotic protein cytochrome-c levels continued to increase in mouse peritoneal macrophages infected MTB before and after treatment, Caspase-8 levels only slightly increased after Mcl-1-shRNA-treated (P<0.05), but the increase of Cytochrome-c have no significant differences compared with Caspase-8 levels (P>0.05).

CONCLUSION

Mcl-1-shRNA intervention effectively down-regulated Mcl-1 expression, significantly increased host macrophage apoptosis, and induced cytochrome-c expression in mouse peritoneal macrophages infected with MTB strains of different virulence, and these changes were influenced by the virulence of the MTB strains. The mitochondria-mediated intrinsic apoptotic pathway play an important role before Mcl-1-shRNA-trated, and then with the extrinsic apoptotic pathway co-regulate host macrophage apoptosis.

A Highly Potent Class of Halogenated Phenazine Antibacterial and Biofilm-Eradicating Agents Accessed Through a Modular Wohl-Aue Synthesis

Unlike individual, free-floating planktonic bacteria, biofilms are surface-attached communities of slow- or non-replicating bacteria encased within a protective extracellular polymeric matrix enabling persistent bacterial populations to tolerate high concentrations of antimicrobials. Our current antibacterial arsenal is composed of growth-inhibiting agents that target rapidly-dividing planktonic bacteria but not metabolically dormant biofilm cells. We report the first modular synthesis of a library of 20 halogenated phenazines (HP), utilizing the Wohl-Aue reaction, that targets both planktonic and biofilm cells. New HPs, including 6-substituted analogues, demonstrate potent antibacterial activities against MRSA, MRSE and VRE (MIC = 0.003-0.78 µM). HPs bind metal(II) cations and demonstrate interesting activity profiles when co-treated in a panel of metal(II) cations in MIC assays. HP 1 inhibited RNA and protein biosynthesis while not inhibiting DNA biosynthesis using ³H-radiolabeled precursors in macromolecular synthesis inhibition assays against MRSA. New HPs reported here demonstrate potent eradication activities (MBEC = 0.59-9.38 µM) against MRSA, MRSE and VRE biofilms while showing minimal red blood cell lysis or cytotoxicity against HeLa cells. PEG-carbonate HPs 24 and 25 were found to have potent antibacterial activities with significantly improved water solubility. HP small molecules could have a dramatic impact on persistent, biofilm-associated bacterial infection treatments.

Bedaquiline versus placebo for management of multiple drug-resistant tuberculosis: A systematic review

Background:

Multidrug-resistant tuberculosis (MDR-TB) is associated with significant morbidity and mortality. Bedaquiline is the first drug approved for treating MDR-TB.

Objectives:

We performed a systematic review and meta-analysis to summarize the totality of all available evidence on the efficacy of bedaquiline for the management of MDR-TB.

Materials and Methods:

We searched the following PubMed and Cochrane Registry of Clinical Trials. Randomized controlled trials (RCTs) with a parallel design comparing bedaquiline versus any treatment for the management of MDR-TB in adults were eligible for inclusion. Data were pooled under a random effects model.

Results:

Two trials published as three manuscripts with a total of 207 patients were included. As per the Cochrane risk of bias tool, majority of parameter were labeled as high or unclear risk of bias. Bedaquiline compared with placebo was associated with a statistically significant decrease in time to conversion of positive sputum culture to negative at 8 and 24 weeks with a significant increase in mortality on long-term follow-up. There was no difference in completion rates between bedaquiline and placebo.

Conclusion:

Bedaquiline is an effective treatment modality for MDR-TB but needs to be balanced against significant mortality. Future Phase 3 RCTs are needed to make a conclusive recommendation.

Clinical and genomic responses to ultra-short course chemotherapy in spinal tuberculosis

Traditional treatments for spinal tuberculosis (TB) involve chemotherapy and surgery. In the present study, it has been identified that chemotherapy lasting <6 months [ultra-short course chemotherapy (UCCT)], rather than the 6-18 months of the traditional regimen, is effective in sustaining TB clearance following complete surgical debridement. This current study aims to compare the changes in peripheral blood gene expression prior to and following UCCT, subsequent to complete debridement of spinal TB lesions. The study includes 5 patients without TB and 27 patients with spinal, divided into three groups: Group 1 (untreated group, n=8); group 2 (UCCT treatment group, n=9); and group 3 (UCCT treatment 1 year follow-up group, n=10). Gene changes were detected using DNA microarray analysis, confirmed through reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and the results were examined using the DAVID Knowledgebase to identify the pathways and functions of differentially expressed genes. TB lesions were active in group 1, while groups 2 and 3 showed no signs of active TB, as indicated by clinical manifestations and imaging. Comparison of the transcription profiles of the control and study groups showed that treatment of spinal TB resulted in upregulation of genes that are associated with immune response pathways; RT-qPCR produced similar findings. In conclusion, these results indicate that UCCT is an effective treatment against TB following complete surgical debridement. Furthermore, DNA microarray analysis proved a useful tool to evaluate the effects of spinal TB treatment on the expression of genes associated with immune response pathways.

Rapid detection of Mycobacterium tuberculosis and rifampicin resistance in extrapulmonary tuberculosis and sputum smear-negative pulmonary suspects using Xpert MTB/RIF

BACKGROUND

Tuberculosis (TB) is a serious public health problem in developing countries such as Pakistan. Rapid diagnosis of TB and detection of drug resistance are very important for timely and appropriate management of multidrug-resistant TB (MDR-TB).

OBJECTIVE

The purpose of this study was to determine the diagnostic efficacy of the Xpert MTB/RIF assay for rapid diagnosis of TB and detection of rifampicin (RIF) resistance in extrapulmonary and smear-negative pulmonary TB suspects.

METHODS

A total of 98 bronchoalveolar lavage fluid (BALF) and 168 extrapulmonary specimens were processed by Xpert MTB/RIF. Culture results are considered as the gold standard for diagnosis of TB, and drug susceptibility testing for detection of RIF resistance. Diagnostic efficacy was measured in terms of sensitivity, specificity and positive and negative predictive values.

RESULTS

The Xpert MTB/RIF assay detected 40 (40.8 %) of 98 BALF of presumptive pulmonary TB and 60 (35.7 %) of 168 extrapulmonary specimens. Sensitivity and specificity of the Xpert MTB/RIF assay for detection of TB was 86 and 88.4 %, respectively. The positive predictive value was 71.5 % while negative predictive value was 95.1 %.

CONCLUSION

The Xpert MTB/RIF assay is a rapid and simple technique with high sensitivity and specificity for diagnosing TB and detecting drug resistance in extrapulmonary and smear-negative TB cases.

Pharmacokinetic-Pharmacodynamic modelling of intracellular Mycobacterium tuberculosis growth and kill rates is predictive of clinical treatment duration

Tuberculosis (TB) treatment is long and complex, typically involving a combination of drugs taken for 6 months. Improved drug regimens to shorten and simplify treatment are urgently required, however a major challenge to TB drug development is the lack of predictive pre-clinical tools. To address this deficiency, we have adopted a new high-content imaging-based approach capable of defining the killing kinetics of first line anti-TB drugs against intracellular Mycobacterium tuberculosis (Mtb) residing inside macrophages. Through use of this pharmacokinetic-pharmacodynamic (PK-PD) approach we demonstrate that the killing dynamics of the intracellular Mtb sub-population is critical to predicting clinical TB treatment duration. Integrated modelling of intracellular Mtb killing alongside conventional extracellular Mtb killing data, generates the biphasic responses typical of those described clinically. Our model supports the hypothesis that the use of higher doses of rifampicin (35 mg/kg) will significantly reduce treatment duration. Our described PK-PD approach offers a much needed decision making tool for the identification and prioritisation of new therapies which have the potential to reduce TB treatment duration.

Mycobacterium tuberculosis replicates within necrotic human macrophages

Mycobacterium tuberculosis triggers macrophage cell death by necrosis, but it is unclear how this affects bacterial replication. Lerner et al. show that this pathogen replicates within necrotic human macrophages before disseminating to other cells upon loss of plasma membrane integrity.

Mycobacterium tuberculosis modulation of macrophage cell death is a well-documented phenomenon, but its role during bacterial replication is less characterized. In this study, we investigate the impact of plasma membrane (PM) integrity on bacterial replication in different functional populations of human primary macrophages. We discovered that IFN-γ enhanced bacterial replication in macrophage colony-stimulating factor–differentiated macrophages more than in granulocyte–macrophage colony-stimulating factor–differentiated macrophages. We show that permissiveness in the different populations of macrophages to bacterial growth is the result of a differential ability to preserve PM integrity. By combining live-cell imaging, correlative light electron microscopy, and single-cell analysis, we found that after infection, a population of macrophages became necrotic, providing a niche for M. tuberculosis replication before escaping into the extracellular milieu. Thus, in addition to bacterial dissemination, necrotic cells provide first a niche for bacterial replication. Our results are relevant to understanding the environment of M. tuberculosis replication in the host.

Role and contribution of pulmonary CD103+ dendritic cells in the adaptive immune response to Mycobacterium tuberculosis

Despite international control programmes, the global burden of tuberculosis remains enormous. Efforts to discover novel drugs have largely focused on targeting the bacterium directly. Alternatively, manipulating the host immune response may represent a valuable approach to enhance immunological clearance of the bacilli, but necessitates a deeper understanding of the immune mechanisms associated with protection against Mycobacterium tuberculosis infection. Here, we examined the various dendritic cells (DC) subsets present in the lung and draining lymph nodes (LN) from mice intra-tracheally infected with M. tuberculosis. We showed that although limited in number, pulmonary CD103⁺ DCs appeared to be involved in the initial transport of mycobacteria to the draining mediastinal LN and subsequent activation of T cells. Using CLEC9A-DTR transgenic mice enabling the inducible depletion of CD103⁺ DCs, we established that this DC subset contributes to the control of mycobacterial burden and plays a role in the early activation of T cells, in particular CD8⁺ T cells. Our findings thus support a previously unidentified role for pulmonary CD103⁺ DCs in the rapid mobilization of mycobacteria from the lungs to the draining LN soon after exposure to M. tuberculosis, which is a critical step for the development of the host adaptive immune response.

Adult pulmonary tuberculosis as a pathological manifestation of hyperactive antimycobacterial immune response

The intricate relationship between tuberculosis (TB) and immune system remains poorly understood. It is generally believed that weakening of the immune response against Mycobacterium tuberculosis leads to reactivation of latent infection into the active pulmonary disease. However, heterogeneous nature of TB and failure of rationally designed vaccines in clinical trials raises serious questions against the simplistic view of TB as an outcome of weakened immunity. In the wake of accumulating human TB data, it is argued here that a hyperactive antimycobacterial immune response is to blame for the pathogenesis of pulmonary TB in immunocompetent adults. Direct and indirect evidence supporting this notion is presented in this article. Revisiting the role of immune system in TB pathogenesis will pave the way for effective anti-TB vaccines.

Rapid Diagnosis of Tuberculosis from Analysis of Urine Volatile Organic Compounds

The World Health Organization has called for simple, sensitive, and non-sputum diagnostics for tuberculosis. We report development of a urine tuberculosis test using a colorimetric sensor array (CSA). The sensor comprised of 73 different indicators captures high-dimensional, spatiotemporal signatures of volatile chemicals emitted by human urine samples. The sensor responses to 63 urine samples collected from 22 tuberculosis cases and 41 symptomatic controls were measured under five different urine test conditions. Basified testing condition yielded the best accuracy with 85.5% sensitivity and 79.5% specificity. The CSA urine assay offers desired features needed for tuberculosis diagnosis in endemic settings.

Genetic polymorphisms of IL-17A, IL-17F, TLR4 and miR-146a in association with the risk of pulmonary tuberculosis

Genetic factors affect host susceptibility to pathogens. In this population-based case control study, we explored the genetic polymorphisms of IL-17, TLR4 and miR-146a in association with pulmonary tuberculosis in a Chinese Han population. We recruited 1601 pulmonary tuberculosis patients matched with 1526 healthy controls and genotyped twelve functional single nucleotide polymorphisms (SNPs). After the correction for multiple comparisons, two SNPs (rs10759932 and rs2737190) in the TLR4 gene remained significant. Individuals carrying the rs2737190-AG genotype (vs. AA) had a significantly increased risk of either clinical tuberculosis (OR: 1.31, 95% CI: 1.11–1.53) or sputum smear-positive tuberculosis (OR: 1.35, 95% CI: 1.13–1.61). Stratification analysis revealed that the effects of genetic variations on tuberculosis were more evident among non-smokers. People with haplotype TLR4 rs10983755G–rs10759932C had a significantly increased risk of tuberculosis (OR: 3.43, 95% CI: 2.34–5.05). Moreover, we found that SNPs of rs3819024 in IL-17A and rs763780 in IL-17F were weakly related to a prognosis of tuberculosis. Our results suggest that genetic polymorphisms of IL-17 and TLR4 may play a role in host susceptibility to tuberculosis in the Chinese Han population. More work is necessary to identify specific causative variants of tuberculosis underlying the observed associations.