Microbial pathogenesis of Mycobacterium tuberculosis: dawn of a discipline

Long non-coding RNA transcripts in Mycobacterium tuberculosis-host interactions

Tuberculosis (TB) persists as a significant health threat, affecting millions of people all over the world. Despite years of control measures, the elimination of TB has become a difficult task as morbidity and mortality rates remain unaffected for several years. Developing new diagnostics and therapeutics is paramount to keeping TB under control. However, it largely depends upon understanding the pathogenic mechanisms of Mycobacterium tuberculosis (Mtb), the causative agent of TB. Mtb is an intracellular pathogen capable of subverting the defensive functions of the immune cells, and it can survive and multiply within humans' mononuclear phagocytes. Emerging evidence indicates that long non-coding RNAs (lncRNAs), a class of RNA molecules with limited coding potential, are critical players in this intricate game as they regulate gene expression at transcriptional and post-transcriptional levels and also by chromatin modification. Moreover, they have been shown to regulate cellular processes by controlling the function of other molecules, such as DNA, RNA, and protein, through binding with them. Recent studies have shown that lncRNAs are differentially regulated in the tissues of TB patients and cells infected in vitro with Mtb. Some dysregulated lncRNAs are associated with essential roles in modulating immune response, apoptosis, and autophagy in the host cells, adding a new dimension to TB pathogenesis. In this article, we provide a comprehensive review of the recent literature in this field and the impact of lncRNAs in unraveling pathogenic mechanisms in TB. We also discuss how the studies involving lncRNAs provide insight into TB pathogenesis, especially Mtb-host interactions.

The effectiveness of community-wide screening for pulmonary tuberculosis: a systematic review

This systematic review evaluated the effectiveness of community-wide screening for pulmonary tuberculosis (TB) in high-burden areas by analysing randomised controlled trials (RCTs). The review focused on interventions offering TB screening to entire communities, comparing them to standard care or alternative approaches. The main outcome assessed was microbiologically confirmed TB diagnoses, including rates and prevalence. We searched MEDLINE, Embase, Cochrane Central Register of Controlled Trials, WHO Global Index Medicus, Web of Science, and trial registries up to 27 May 2024, without language restrictions. Screening, data extraction, and risk of bias assessment were done in duplicate. Results were not pooled. Certainty of the evidence was assessed using GRADE. PROSPERO: CRD42023453356. We included six cluster-RCTs after screening 2460 titles/abstracts and 86 full-text articles. The evidence for symptom screening was very uncertain. We found that sputum smear microscopy screening may result in little to no difference in the prevalence of culture-confirmed TB (n = 962,655, RR 1.09; 95% CI: 0.86-1.38, 1 RCT, low certainty evidence). Community-wide nucleic acid amplification test (NAAT) screening probably reduces the prevalence of NAAT-positive TB (n = 105,108, RR 0.56; 95% CI: 0.40-0.78, 1 RCT, moderate certainty evidence). Community-wide screening for pulmonary TB may reduce TB prevalence if done annually with an accurate screening test and high coverage.

Stealing survival: Iron acquisition strategies of Mycobacteriumtuberculosis

Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), faces iron scarcity within the host due to immune defenses. This review explores the importance of iron for Mtb and its strategies to overcome iron restriction. We discuss how the host limits iron as an innate immune response and how Mtb utilizes various iron acquisition systems, particularly the siderophore-mediated pathway. The review illustrates the structure and biosynthesis of mycobactin, a key siderophore in Mtb, and the regulation of its production. We explore the potential of targeting siderophore biosynthesis and uptake as a novel therapeutic approach for TB. Finally, we summarize current knowledge on Mtb's iron acquisition and highlight promising directions for future research to exploit this pathway for developing new TB interventions.

Comorbidity profiles among sputum-positive tuberculosis patients in Cameroon

Introduction

Comorbid non-communicable diseases (NCDs) like diabetes, cardiovascular diseases (CVD), kidney diseases, and hypertension, could have implications for tuberculosis (TB) treatment management and increase the disease burden amongst active TB patients.

Methods

This cross-sectional study aimed at profiling comorbidities amongst sputum-positive TB patients in the South West and Littoral regions of Cameroon and was relevant for improving disease management and public health interventions. Diabetes was defined by elevated blood glucose, body mass index (underweight: <18.5 kg/m2, normal: 18.5-<25.0 kg/m2, overweight: 25-<30 kg/m2 and obese: ≥30.0 kg/m2) and hypertension by elevated blood pressure levels (i.e., systolic ≥130 mmHg or diastolic ≥80 mmHg). Socio-demographic and clinical data were collected using case report forms. Descriptive analysis was performed, bivariate logistic regression analysis was computed with at least one comorbidity as the dependent variable (global model) and a multivariable logistic regression analysis was done to provide adjusted odds ratios (final model). The covariate with the highest p-value was removed until p < 0.25 cut-off, using R software version 4.3.1. p-value <0.05 at 95% confidence interval was considered statistically significant.

Results

Five hundred and forty-nine sputum-positive microscopically confirmed active TB patients were enrolled into this study. Two-thirds (65.8%) of the total patients were male. Overall, 56 sputum-positive TB patients had at least one non-communicable disease, thus a prevalence of 10.2% (95% CI = 7.9-13.0). The most frequently recorded NCD was diabetes 4.4% (95% CI = 3.1-6.7) followed by kidney disease 2% (95% CI = 1.1-3.6), hypertension 0.9% (95% CI = 0.4-2.2), and CVD 0.91% (95% CI = 0.4-2.2). Three TB patients (0.6%) had all four comorbidities examined. Age group (p < 0.001), and level of education (p = 0.049) were factors significantly associated with having at least one comorbidity.

Discussion

Our findings showed that diabetes was significantly the most prevalent comorbid NCD amongst sputum-positive TB patients (p < 0.001). HIV status, occupation, body mass index (BMI), and alcohol intake were not significantly associated with having at least one comorbidity. Implementing public health intervention programmes such as systematic screening of TB patients for NCDs especially diabetes is highly recommended for better control of these diseases.

Computational insights into the role of structurally diverse plant secondary metabolites as inhibitors against Imidazole Glycerol Phosphate Dehydratase of Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb) is one of the major causes of death worldwide and there is a pressing need for the development of novel drug leads. The Imidazole Glycerol Phosphate Dehydratase (IGPD) of Mtb is one of the key enzymes in the histidine biosynthesis pathway and has been recognized as the potentially underexploited drug target for anti-tuberculosis treatment. In the present study, 6063 structurally diverse plant secondary metabolites (PSM) were screened for their efficiency in inhibiting the catalytic activity of IGPD through molecular docking. The top 150 PSMs with the lowest binding energy represent the chemical classes, including Tannins (34%), Flavonoid Glycosides (14%), Terpene Glycosides (10%), Steroid Lactones (9.3%), Flavonoids (6.6%), Steroidal Glycosides (4.6%), etc. Bismahanine, Ashwagandhanolide, and Daurisoline form stable IGPD-inhibitor complexes with binding free energies of -291.3 ± 16.5, -279.0 ± 25.0, and -279.8 ± 17.6 KJ/mol, respectively, as determined by molecular dynamics simulations. These PSM demonstrated strong H-bond interactions with the amino acid residues Ile279, Arg281, and Lys276 in the catalytic region of IGPD, as revealed by structural snapshots. On the basis of our findings, these three PSM could be considered as possible leads against IGPD and should be explored in vitro and in vivo.Communicated by Ramaswamy H. Sarma.

Antigen specificity shapes antibody functions in tuberculosis

Tuberculosis (TB) is the number one infectious disease cause of death worldwide due to an incomplete understanding of immunity. Emerging data highlight antibody functions mediated by the Fc domain as immune correlates. However, the mechanisms by which antibody functions impact the causative agent Mycobacterium tuberculosis (Mtb) are unclear. Here, we examine how antigen specificity determined by the Fab domain shapes Fc effector functions against Mtb. Using the critical structural and secreted virulence proteins Mtb cell wall and ESAT-6 & CFP-10, we observe that antigen specificity alters subclass, antibody post-translational glycosylation, and Fc effector functions in TB patients. Moreover, Mtb cell wall IgG3 enhances disease through opsonophagocytosis of extracellular Mtb . In contrast, polyclonal and a human monoclonal IgG1 we generated targeting ESAT-6 & CFP-10 inhibit intracellular Mtb . These data show that antibodies have multiple roles in TB and antigen specificity is a critical determinant of the protective and pathogenic capacity.

Review canine tuberculosis - An emerging concern

Canine mycobacterial disease was first recognised over 100 years ago but is now an emerging concern. All reported cases of tuberculous disease in dogs have been caused by infection with one of three Mycobacterium tuberculosis-complex (MTBC) organisms (M. tuberculosis, Mycobacterium bovis, and Mycobacterium microti). Molecular PCR and interferon-gamma release assays offer alternative or complementary diagnostic pathways to that of specialist culture, which is limited by availability, sensitivity, and the time it takes to get a result. Optimised triple antimicrobial protocols offer an excellent chance of a successful outcome in dogs where treatment can be considered and is attempted. In this review, the clinical presentation, diagnosis, treatment, and prognosis of canine tuberculosis are discussed.

Temporal and cellular analysis of granuloma development in mycobacterial infected adult zebrafish

Because granulomas are a hallmark of tuberculosis pathogenesis, the study of the dynamic changes in their cellular composition and morphological character can facilitate our understanding of tuberculosis pathogenicity. Adult zebrafish infected with Mycobacterium marinum form granulomas that are similar to the granulomas in human patients with tuberculosis and therefore have been used to study host-mycobacterium interactions. Most studies of zebrafish granulomas, however, have focused on necrotic granulomas, while a systematic description of the different stages of granuloma formation in the zebrafish model is lacking. Here, we characterized the stages of granulomas in M. marinum-infected zebrafish, including early immune cell infiltration, nonnecrotizing granulomas, and necrotizing granulomas, using corresponding samples from patients with pulmonary tuberculosis as references. We combined hematoxylin and eosin staining and in situ hybridization to identify the different immune cell types and follow their spatial distribution in the different stages of granuloma development. The macrophages in zebrafish granulomas were shown to belong to distinct subtypes: epithelioid macrophages, foamy macrophages, and multinucleated giant cells. By defining the developmental stages of zebrafish granulomas and the spatial distribution of the different immune cells they contain, this work provides a reference for future studies of mycobacterial granulomas and their immune microenvironments.

Understanding bacterial pathogenicity: a closer look at the journey of harmful microbes

Bacteria are the most prevalent form of microorganisms and are classified into two categories based on their mode of existence: intracellular and extracellular. While most bacteria are beneficial to human health, others are pathogenic and can cause mild to severe infections. These bacteria use various mechanisms to evade host immunity and cause diseases in humans. The susceptibility of a host to bacterial infection depends on the effectiveness of the immune system, overall health, and genetic factors. Malnutrition, chronic illnesses, and age-related vulnerabilities are the additional confounders to disease severity phenotypes. The impact of bacterial pathogens on public health includes the transmission of these pathogens from healthcare facilities, which contributes to increased morbidity and mortality. To identify the most significant threats to public health, it is crucial to understand the global burden of common bacterial pathogens and their pathogenicity. This knowledge is required to improve immunization rates, improve the effectiveness of vaccines, and consider the impact of antimicrobial resistance when assessing the situation. Many bacteria have developed antimicrobial resistance, which has significant implications for infectious diseases and favors the survival of resilient microorganisms. This review emphasizes the significance of understanding the bacterial pathogens that cause this health threat on a global scale.

Polyketide synthases mutation in tuberculosis transmission revealed by whole genomic sequence, China, 2011-2019

Introduction: Tuberculosis (TB) is an infectious disease caused by a bacterium called Mycobacterium tuberculosis (Mtb). Previous studies have primarily focused on the transmissibility of multidrug-resistant (MDR) or extensively drug-resistant (XDR) Mtb. However, variations in virulence across Mtb lineages may also account for differences in transmissibility. In Mtb, polyketide synthase (PKS) genes encode large multifunctional proteins which have been shown to be major mycobacterial virulence factors. Therefore, this study aimed to identify the role of PKS mutations in TB transmission and assess its risk and characteristics. Methods: Whole genome sequences (WGSs) data from 3,204 Mtb isolates was collected from 2011 to 2019 in China. Whole genome single nucleotide polymorphism (SNP) profiles were used for phylogenetic tree analysis. Putative transmission clusters (≤10 SNPs) were identified. To identify the role of PKS mutations in TB transmission, we compared SNPs in the PKS gene region between "clustered isolates" and "non-clustered isolates" in different lineages. Results: Cluster-associated mutations in ppsA, pks12, and pks13 were identified among different lineage isolates. They were statistically significant among clustered strains, indicating that they may enhance the transmissibility of Mtb. Conclusion: Overall, this study provides new insights into the function of PKS and its localization in M. tuberculosis. The study found that ppsA, pks12, and pks13 may contribute to disease progression and higher transmission of certain strains. We also discussed the prospective use of mutant ppsA, pks12, and pks13 genes as drug targets.

A Rational Approach To Antitubercular Drug Design: Molecular Docking, Prediction of ADME Properties and Evaluation of Antitubercular Activity of Novel Isonicotinamide Scaffold

INTRODUCTION

One of the most devastating and leading diseases is Tuberculosis (TB), caused by Mycobacterium tuberculosis. Even though many synthetic drugs are available in the market, to increase the therapeutic efficacy and reduce toxicity. Isoniazid is the primary drug used in the treatment of tuberculosis.

METHODS

The main objective of the study is to perform molecular docking studies and synthesize the derivatives of isonicotinamide along with the anti-tubercular activity. The isonicotinamide derivatives (a-j) are prepared using isoniazid, carbon disulphate, methyl cyanide, and benzaldehyde derivatives and characterized by TLC, IR, 1HNMR, and Mass spectroscopy. The enzyme decaprenylphosphoryl-D-ribose oxidase (DprE1) of M. tuberculosis had good binding capacity with all the ligands revealed in molecular docking studies. In-vitro studies indicated that all the ligands showed anti-tuberculosis with strain M. tuberculosis.

RESULTS

The analysis was based on the binding energy and minimum inhibitory concentration (MIC). The highest and lowest binding energy is -4.22 Kcal/mol (f) and -8.45 Kcal/mol (d), and the MIC for compound d was found to be 644.22 nM. Among all the ligands, compound 5d has the most cytotoxic effect and lower IC50 values and better bioavailability.

CONCLUSION

This investigation helps in the development of better anti-tubercular therapy.

Global-scale GWAS associates a subset of SNPs with animal-adapted variants in M. tuberculosis complex

BACKGROUND

While Mycobacterium tuberculosis complex (MTBC) variants are clonal, variant tuberculosis is a human-adapted pathogen, and variant bovis infects many hosts. Despite nucleotide identity between MTBC variants exceeding 99.95%, it remains unclear what drives these differences. Markers of adaptation into variants were sought by bacterial genome-wide association study of single nucleotide polymorphisms extracted from 6,362 MTBC members from varied hosts and countries.

RESULTS

The search identified 120 genetic loci associated with MTBC variant classification and certain hosts. In many cases, these changes are uniformly fixed in certain variants while absent in others in this dataset, providing good discriminatory power in distinguishing variants by polymorphisms. Multiple changes were seen in genes for cholesterol and fatty acid metabolism, pathways previously proposed to be important for host adaptation, including Mce4F (part of the fundamental cholesterol intake Mce4 pathway), 4 FadD and FadE genes (playing roles in cholesterol and fatty acid utilization), and other targets like Rv3548c and PTPB, genes shown essential for growth on cholesterol by transposon studies.

CONCLUSIONS

These findings provide a robust set of genetic loci associated with the split of variant bovis and variant tuberculosis, and suggest that adaptation to new hosts could involve adjustments in uptake and catabolism of cholesterol and fatty acids, like the proposed specialization to different populations in MTB lineages by alterations to host lipid composition. Future studies are required to elucidate how the associations between cholesterol profiles and pathogen utilization differences between hosts and MTBC variants, as well as the investigation of uncharacterized genes discovered in this study. This information will likely provide an understanding on the diversification of MBO away from humans and specialization towards a broad host range.

Advances of new drugs bedaquiline and delamanid in the treatment of multi-drug resistant tuberculosis in children

Tuberculosis (TB) is a major public health problem, with nearly 10 million new cases and millions of deaths each year. Around 10% of these cases are in children, but only a fraction receive proper diagnosis and treatment. The spread of drug-resistant (DR) strain of TB has made it difficult to control, with only 60% of patients responding to treatment. Multi-drug resistant TB (MDR-TB) is often undiagnosed in children due to lack of awareness or under-diagnosis, and the target for children's DR-TB treatment has only been met in 15% of goals. New medications such as bedaquiline and delamanid have been approved for treating DR-TB. However, due to age and weight differences, adults and children require different dosages. The availability of child-friendly formulations is limited by a lack of clinical data in children. This paper reviews the development history of these drugs, their mechanism of action, efficacy, safety potential problems and current use in treating DR-TB in children.

A mathematical model for the co-dynamics of COVID-19 and tuberculosis

In this study, we formulated and analyzed a deterministic mathematical model for the co-infection of COVID-19 and tuberculosis, to study the co-dynamics and impact of each disease in a given population. Using each disease's corresponding reproduction number, the existence and stability of the disease-free equilibrium were established. When the respective threshold quantitiesR C , andR T are below unity, the COVID-19 and TB-free equilibrium are said to be locally asymptotically stable. The impact of vaccine (i.e., efficacy and vaccinated proportion) and the condition required for COVID-19 eradication was examined. Furthermore, the presence of the endemic equilibria of the sub-models is analyzed and the criteria for the phenomenon of backward bifurcation of the COVID-19 sub-model are presented. To better understand how each disease condition impacts the dynamics behavior of the other, we investigate the invasion criterion of each disease by computing the threshold quantity known as the invasion reproduction number. We perform a numerical simulation to investigate the impact of threshold quantities ( R C , R T ) with respect to their invasion reproduction number, co-infection transmission rate ( β c t ) , and each disease transmission rate ( β c , β t ) on disease dynamics. The outcomes established the necessity for the coexistence or elimination of both diseases from the communities. Overall, our findings imply that while COVID-19 incidence decreases with co-infection prevalence, the burden of tuberculosis on the human population increases.

Azide-Masked Fluorescence Turn-On Probe for Imaging Mycobacteria

A fluorescence turn-on probe, an azide-masked and trehalose-derivatized carbazole (Tre-Cz), was developed to image mycobacteria. The fluorescence turn-on is achieved by photoactivation of the azide, which generates a fluorescent product through an efficient intramolecular C-H insertion reaction. The probe is highly specific for mycobacteria and could image mycobacteria in the presence of other Gram-positive and Gram-negative bacteria. Both the photoactivation and detection can be accomplished using a handheld UV lamp, giving a limit of detection of 103 CFU/mL, which can be visualized by the naked eye. The probe was also able to image mycobacteria spiked in sputum samples, although the detection sensitivity was lower. Studies using heat-killed, stationary-phase, and isoniazid-treated mycobacteria showed that metabolically active bacteria are required for the uptake of Tre-Cz. The uptake decreased in the presence of trehalose in a concentration-dependent manner, indicating that Tre-Cz hijacked the trehalose uptake pathway. Mechanistic studies demonstrated that the trehalose transporter LpqY-SugABC was the primary pathway for the uptake of Tre-Cz. The uptake decreased in the LpqY-SugABC deletion mutants ΔlpqY, ΔsugA, ΔsugB, and ΔsugC and fully recovered in the complemented strain of ΔsugC. For the mycolyl transferase antigen 85 complex (Ag85), however, only a slight reduction of uptake was observed in the Ag85 deletion mutant ΔAg85C, and no incorporation of Tre-Cz into the outer membrane was observed. The unique intracellular incorporation mechanism of Tre-Cz through the LpqY-SugABC transporter, which differs from other trehalose-based fluorescence probes, unlocks potential opportunities to bring molecular cargoes to mycobacteria for both fundamental studies and theranostic applications.

Possible sex difference in latent tuberculosis infection risk among close tuberculosis contacts

OBJECTIVES

More men than women develop and die of tuberculosis (TB). Fewer data exist on sex differences in latent TB infection (LTBI). We assessed for potential sex differences in LTBI acquisition among close TB contacts.

METHODS

Regional Prospective Observational Research for TB-Brazil is an observational multi-center cohort of individuals with culture-confirmed pulmonary TB and their close contacts. Participants were enrolled from five sites in Brazil from June 2015 - June 2019. Close contacts were followed for 24 months after enrollment, with LTBI defined as a positive interferon-γ release assay (IGRA; QuantiFERON 3rd or 4th generation) at baseline or 6 months. We performed univariate, bivariate, and multivariable logistic regression and propensity-score weighted models to assess odds ratios (OR) and 95% confidence intervals (CI) for LTBI acquisition by birth sex among close contacts.

RESULTS

Of 1093, 504 (46%) female close contacts were IGRA positive compared to 295 of 745 (40%) men. The unadjusted OR for IGRA positivity among women vs men was 1.31 (95% CI: 1.08-1.58). Bivariate adjustments yielded ORs in women vs men ranging from 1.19 to 1.33 (P-value range: <0.01-0.07). Multivariable regression and weighted models yielded similar ORs in women vs men, of 1.14 (95% CI: 0.92-1.41) and 1.15 (95% CI: 0.94-1.40), respectively.

CONCLUSION

The point estimate for LTBI among close TB contacts in Brazil was higher in women, though less pronounced in multivariable models. If the sex difference in LTBI is confirmed in additional settings, studies of possible underlying differences in socio-behavioral factors or TB pathogenesis are warranted.

COVID-19 Syndemic: Convergence of COVID-19, Pulmonary Aspergillosis (CAPA), Pulmonary Tuberculosis, Type 2 Diabetes Mellitus, and Arterial Hypertension

Bacterial coinfections, which increase the severity of respiratory viral infections, are frequent causes of mortality in influenza pandemics but have not been well characterized in patients with Coronavirus disease 2019 (COVID-19). Moreover, the association of COVID-19 infection with pulmonary Mycobacterium tuberculosis disease (TB) and concurrent pulmonary fungal infection is not well known. The classification of patients with COVID-19-associated pulmonary aspergillosis (CAPA) using the current definitions for invasive fungal diseases has proven difficult. In this study, we aimed to provide information about three patients with underlying diseases ongoing with COVID-19 and co-infection with pulmonary TB, and with COVID-19-associated pulmonary aspergillosis (CAPA). At the time of hospital admission, each patient presented complications such as decompensated T2DM with diabetic ketoacidosis and/or hypertension. Findings of chest computed tomography and serum galactomannan by radioimmunoassay were useful for classifying them as possible CAPA. One of the three possible CAPA cases was fatal. These three cases are rare and are the first of their kind reported worldwide. The generation of reliable algorithms, early diagnosis, standardization of classification criteria, and the selection of specific and personalized treatments for COVID-19-associated opportunistic infections, including CAPA, are necessary to improve outcomes in these kinds of patients.

Mycobacterium tuberculosis Utilizes Host Histamine Receptor H1 to Modulate Reactive Oxygen Species Production and Phagosome Maturation via the p38MAPK-NOX2 Axis

Tuberculosis (TB), which is caused by the single pathogenic bacterium, Mycobacterium tuberculosis, is among the top 10 lethal diseases worldwide. This situation has been exacerbated by the increasing number of cases of multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB). Histamine is an organic nitrogenous compound that mediates a plethora of cell processes via different receptors. The expression of histamine receptor H1 (HRH1), one of the four histamine receptors identified to date was previously reported to be augmented by M. tuberculosis infection, although the underlying mechanism is unclear. In the present study, we applied confocal microscopy, flow cytometry, and Western blotting to show that HRH1 expression was enhanced in macrophages following mycobacterial infection. Furthermore, by combining techniques of gene knockdown, immunoprecipitation, intracellular bacterial burden analysis, fluorescence labeling, and imaging, we found that M. tuberculosis targeted the host HRH1 to suppress NOX2-mediated cROS production and inhibit phagosome maturation and acidification via the GRK2-p38MAPK signaling pathway. Our findings clarified the underlying mechanism of the M. tuberculosis and host HRH1 interaction and may provide useful information for the development of novel antituberculosis treatments.

Identification of protein biomarkers in host cerebrospinal fluid for differential diagnosis of tuberculous meningitis and other meningitis

Background and purpose

The diagnosis of tuberculous meningitis (TBM) is difficult due to the lack of sensitive methods. Identification of TBM-specific biomarkers in the cerebrospinal fluid (CSF) may help diagnose and improve our understanding of TBM pathogenesis.

Patients and methods

Of the 112 suspected patients with TBM prospectively enrolled in the study, 32 patients with inconclusive diagnosis, non-infectious meningitis, and long-term treatment with hormones and immunosuppressants were excluded. The expression of 8 proteins in the CSF was analyzed using ELISA in 22 patients with definite TBM, 18 patients with probable TBM, and 40 patients with non-TBM.

Results

Significant differences in the expression of 7 proteins were detected between the TBM and non-TBM groups (P < 0.01). Unsupervised hierarchical clustering (UHC) analysis revealed a disease-specific profile consisting of 7 differentially expressed proteins for TBM diagnosis, with an accuracy of 82.5% (66/80). Logistic regression with forward stepwise analysis indicated that a combination of 3 biomarkers (APOE_APOAI_S100A8) showed a better ability to discriminate TBM from patients with non-TBM [area under the curve (AUC) = 0.916 (95%CI: 0.857–0.976)], with a sensitivity of 95.0% (95%CI: 83.1–99.4%) and a specificity of 77.5% (95%CI: 61.5–89.2%).

Conclusion

Our results confirmed the potential ability of CSF proteins to distinguish TBM from patients with non-TBM and provided a useful panel for the diagnosis of TBM.

The chamber of secretome in Mycobacterium tuberculosis as a potential therapeutic target

Mycobacterium tuberculosis (MTB) causes one of the ancient diseases, Tuberculosis, affects people around the globe and its severity can be understood by its classification as a second infectious disease after COVID-19 and the 13th leading cause of death according to a WHO report. Despite having advanced diagnostic approaches and therapeutic strategies, unfortunately, TB is still spreading across the population due to the emergence of drug-resistance MTB and Latent TB infection (LTBI). We are seeking for effective approaches to overcome these hindrances and efficient treatment for this perilous disease. Therefore, there is an urgent need to develop drugs based on operative targeting of the bacterial system that could result in both efficient treatment and lesser emergence of MDR-TB. One such promising target could be the secretory systems and especially the Type 7 secretory system (T7SS-ESX) of Mycobacterium tuberculosis, which is crucial for the secretion of effector proteins as well as in establishing host-pathogen interactions of the tubercle bacilli. The five paralogous ESX systems (ESX-1 to EXS-5) have been observed by in silico genome analysis of MTB, among which ESX-1 and ESX-5 are substantial for virulence and mediating host cellular inflammasome. The bacterium growth and virulence can be modulated by targeting the T7SS. In the present review, we demonstrate the current status of therapeutics against MTB and focus on the function and cruciality of T7SS along with other secretory systems as a promising therapeutic target against Tuberculosis.

Correlation of serum amyloid A1 and interleukin-1beta in response to anti-tubercular therapy

BACKGROUND

Host biomarkers are needed to monitor the response to anti-tubercular therapy (ATT) for ensuring effective therapy and preventing drug-resistant tuberculosis. We sought to find the correlation between the serum levels of SAA1 and IL-1beta in response to ATT in adult patients with pulmonary TB (PTB) or extra-pulmonary TB (EPTB).

METHODS

Blood samples of 32 patients with PTB and 28 patients with EPTB were analyzed. The blood samples were collected at baseline, two months and six months following treatment initiation. SAA1 and IL-1beta levels were measured by enzyme linked immunosorbent assay (ELISA).

RESULTS

In the PTB group, the mean levels of SAA1 decreased significantly (p <0.001) after the intensive phase (two months) and continuous phase (six months) of ATT in comparison with the baseline value. IL-1beta values also decreased significantly (p = 0.005) after the intensive phase (two months) compared with the baseline values. In the EPTB group, there was a significant reduction in the mean serum level of SAA1 (p <0.001) and IL-1beta (p = 0.001) after the intensive phase (two months) in comparison with the baseline value, whereas the reduction at six months was not significant.

CONCLUSIONS

SAA1 and IL-1beta may be useful potential treatment-monitoring biomarkers, especially in the intensive phase of therapy for both PTB and EPTB.

Structural and Dynamic Insights into the W68L, L85P, and T87A Mutations of Mycobacterium tuberculosis Inducing Resistance to Pyrazinamide

Tuberculosis (TB), the most frequent bacterium-mediated infectious disease caused by Mycobacterium tuberculosis, has been known to infect humans since ancient times. Although TB is common worldwide, the most recent report by the WHO (World Health Organization) listed the three countries of India, China, and Russia with 27%, 14%, and 8% of the global burden of TB, respectively. It has been reported that resistance to TB drugs, particularly by the pncA gene to the pyrazinamide drug due to mutations, significantly affects the effective treatment of TB. Understanding the mechanism of drug resistance using computational methods is of great interest to design effective TB treatment, exploring the structural features with these tools. Thus, keeping in view the importance of these methods, we employed state-of-the-art computational methods to study the mechanism of resistance caused by the W68L, L85P, and T87A mutations recently reported in 2021. We employed a molecular docking approach to predict the binding conformation and studied the dynamic properties of each complex using molecular dynamics simulation approaches. Our analysis revealed that compared to the wildtype, these three mutations altered the binding pattern and reduced the binding affinity. Moreover, the structural dynamic features also showed that these mutations significantly reduced the structural stability and packing, particularly by the W68L and L85P mutations. Moreover, principal component analysis, free energy landscape, and the binding free energy results revealed variation in the protein's motion and the binding energy. The total binding free energy was for the wildtype -9.61 kcal/mol, W68L -7.57 kcal/mol, L85P -6.99 kcal/mol, and T87A -7.77 kcal/mol. Our findings can help to design a structure-based drug against the MDR (multiple drug-resistant) TB.

2Receptor Specific Ligand conjugated Nanocarriers: an Effective Strategy for Targeted Therapy of Tuberculosis

Tuberculosis (TB) is an ancient chronic disease caused by the bacillus Mycobacterium tuberculosis, which has affected mankind for more than 4,000 years. Compliance with the standard conventional treatment can assure recovery from tuberculosis, but emergence of drug resistant strains pose a great challenge for effective management of tuberculosis. The process of discovery and development of new therapeutic entities with better specificity and efficacy is unpredictable and time consuming. Hence, delivery of pre-existing drugs with improved targetability is the need of the hour. Enhanced delivery and targetability can ascertain improved bioavailability, reduced toxicity, decreased frequency of dosing and therefore better patient compliance. Nanoformulations are being explored for effective delivery of therapeutic agents, however optimum specificity is not guaranteed. In order to achieve specificity, ligands specific to receptors or cellular components of macrophage and Mycobacteria can be conjugatedto nanocarriers. This approach can improve localization of existing drug molecules at the intramacrophageal site where the parasites reside, improve targeting to the unique cell wall structure of Mycobacterium or improve adhesion to epithelial surface of intestine or alveolar tissue (lectins). Present review focuses on the investigation of various ligands like Mannose, Mycolic acid, Lectin, Aptamers etc. installed nanocarriers that are being envisaged for targeting antitubercular drugs.

Contribution of the Clp Protease to Bacterial Survival and Mitochondrial Homoeostasis

Fast adaptation to environmental changes ensures bacterial survival, and proteolysis represents a key cellular process in adaptation. The Clp protease system is a multi-component machinery responsible for protein homoeostasis, protein quality control, and targeted proteolysis of transcriptional regulators in prokaryotic cells and prokaryote-derived organelles of eukaryotic cells. A functional Clp protease complex consists of the tetradecameric proteolytic core ClpP and a hexameric ATP-consuming Clp-ATPase, several of which can associate with the same proteolytic core. Clp-ATPases confer substrate specificity by recognising specific degradation tags, and further selectivity is conferred by adaptor proteins, together allowing for a fine-tuned degradation process embedded in elaborate regulatory networks. This review focuses on the contribution of the Clp protease system to prokaryotic survival and summarises the current state of knowledge for exemplary bacteria in an increasing degree of interaction with eukaryotic cells. Starting from free-living bacteria as exemplified by a non-pathogenic and a pathogenic member of the Firmicutes, i.e., Bacillus subtilis and Staphylococcus aureus, respectively, we turn our attention to facultative and obligate intracellular bacterial pathogens, i.e., Mycobacterium tuberculosis, Listeria monocytogenes, and Chlamydia trachomatis, and conclude with mitochondria. Under stress conditions, the Clp protease system exerts its pivotal role in the degradation of damaged proteins and controls the timing and extent of the heat-shock response by regulatory proteolysis. Key regulators of developmental programmes like natural competence, motility, and sporulation are also under Clp proteolytic control. In many pathogenic species, the Clp system is required for the expression of virulence factors and essential for colonising the host. In accordance with its evolutionary origin, the human mitochondrial Clp protease strongly resembles its bacterial counterparts, taking a central role in protein quality control and homoeostasis, energy metabolism, and apoptosis in eukaryotic cells, and several cancer cell types depend on it for proliferation.

Mycobacterium tuberculosis Phosphoribosyltransferase Promotes Bacterial Survival in Macrophages by Inducing Histone Hypermethylation in Autophagy-Related Genes

Mycobacterium tuberculosis (Mtb) inhibits autophagy to promote its survival in host cells. However, the molecular mechanisms by which Mtb inhibits autophagy are poorly understood. Here, we report a previously unknown mechanism in which Mtb phosphoribosyltransferase (MtbPRT) inhibits autophagy in an mTOR, negative regulator of autophagy, independent manner by inducing histone hypermethylation (H3K9me2/3) at the Atg5 and Atg7 promoters by activating p38-MAPK- and EHMT2 methyltransferase-dependent signaling pathways. Additionally, we find that MtbPRT induces EZH2 methyltransferase-dependent H3K27me3 hypermethylation and reduces histone acetylation modifications (H3K9ac and H3K27ac) by upregulating histone deacetylase 3 to inhibit autophagy. In summary, this is the first demonstration that Mtb inhibits autophagy by inducing histone hypermethylation in autophagy-related genes to promote intracellular bacterial survival.

A Small Protein but with Diverse Roles: A Review of EsxA in Mycobacterium-Host Interaction

As a major effector of the ESX-1 secretion system, EsxA is essential for the virulence of pathogenic mycobacteria, such as Mycobacterium tuberculosis (Mtb) and Mycobacterium marinum (Mm). EsxA possesses an acidic pH-dependent membrane permeabilizing activity and plays an essential role by mediating mycobacterial escape from the phagosome and translocation to the cytosol for intracellular replication. Moreover, EsxA regulates host immune responses as a potent T-cell antigen and a strong immunoregulator. EsxA interacts with multiple cellular proteins and stimulates several signal pathways, such as necrosis, apoptosis, autophagy, and antigen presentation. Interestingly, there is a co-dependency in the expression and secretion of EsxA and other mycobacterial factors, which greatly increases the complexity of dissecting the precise roles of EsxA and other factors in mycobacterium-host interaction. In this review, we summarize the current understandings of the roles and functions of EsxA in mycobacterial infection and discuss the challenges and future directions.

Base excision repair pathways of bacteria: new promise for an old problem

Infectious diseases continue to be a major cause of human mortality. With the emergence of drug resistance, diseases that were long thought to have been curable by antibiotics are resurging. There is an urgent clinical need for newer antibiotics that target novel cellular pathways to overcome resistance to currently used therapeutics. The base excision repair (BER) pathways of the pathogen restore altered bases and safeguard the genomic integrity of the pathogen from the host's immune response. Although the BER machinery is of paramount importance to the survival of the pathogens, its potential as a drug target is largely unexplored. In this review, we discuss the importance of BER in different pathogenic organisms and the potential of its inhibition with small molecules.

Comparison of serum neopterin levels in pulmonary tuberculosis patients with positive acid fast bacilli and inactive pulmonary tuberculosis

BACKGROUND

Tuberculosis (TB) is caused by infection with Mycobacterium tuberculosis. Sometimes it is difficult to distinguish between active and inactive pulmonary TB based on chest X-ray images. TB biomarkers are needed to diagnose active TB when TB bacilli are not detected either through microscopic examination, culture or geneXpert MTB/Rif. Neopterin can be used as an additional diagnosis and therapy monitoring as well as assessing activation of macrophage cells. This study aims to examine and comparing serum neopterin levels in new cases of pulmonary TB with positive AFB and inactive pulmonary TB.

METHODS

This was an analytic study with Cross-Sectional design conducted in Dr. Soetomo General Hospital Surabaya, Indonesia. The subjects of the study were the new cases of pulmonary TB with positive AFB and inactive pulmonary TB who met the inclusion and exclusion criteria. Blood serum was collected and examined to measure neopterin serum levels in patients by ELISA technique.

RESULTS

There was a significant difference of mean neopterin serum levels between the new cases of pulmonary TB with positive AFB and inactive pulmonary TB with a p-value <0.001 (74.92 nmol/l vs. 9.84 nmol/l). There was a significant difference in serum neopterin levels in each AFB grading in the new cases of pulmonary TB with positive AFB with a p-value <0.001 (60.10 nmol/l in AFB 1+, 80.81 nmol/l in AFB 2+, and 110.70 nmol/l in AFB 3+).

CONCLUSION

Serum neopterin levels in the new cases of pulmonary TB with positive AFB were higher than inactive pulmonary TB.

Light emitting diode (LED) based fluorescence microscopy for tuberculosis detection: a review

Since time immemorial, tuberculosis (TB) has intimidated the human race owing to its severity. Its socio-economic burden has led to it being a major cause of concern. It is one of the world's major causes of death from a single agent. Since most of the middle- and low-income countries are burdened with TB, sputum smear examination using conventional light microscopy is often the only resort for diagnosing TB. However, fluorescence microscopy is used as standard in most high-income countries, owing to its increased sensitivity. Light-emitting diodes (LEDs), being inexpensive, are increasingly gaining popularity as an alternative light source for fluorescence microscopy. It has been found to be highly efficient and has a lot of advantages over the conventional Ziehl-Neelsen-based bright field microscopy. In this review, we discuss about the usefulness of LED-based fluorescence microscopy in diagnosing TB and how it is superior to the other sources of light used.

Persistent Mycobacterium tuberculosis infection in mice requires PerM for successful cell division

The ability of Mycobacterium tuberculosis (Mtb) to persist in its host is central to the pathogenesis of tuberculosis, yet the underlying mechanisms remain incompletely defined. PerM, an integral membrane protein, is required for persistence of Mtb in mice. Here, we show that perM deletion caused a cell division defect specifically during the chronic phase of mouse infection, but did not affect Mtb's cell replication during acute infection. We further demonstrate that PerM is required for cell division in chronically infected mice and in vitro under host-relevant stresses because it is part of the mycobacterial divisome and stabilizes the essential divisome protein FtsB. These data highlight the importance of sustained cell division for Mtb persistence, define condition-specific requirements for cell division and reveal that survival of Mtb during chronic infection depends on a persistence divisome.

Analysis of predicted amino acid biosynthesis in Rv3344c in Mycobacterium tuberculosis H37 Rv using bioinformatics tools

According to World Health Organization (WHO) report, Mycobacterium tuberculosis H₃₇ Rv (M. tuberculosis) affects one-third population of the world. Emergence of effective treatment/research against this disease is need of the hour. Therefore, we present some important aspects of Rv3344c, which is a PE_PGRS protein. Evidence shows that PE_PGRS proteins show fibronectin binding activity. This protein has affinity for calcium and also shows motifs of GTP-binding protein. It also shows the presence of sites for ribose-5-phosphate binding and motifs of aspartate-beta-semialdehyde dehydrogenase, both of which are involved in amino acid biosynthesis. Thus, this protein might be targeted to block the amino acid biosynthesis in M. tuberculosis. This article takes into consideration some important aspects of Rv3344c protein as its function is still unknown. This study includes retrieval of protein sequence database, multiple sequence alignment, protein-protein interaction, epitope prediction, localization, function prediction, phosphorylation site prediction, model building and its validation, ligand-binding prediction along with mutational analysis. Hence, this study might be an important step in the development of new drugs and treatment of tuberculosis.

Inhaled Antibiotics for Mycobacterial Lung Disease

Mycobacterial lung diseases are an increasing global health concern. Tuberculosis and nontuberculous mycobacteria differ in disease severity, epidemiology, and treatment strategies, but there are also a number of similarities. Pathophysiology and disease progression appear to be relatively similar between these two clinical diagnoses, and as a result these difficult to treat pulmonary infections often require similarly extensive treatment durations of multiple systemic drugs. In an effort to improve treatment outcomes for all mycobacterial lung diseases, a significant body of research has investigated the use of inhaled antibiotics. This review discusses previous research into inhaled development programs, as well as ongoing research of inhaled therapies for both nontuberculous mycobacterial lung disease, and tuberculosis. Due to the similarities between the causative agents, this review will also discuss the potential cross-fertilization of development programs between these similar-yet-different diseases. Finally, we will discuss some of the perceived difficulties in developing a clinically utilized inhaled antibiotic for mycobacterial diseases, and potential arguments in favor of the approach.

Role of α-glucan-induced oxygen species in dendritic cells and its impact in immune response against tuberculosis

With 10 million new cases and three million deaths estimated to occur yearly ̶ more than any time in history ̶ tuberculosis (TB) remains the single most widespread and deadly infectious disease. Until recently, it was thought that both latent and active TB was primarily related to host factors. Nonetheless, the participation of bacterial factors is becoming increasingly evident. Minimal variations in genes related to Mycobacterium tuberculosis (Mtb) virulence and pathogenesis can lead to marked differences in immunogenicity. Dendritic cells (DC) are professional antigen presenting cells whose maturation can vary depending on the cell wall composition of each particular Mtb strain being critical for the onset of the immune response against Mtb. Here we evaluated the role played by α-glucan, in the endogenous production of reactive oxygen species, ROS, and the impact on DC maturation and function. Results showed that α-glucans on Mtb induce ROS production leading to DC maturation and lymphocyte proliferation. Even more, α-glucans induced Syk activation but were not essential in non-opsonized phagocytosis. In summary, α-glucans of Mtb participates in ROS production and the subsequent DC maturation and antigen presentation, suggesting a relevant role of α-glucans for the onset of the protective immune response against TB.

An overview of new antitubercular drugs, drug candidates, and their targets

The causative agent of tuberculosis (TB), Mycobacterium tuberculosis and more recently totally drug-resistant strains of M. tuberculosis, display unique mechanisms to survive in the host. A four-drug treatment regimen was introduced 40 years ago but the emergence of multidrug-resistance and more recently TDR necessitates the identification of new targets and drugs for the cure of M. tuberculosis infection. The current efforts in the drug development process are insufficient to completely eradicate the TB epidemic. For almost five decades the TB drug development process remained stagnant. The last 10 years have made sudden progress giving some new and highly promising drugs including bedaquiline, delamanid, and pretomanid. Many of the candidates are repurposed compounds, which were developed to treat other infections but later, exhibited anti-TB properties also. Each class of drug has a specific target and a definite mode of action. These targets are either involved in cell wall biosynthesis, protein synthesis, DNA/RNA synthesis, or metabolism. This review discusses recent progress in the discovery of newly developed and Food and Drug Administration approved drugs as well as repurposed drugs, their targets, mode of action, drug-target interactions, and their structure-activity relationship.

Comprehensive Comparative Analysis of Cholesterol Catabolic Genes/Proteins in Mycobacterial Species

In dealing with Mycobacterium tuberculosis, the causative agent of the deadliest human disease—tuberculosis (TB)—utilization of cholesterol as a carbon source indicates the possibility of using cholesterol catabolic genes/proteins as novel drug targets. However, studies on cholesterol catabolism in mycobacterial species are scarce, and the number of mycobacterial species utilizing cholesterol as a carbon source is unknown. The availability of a large number of mycobacterial species’ genomic data affords an opportunity to explore and predict mycobacterial species’ ability to utilize cholesterol employing in silico methods. In this study, comprehensive comparative analysis of cholesterol catabolic genes/proteins in 93 mycobacterial species was achieved by deducing a comprehensive cholesterol catabolic pathway, developing a software tool for extracting homologous protein data and using protein structure and functional data. Based on the presence of cholesterol catabolic homologous proteins proven or predicted to be either essential or specifically required for the growth of M. tuberculosis H37Rv on cholesterol, we predict that among 93 mycobacterial species, 51 species will be able to utilize cholesterol as a carbon source. This study’s predictions need further experimental validation and the results should be taken as a source of information on cholesterol catabolism and genes/proteins involved in this process among mycobacterial species.

Mycobacterial Musculoskeletal Infections

Although less common as causes of musculoskeletal infection than pyogenic bacteria, both Mycobacterium tuberculosis and nontuberculous mycobacteria can infect bones and joints. Although tuberculous arthritis and osteomyelitis have been recognized for millennia, infections caused by nontuberculous mycobacteria are being identified more often, likely because of a more susceptible host population and improvements in diagnostic capabilities. Despite advances in modern medicine, mycobacterial infections of the musculoskeletal system remain particularly challenging to diagnose and manage. This article discusses clinical manifestations of musculoskeletal infections caused by Mycobacterium tuberculosis and nontuberculous mycobacteria. Pathogenesis, unique risk factors, and diagnostic and therapeutic approaches are reviewed.

Expanding the Current Knowledge About the Role of Interleukin-10 to Major Concerning Bacteria

Interleukin-10 (IL-10) is one of the most important anti-inflammatory cytokine produced during bacterial infection. Two related phenomena explain the importance of IL-10 production in this context: first, the wide range of cells able to produce this cytokine and second, the wide effects that it causes on target cells. In a previous report we described opposing roles of IL-10 production during bacterial infection. Overall, during infections caused by intracellular bacteria or by pathogens that modulate the inflammatory response, IL-10 production facilitates bacterial persistence and dissemination within the host. Whereas during infections caused by extracellular or highly inflammatory bacteria, IL-10 production reduces host tissue damage and facilitates host survival. Given that these data were obtained using antibiotic susceptible bacteria, the potential application of these studies to multi-drug resistant (MDR) bacteria needs to be evaluated. MDR bacteria can become by 2050 a major death cause worldwide, not only for its ability to resist antimicrobial therapy but also because the virulence of these strains is different as compared to antibiotic susceptible strains. Therefore, it is important to understand the interaction of MDR-bacteria with the immune system during infection. This review discusses the current data about the role of IL-10 during infections caused by major circulating antibiotic resistant bacteria. We conclude that the production of IL-10 improves host survival during infections caused by extracellular or highly inflammatory bacteria, however, it is detrimental during infections caused by intracellular bacteria or bacterial pathogens that modulate the inflammatory response. Importantly, during MDR-bacterial infections a differential IL-10 production has been described, compared to non-MDR bacteria, which might be due to virulence factors specific of MDR bacteria that modulate production of IL-10. This knowledge is important for the development of new therapies against infections caused by these bacteria, where antibiotics effectiveness is dramatically decreasing.

Characterization of immune responses of human PBMCs infected with Mycobacterium tuberculosis H37Ra: Impact of donor declared BCG vaccination history on immune responses and M. tuberculosis growth

This study characterized the immune responses in early Mycobacterium tuberculosis (Mtb) H37Ra infection of human peripheral blood mononuclear cell (PBMC)-collagen matrix culture and the impact of Bacille Calmette-Guérin (BCG) vaccination history of donor PBMCs on the immune responses to Mtb infection. Aggregates of PBMCs were initially observed on day 3 and the size of aggregates continued to increase on day 8 post-infection, where macrophages and T cell subsets were identified to be present. Similarly, mycobacterial load progressively increased in infected PBMCs during the 8 days of culture but were significantly lower in infected PBMCs from BCG vaccinated (BCG+) donors compared to unvaccinated (BCG-) donors. The levels of INF-γ, TNF-α, IL-4, IL-6, IL-10 and IL-17 in the supernatants of Mtb-infected PBMCs peaked at day 3 and decreased on days 5 and 8. The levels of these cytokines except IL-10 were significantly lower in Mtb-infected PBMCs from BCG+ donors compared to infected PBMCs from BCG- donors. The percentages of activated naïve Th cells, activated effector memory Th cells and activated central memory Tc cells were significantly higher in Mtb-infected PBMCs compared to uninfected PBMCs at day 8 post-infection. Further, the proportion of activated central memory Tc cells was significantly higher in infected PBMCs from BCG+ donors compared to the BCG- donors. This study highlights the possibility that BCG vaccination may confound results that utilize human PBMCs to study Mtb infection.

Fluorescence Imaging of Mycobacterial Infection in Live Mice Using Fluorescent Protein-Expressing Strains

Fluorescence imaging has been applied to various areas of biological research, including studies of physiological, neurological, oncological, cell biological, molecular, developmental, immunological, and infectious processes. In this chapter, we describe methods of fluorescent imaging applied to examination of subcutaneous and pulmonary mycobacterial infections in an animal model. Since slow growth of Mycobacterium tuberculosis (Mtb) hinders development of new diagnostics, therapeutics, and vaccines for tuberculosis (TB), we developed fluorescent protein (FP) expressing mycobacterial strains for in vivo imaging, which can be used to track bacterial location and to quantitate bacterial load directly in living animals. After comparison of imaging data using strains expressing different fluorescent proteins, we found that strains expressing L5-tdTomato display the greatest fluorescence. Here, we describe detailed protocols for tdTomato-labeled M. bovis BCG imaging in real time for subcutaneous and pulmonary infections in living mice. These procedures allow rapid and accurate determination of bacterial numbers in live mice.

Cell envelope lipids in the pathophysiology of Mycobacterium tuberculosis

Mycobacterium tuberculosis is an intracellular bacterium that persists and replicates inside macrophages. The bacterium possesses an unusual lipid-rich cell envelope that provides a hydrophobic impermeable barrier against many environmental stressors and allows it to survive extremely hostile intracellular surroundings. Since the lipid-rich envelope is crucial for M. tuberculosis virulence, the components of the cell wall lipid biogenesis pathways constitute an attractive target for the development of vaccines and antimycobacterial chemotherapeutics. In this review, we provide a detailed description of the mycobacterial cell envelope lipid components and their contributions to the physiology and pathogenicity of mycobacteria. We also discussed the current status of the antimycobacterial drugs that target biosynthesis, export and regulation of cell envelope lipids.

Interventions to increase tuberculosis case detection at primary healthcare or community-level services

BACKGROUND

Pulmonary tuberculosis is usually diagnosed when symptomatic individuals seek care at healthcare facilities, and healthcare workers have a minimal role in promoting the health-seeking behaviour. However, some policy specialists believe the healthcare system could be more active in tuberculosis diagnosis to increase tuberculosis case detection.

OBJECTIVES

To evaluate the effectiveness of different strategies to increase tuberculosis case detection through improving access (geographical, financial, educational) to tuberculosis diagnosis at primary healthcare or community-level services.

SEARCH METHODS

We searched the following databases for relevant studies up to 19 December 2016: the Cochrane Infectious Disease Group Specialized Register; the Cochrane Central Register of Controlled Trials (CENTRAL), published in the Cochrane Library, Issue 12, 2016; MEDLINE; Embase; Science Citation Index Expanded, Social Sciences Citation Index; BIOSIS Previews; and Scopus. We also searched the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP), ClinicalTrials.gov, and the metaRegister of Controlled Trials (mRCT) for ongoing trials.

SELECTION CRITERIA

Randomized and non-randomized controlled studies comparing any intervention that aims to improve access to a tuberculosis diagnosis, with no intervention or an alternative intervention.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for eligibility and risk of bias, and extracted data. We compared interventions using risk ratios (RR) and 95% confidence intervals (CI). We assessed the certainty of the evidence using the GRADE approach.

MAIN RESULTS

We included nine cluster-randomized trials, one individual randomized trial, and seven non-randomized controlled studies. Nine studies were conducted in sub-Saharan Africa (Ethiopia, Nigeria, South Africa, Zambia, and Zimbabwe), six in Asia (Bangladesh, Cambodia, India, Nepal, and Pakistan), and two in South America (Brazil and Colombia); which are all high tuberculosis prevalence areas.Tuberculosis outreach screening, using house-to-house visits, sometimes combined with printed information about going to clinic, may increase tuberculosis case detection (RR 1.24, 95% CI 0.86 to 1.79; 4 trials, 6,458,591 participants in 297 clusters, low-certainty evidence); and probably increases case detection in areas with tuberculosis prevalence of 5% or more (RR 1.52, 95% CI 1.10 to 2.09; 3 trials, 155,918 participants, moderate-certainty evidence; prespecified stratified analysis). These interventions may lower the early default (prior to starting treatment) or default during treatment (RR 0.67, 95% CI 0.47 to 0.96; 3 trials, 849 participants, low-certainty evidence). However, this intervention may have may have little or no effect on treatment success (RR 1.07, 95% CI 1.00 to 1.15; 3 trials, 849 participants, low-certainty evidence), and we do not know if there is an effect on treatment failure or mortality. One study investigated long-term prevalence in the community, but with no clear effect due to imprecision and differences in care between the two groups (RR 1.14, 95% CI 0.65 to 2.00; 1 trial, 556,836 participants, very low-certainty evidence).Four studies examined health promotion activities to encourage people to attend for screening, including mass media strategies and more locally organized activities. There was some increase, but this could have been related to temporal trends, with no corresponding increase in case notifications, and no evidence of an effect on long-term tuberculosis prevalence. Two studies examined the effects of two to six nurse practitioner educational sessions in tuberculosis diagnosis, with no clear effect on tuberculosis cases detected. One trial compared mobile clinics every five days with house-to-house screening every six months, and showed an increase in tuberculosis cases.There was also insufficient evidence to determine if sustained improvements in case detection impact on long-term tuberculosis prevalence; this was evaluated in one study, which indicated little or no effect after four years of either contact tracing, extensive health promotion activities, or both (RR 1.31, 95% CI 0.75 to 2.30; 1 study, 405,788 participants in 12 clusters, very low-certainty evidence).

AUTHORS' CONCLUSIONS

The available evidence demonstrates that when used in appropriate settings, active case-finding approaches may result in increase in tuberculosis case detection in the short term. The effect of active case finding on treatment outcome needs to be further evaluated in sufficiently powered studies.

Calcimycin mediates mycobacterial killing by inducing intracellular calcium-regulated autophagy in a P2RX7 dependent manner

Phenotypic screening led to the identification of calcimycin as a potent inhibitor of Mycobacterium bovis BCG (M. bovis BCG) growth in vitro and in THP-1 cells. In the present study, we aim to decipher the mechanism of antimycobacterial activity of calcimycin. We noticed that treatment with calcimycin led to up-regulation of different autophagy markers like Beclin-1, autophagy-related gene (Atg) 7, Atg 3 and enhanced microtubule-associated protein 1A/1B-light chain 3-I (LC3-I) to LC3-II conversion in macrophages. This calcimycin-mediated killing of intracellular M. smegmatis and M. bovis BCG was abrogated in the presence of 3-methyladenine (3-MA). We also demonstrate that calcimycin binding with purinergic receptor P2X7 (P2RX7) led to increase in intracellular calcium level that regulates the extracellular release of ATP. ATP was able to regulate calcimycin-induced autophagy through P2RX7 in an autocrine fashion. Blocking of either P2RX7 expression by 1-[N,O-bis(5-Isoquinolinesulfonyl)-N-methyl-l-tyrosyl]-4-phenylpiperazine (KN-62) or reducing intracellular calcium levels by 1,2-Bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetra (acetoxy-methyl) ester (BAPTA-AM) abrogated the antimycobacterial activity of calcimycin. Taken together, these results showed that calcimycin exerts its antimycobacterial effect by regulating intracellular calcium-dependent ATP release that induces autophagy in a P2RX7 dependent manner.

In Silico Drug Design of Thiolactomycin Derivatives Against Mtb-KasA Enzyme to Inhibit Multidrug Resistance of Mycobacterium tuberculosis

Tuberculosis (TB) is a leading infectious disease which kills a huge number of people every year over a decade, caused by Mycobacterium tuberculosis. The conventional drugs in the market are no longer effective due to the increasing mycobacterial resistance to antibiotics. Hence, the need of finding efficient drugs to solve this multiple drug resistant factor is becoming an immediate issue. The first-line drugs in current practice for the treatment of TB emphasize on mycolic acid, which protects the bacteria from an immune response generated by the host. A key enzyme involved in this mycolic acid biosynthesis, M. tuberculosis beta-ketoacyl-ACP synthase A (MTB-KasA) is a prime candidate in this study. Thiolactomycin is a natural product inhibitor has shown good inhibitory activity against MTB-KasA. Hence, several thiolactomycin derivatives collected from the literature were taken for absorption, distribution, metabolism, excretion and toxicity prediction, molecular docking and molecular dynamics simulation studies with MTB-KasA. The in silico drug designing methods used in this study suggests that the thiolactomycin derivatives are having a better binding activity against MTB-KasA and among them the ligand C14 is identified as a promising lead molecule to inhibit multidrug resistance of tuberculosis by showing a long time binding activity.

Early diagnosis and effective treatment regimens are the keys to tackle antimicrobial resistance in tuberculosis (TB): A report from Euroscicon's international TB Summit 2016

To say that tuberculosis (TB) has regained a strong foothold in the global human health and wellbeing scenario would be an understatement. Ranking alongside HIV/AIDS as the top reason for mortality due to a single infectious disease, the impact of TB extends far into socio-economic context worldwide. As global efforts led by experts and political bodies converge to mitigate the predicted outcome of growing antimicrobial resistance, the academic community of students, practitioners and researchers have mobilised to develop integrated, inter-disciplinary programmes to bring the plans of the former to fruition. Enabling this crucial requirement for unimpeded dissemination of scientific discovery was the TB Summit 2016, held in London, United Kingdom. This report critically discusses the recent breakthroughs made in diagnostics and treatment while bringing to light the major hurdles in the control of the disease as discussed in the course of the 3-day international event. Conferences and symposia such as these are the breeding grounds for successful local and global collaborations and therefore must be supported to expand the understanding and outreach of basic science research.