Mycobacterium tuberculosis Dissemination Plays a Critical Role in Pathogenesis

Stimulated expression of ELR+ chemokines, VEGFA and TNF-AIP3 promote mycobacterial dissemination in extrapulmonary tuberculosis patients and Cavia porcellus model of tuberculosis

Pathogenic mycobacteria induce and accelerate blood vessel formation driven by extensive inflammation during granuloma formation, which is a central feature of mycobacterial pathogenesis. Tumor necrosis factor-alpha (TNF-α) enhances the expression of vascular endothelial growth factor (VEGF) and glutamic acid-leucine-arginine (ELR+) chemokines, which are potent inducers of vascularization. Most of the reported research work contends that VEGF growth factor induces neovascularization in human tuberculosis (TB) patients, but the evidence is inconclusive. Considerable ambiguity exists concerning the factors responsible for miliary tuberculosis. To identify such factors, we proposed an alternative explanation that could be found in miliary tuberculosis (MTB) cases. We performed a comparative analysis of angiogenic factors TNF-α, VEGF, and angiogenic ELR+ CXC and CC chemokine ligands in extrapulmonary tuberculosis (EPTB) and pulmonary tuberculosis (PTB) patients. To observe the relationship of these factors with the severity of bacterial burden, guinea pigs were infected with Mycobacterium tuberculosis (M.tb) and levels of the angiogenic factors were examined at different time intervals. Expression of these factors also exhibited a significant positive correlation with bacterial burden in other organs like the spleen, liver, and lymph nodes. We demonstrated statistical data on bacterial burden at different time points following the dissemination of infection in guinea pigs. In this study, we observed that there was a stimulated increase in the expression of ELR+ chemokines and VEGF in EPTB patients as compared to PTB patients. Following increased dissemination, the host immune response clears bacteria from the lungs during disease progression in guinea pigs.

Cyclic-di-AMP Phosphodiesterase Elicits Protective Immune Responses Against Mycobacterium tuberculosis H37Ra Infection in Mice

Many antigens from Mycobacterium tuberculosis (M. tuberculosis) have been demonstrated as strong immunogens and proved to have application potential as vaccine candidate antigens. Cyclic di-AMP (c-di-AMP) as a bacterial second messenger regulates various bacterial processes as well as the host immune responses. Rv2837c, the c-di-AMP phosphodiesterase (CnpB), was found to be relative to virulence of M. tuberculosis and interference with host innate immune response. In this study, recombinant CnpB was administered subcutaneously to mice. We found that CnpB had strong immunogenicity and induced high levels of humoral response and lung mucosal immunity after M. tuberculosis intranasally infection. CnpB immunization stimulated splenocyte proliferation and the increasing number of activated NK cells but had little effects on Th1/Th2 cellular immune responses in spleens. However, CnpB induced significant Th1/Th2 cellular immune responses with a decreased number of T and B cells in the lungs, and significantly recruits of CD4+ and CD8+ T cells after M. tuberculosis attenuated strain H37Ra infection. Besides, we first reported that CnpB could stimulate IFN-β expression transitorily and inhibit the autophagy of macrophages in vitro. In mice intranasally infection model, CnpB immunization alleviated pathological changes and reduced M. tuberculosis H37Ra loads in the lungs. Thus, our results suggested that CnpB interferes with host innate and adaptive immune responses and confers protection against M. tuberculosis respiratory infection, which should be considered in vaccine development as well as a drug target.

Diagnosis of Mycobacterium tuberculosis using GeneXpert MTB / RIF and TB-LAMP techniques from pulmonary and extra-pulmonary TB patients in Iraq

Tuberculosis is considered one globally public health problem, particularly in unindustrialized countries. The disease has an increasing threat to public health, causing high morbidity and mortality rates. So, rapid diagnosis is critical to diminish the death and interfere with transmission. In this study, GeneXpert MTB/RIF and Loop-Mediated Isothermal Amplification (TB-LAMP) assays were utilized for the rapid molecular diagnosis of Mycobacterium tuberculosis bacteria and compared sensitivity and specificity of Mycobacterium tuberculosis bacteria; these tests with acid-fast bacilli staining in pulmonary and extra-pulmonary clinical specimens from Iraqi patients in Baghdad capital. 141 pulmonary and extra-pulmonary samples were collected and tested for tuberculosis detection. Acid-fast bacilli, TB-LAMP and GeneXpert MTB/RIF methods were used to diagnose tuberculosis. Of 141 tuberculosis specimens, 58 were acid-fast bacilli smear-positive, while 90 samples were positive for Mycobacterium tuberculosis by GeneXpert MTB/RIF assay and 78 by TB-LAMP assay. The results reported a high sensitivity rate of GeneXpert MTB/RIF assay compared to the TB-LAMP and bacilli staining method. The sensitivity of GeneXpert was 63.83%, specificity 50%; positive and negative predictive values were 58.36% to 68.96% and 42.73% to 57.27%, respectively. TB-LAMP sensitivity was 55.32%, specificity 50%; positive and negative predictive values were 49.61% to 60.89% and 43.70% to 56.30%, respectively, while the sensitivity of bacilli staining was 41.13%, specificity 50%; positive and negative predictive values were 35.26% to 47.27% and 44.88% to 55.12%, respectively, these values are dependent on disease prevalence. We concluded that the GeneXpert MTB/RIF test is more sensitive and specific than the TB-LAMP and both techniques are more sensitive and specific than the conventional acid-fast staining method for both pulmonary and extra-pulmonary specimens. Despite culture remaining the gold standard for laboratory confirmation of TB, GeneXpert MTB/RIF and TB-LAMP should become standard practice for patients with suspected TB, and all clinicians and public health programs for TB control should have access to molecular testing for TB to shorten diagnosis time. Keywords. Mycobacterium tuberculosis; Pulmonary TB; Extrapulmonary TB; GeneXpert MTB/RIF; TB-LAMP; A.F.B

Direct Attachment with Erythrocytes Augments Extracellular Growth of Pathogenic Mycobacteria

Pathogenic intracellular mycobacteria, such as Mycobacterium tuberculosis and Mycobacterium avium, which cause lung diseases, can grow in macrophages. Extracellular mycobacteria have been reported in the lungs, blood, and sputum of patients, indicating the involvement of these pathogens in disease progression. Erythrocytes are involved in the symptoms associated with pulmonary mycobacterial diseases, such as bloody sputum and hemoptysis; however, little attention has been paid to the role of erythrocytes in mycobacterial diseases. Herein, we found that Mycobacterium avium subsp. hominissuis (MAH) and Mycobacterium intracellulare colocalized with erythrocytes at the sites of lung infection, inside capillaries and necrotic areas of granulomas, using histopathological examinations. Electron microscopy showed that MAH adhered and entered human erythrocytes when they were cocultured in vitro. MAH adhered to erythrocytes through complement receptor 1 and cell-surface sialo-glycoproteins. Importantly, MAH grew vigorously without causing any pronounced damage to erythrocytes. This erythrocyte-mediated enhancement of MAH growth occurred extracellularly depending on its direct attachment to erythrocytes. In contrast, MAH failed to multiply inside erythrocytes. Similarly, erythrocytes augmented the growth of other pathogenic mycobacteria, such as M. intracellulare and M. tuberculosis. THP-1 cell-derived human macrophages preferentially phagocytosed erythrocytes that were attached to mycobacteria (compared to bacteria alone), suggesting that erythrocyte-attached mycobacteria are an efficient infectious source for macrophages. Our findings provide new insights into the pathogenesis of mycobacterial diseases and offer an alternative and useful strategy for treating mycobacterial disease. IMPORTANCE Pathogenic mycobacteria, such as Mycobacterium tuberculosis, Mycobacterium avium subsp. hominissuis (MAH), and Mycobacterium intracellulare, cause pulmonary infections as intracellular parasites of lung macrophages and epithelial cells. Here, using histopathological examinations we found that MAH and M. intracellulare colocalized with erythrocytes in lung infection sites. Subsequent studies demonstrated that direct interaction with erythrocytes enhances the extracellular proliferation of mycobacteria based on the following results: 1. MAH adhered and invaded human erythrocytes upon coculture in vitro; 2. MAH adhered to erythrocytes through complement receptor 1 and cell-surface sialo-glycoproteins; 3. MAH rapidly proliferated when directly attached to erythrocytes but not within them; 4. other mycobacteria, such as M. intracellulare and M. tuberculosis, also proliferated in the same way as MAH. The finding that pathogenic mycobacteria grow extracellularly in an erythrocyte-dependent manner is of considerable clinical importance for understanding disease progression and latent infection.

Diverse Cell Death Mechanisms Are Simultaneously Activated in Macrophages Infected by Virulent Mycobacterium tuberculosis

Macrophages are necessary to eliminate pathogens. However, some pathogens have developed mechanisms to avoid the immune response. One of them is modulating the cell death mechanism to favor pathogen survival. In this study, we evaluated if virulent Mycobacterium tuberculosis (M. tb) can simultaneously activate more than one cell death mechanism. We infected human monocyte-derived macrophages (MDM) in vitro with avirulent (H37Ra) and virulent (H37Rv) strains, and then we measured molecules involved in apoptosis, necroptosis, and pyroptosis. Our data showed that H37Rv infection increased the BCL-2 transcript and protein, decreased the BAX transcript, and increased phosphorylated BCL-2 at the protein level. Moreover, H37Rv infection increased the expression of the molecules involved in the necroptotic pathway, such as ASK1, p-38, RIPK1, RIPK3, and caspase-8, while H37Ra increased caspase-8 and decreased RIPK3 at the transcriptional level. In addition, NLRP3 and CASP1 expression was increased at low MOI in both strains, while IL-1β was independent of virulence but dependent on infection MOI, suggesting the activation of pyroptosis. These findings suggest that virulent M. tb inhibits the apoptosis mediated by BCL-2 family molecules but, at the same time, increases the expression of molecules involved in apoptosis, necroptosis, and pyroptosis at the transcriptional and protein levels, probably as a mechanism to avoid the immune response and guarantee its survival.

Neutrophil-Mediated Immunopathology and Matrix Metalloproteinases in Central Nervous System - Tuberculosis

Tuberculosis (TB) remains one of the leading infectious killers in the world, infecting approximately a quarter of the world’s population with the causative organism Mycobacterium tuberculosis (M. tb). Central nervous system tuberculosis (CNS-TB) is the most severe form of TB, with high mortality and residual neurological sequelae even with effective TB treatment. In CNS-TB, recruited neutrophils infiltrate into the brain to carry out its antimicrobial functions of degranulation, phagocytosis and NETosis. However, neutrophils also mediate inflammation, tissue destruction and immunopathology in the CNS. Neutrophils release key mediators including matrix metalloproteinase (MMPs) which degrade brain extracellular matrix (ECM), tumor necrosis factor (TNF)-α which may drive inflammation, reactive oxygen species (ROS) that drive cellular necrosis and neutrophil extracellular traps (NETs), interacting with platelets to form thrombi that may lead to ischemic stroke. Host-directed therapies (HDTs) targeting these key mediators are potentially exciting, but currently remain of unproven effectiveness. This article reviews the key role of neutrophils and neutrophil-derived mediators in driving CNS-TB immunopathology.

Detection of Mycobacterium tuberculosis complex DNA in oronasal swabs from infected African buffaloes (Syncerus caffer)

Mycobacterium bovis (M. bovis), a member of the Mycobacterium tuberculosis complex (MTBC), is the causative agent of bovine TB (bTB) in animals. Spread occurs through inhalation or ingestion of bacilli transmitted from infected individuals. Early and accurate detection of infected African buffaloes shedding M. bovis is essential for interrupting transmission. In this pilot study, we determined if MTBC DNA could be detected in M. bovis infected buffalo oronasal secretions using a molecular transport media (PrimeStore MTM) with oronasal swabs and a rapid qPCR assay (Xpert MTB/RIF Ultra). Bovine TB test-positive buffaloes were culled, then tissue samples and oronasal swabs collected post-mortem for mycobacterial culture and Ultra testing, respectively. The Ultra detected MTBC DNA in 5/12 swabs from M. bovis culture-confirmed buffaloes. Oronasal swabs from M. bovis negative buffaloes (n = 20) were negative on Ultra, indicating the high specificity of this test. This study showed that MTM can successfully preserve MTBC DNA in oronasal swabs. The proportion of MTBC positive oronasal swabs was higher than expected and suggests that the Ultra may be an additional method for identifying infected buffaloes. Further studies are needed to confirm the utility of the Ultra assay with oronasal swabs as an assay to evaluate possible MTBC shedding in buffaloes.

Machine learning analysis of SERS fingerprinting for the rapid determination of Mycobacterium tuberculosis infection and drug resistance

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Handheld Raman spectrometer is able to generate SERS spectra with sufficient quality for Mycobacterium tuberculosis detection.

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It is feasible to accurately discriminate Mtb-positive sputum from Mtb-negative sputum through SERS spectrometry.

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Pulmonary and extra-pulmonary Mtb strains were able to be accurately distinguished via SERS spectral analysis.

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Profiling of antibiotic resistance of Mtb strains was successfully achieved through machine learning analysis of SERS spectra.

Over the past decades, conventional methods and molecular assays have been developed for the detection of tuberculosis (TB). However, these techniques suffer limitations in the identification of Mycobacterium tuberculosis (Mtb), such as long turnaround time and low detection sensitivity, etc., not even mentioning the difficulty in discriminating antibiotics-resistant Mtb strains that cause great challenges in TB treatment and prevention. Thus, techniques with easy implementation for rapid diagnosis of Mtb infection are in high demand for routine TB diagnosis. Due to the label-free, low-cost and non-invasive features, surface enhanced Raman spectroscopy (SERS) has been extensively investigated for its potential in bacterial pathogen identification. However, at current stage, few studies have recruited handheld Raman spectrometer to discriminate sputum samples with or without Mtb, separate pulmonary Mtb strains from extra-pulmonary Mtb strains, or profile Mtb strains with different antibiotic resistance characteristics. In this study, we recruited a set of supervised machine learning algorithms to dissect different SERS spectra generated via a handheld Raman spectrometer with a focus on deep learning algorithms, through which sputum samples with or without Mtb strains were successfully differentiated (5-fold cross-validation accuracy = 94.32%). Meanwhile, Mtb strains isolated from pulmonary and extra-pulmonary samples were effectively separated (5-fold cross-validation accuracy = 99.86%). Moreover, Mtb strains with different drug-resistant profiles were also competently distinguished (5-fold cross-validation accuracy = 99.59%). Taken together, we concluded that, with the assistance of deep learning algorithms, handheld Raman spectrometer has a high application potential for rapid point-of-care diagnosis of Mtb infections in future.

Unbalanced serum immunoglobulins in clinical subtypes of pediatric tuberculosis disease

Immune response to tuberculosis (TB) has been extensively studied in the past decades and classically involves cellular immunity. However, evidence suggests that humoral immunity may play a relevant role. Past studies regarding serum immunoglobulin (Ig) levels in TB are dated and only involve adult subjects. In this study, we retrospectively studied a cohort of 256 children with TB disease and analyzed 111 patients screened for total serum Ig at diagnosis. According to the severity and extent of organ involvement, subjects were divided into four groups, namely, uncomplicated pulmonary TB (UCPTB, 56.3% of patients), complicated pulmonary TB (CPTB, 22.5%), lymph node extrapulmonary TB (LN-EPTB, 7.2%), and extra-nodal extrapulmonary TB (EN-EPTB, 13.5%). Serum IgG and IgA levels were significantly higher in more severe and extended TB disease. Median IgG levels progressively increased from uncomplicated to complicated pulmonary and nodal forms, reaching their highest values in diffuse extra-pulmonary TB. In parallel, UCPTB showed significantly lower frequencies of patients presenting a substantial increase in IgG levels when compared with the other three groups. No relevant differences in IgM levels were detected. Ig screening at follow-up showed a significant reduction in IgG and IgA levels. Finally, we unveiled three cases of selective IgA and one case of selective IgM deficiencies (SIgMD), the latter with a severe clinical course. Serum IgG and IgA may be a useful clinical tool to assess the severity and monitor the treatment response in pediatric TB disease. Moreover, immunological workup in children with TB disease may unmask primary defects of humoral immunity.

Idiosyncratic Biogenesis of Intracellular Pathogens-Containing Vacuoles

While most bacterial species taken up by macrophages are degraded through processing of the bacteria-containing vacuole through the endosomal-lysosomal degradation pathway, intravacuolar pathogens have evolved to evade degradation through the endosomal-lysosomal pathway. All intra-vacuolar pathogens possess specialized secretion systems (T3SS-T7SS) that inject effector proteins into the host cell cytosol to modulate myriad of host cell processes and remodel their vacuoles into proliferative niches. Although intravacuolar pathogens utilize similar secretion systems to interfere with their vacuole biogenesis, each pathogen has evolved a unique toolbox of protein effectors injected into the host cell to interact with, and modulate, distinct host cell targets. Thus, intravacuolar pathogens have evolved clear idiosyncrasies in their interference with their vacuole biogenesis to generate a unique intravacuolar niche suitable for their own proliferation. While there has been a quantum leap in our knowledge of modulation of phagosome biogenesis by intravacuolar pathogens, the detailed biochemical and cellular processes affected remain to be deciphered. Here we discuss how the intravacuolar bacterial pathogens Salmonella, Chlamydia, Mycobacteria, Legionella, Brucella, Coxiella, and Anaplasma utilize their unique set of effectors injected into the host cell to interfere with endocytic, exocytic, and ER-to-Golgi vesicle traffic. However, Coxiella is the main exception for a bacterial pathogen that proliferates within the hydrolytic lysosomal compartment, but its T4SS is essential for adaptation and proliferation within the lysosomal-like vacuole.

Angioplasty With Stent Implantation for Portal Venous Stenosis Caused by Abdominal Tuberculosis: A Case Report and Literature Review

Abdominal tuberculosis is one of common forms of extra-pulmonary tuberculosis. However, portal vein involvement leading to portal venous stenosis and portal hypertension is a rare complication in abdominal tuberculosis. Because of the non-specific presentations and insensitive response to anti-tuberculosis therapy of the lesions involving portal vein, it continues to be both a diagnostic and treatment challenge. We have reported a 22-year-old woman presented with massive ascites and pleural effusion, which was proved to be TB infection by pleural biopsy. After standard anti-tuberculosis therapy, her systemic symptoms completely resolved while ascites worsened with serum-ascites albumin gradient >11 g/L. Contrast-enhanced computed tomography and portal venography showed severe main portal vein stenosis from compression by multiple calcified hilar lymph nodes. Finally, the patient was diagnosed with portal venous stenosis due to lymphadenopathy after abdominal tuberculosis infection. Portal venous angioplasty by balloon dilation with stent implantation was performed and continued anti-tuberculosis therapy were administrated after discharge. The ascites resolved promptly with no recurrence occurred during the six-month follow-up. Refractory ascites due to portal venous stenosis is an uncommon vascular complication of abdominal tuberculosis. Portal venous angioplasty with stent placement could be a safe and effective treatment for irreversible vascular lesions after anti-tuberculosis therapy.

Is Mycobacterium tuberculosis carcinogenic to humans?

We highlight the ability of the tuberculosis (TB) causing bacterial pathogen, Mycobacterium tuberculosis (Mtb), to induce key characteristics that are associated with established IARC classified Group 1 and Group 2A carcinogenic agents. There is sufficient evidence from epidemiological case-control, cohort and meta-analysis studies of increased lung cancer (LC) risk in pre-existing/active/old TB cases. Similar to carcinogens and other pathogenic infectious agents, exposure to aerosol-containing Mtb sprays in mice produce malignant transformation of cells that result in squamous cell carcinoma. Convincing, mechanistic data show several characteristics shared between TB and LC which include chronic inflammation, genomic instability and replicative immortality, just to name a few cancer hallmarks. These hallmarks of cancer may serve as precursors to malignant transformation. Together, these findings form the basis of our postulate that Mtb is a complete human pulmonary carcinogen. We also discuss how Mtb may act as both an initiating agent and promoter of tumor growth. Forthcoming experimental studies will not only serve as proof-of-concept but will also pivot our understanding of how to manage/treat TB cases as well as offer solutions to clinical conundrums of TB lesions masquerading as tumors. Clinical validation of our concept may also help pave the way for next generation personalized medicine for the management of pulmonary TB/cancer particularly for cases that are not responding well to conventional chemotherapy or TB drugs.

Features of the pathogenetic mechanisms of tuberculous peritonitis in an experiment

The prevalence of tuberculous peritonitis that has been observed in the recent decades is the result of lymphohematogenous spread of Mycobacterium tuberculosis (MBT) from lungs and other extrapulmonary sources. It is still unclear why certain organs and anatomical regions get involved in the inflammatory process during generalization of the tuberculosis infection. Why do some cases develop into peritoneal tuberculosis and other into kidney tuberculosis? Thus study aimed to investigate the pathogenesis of tuberculous peritonitis in a reproducible biological model. Tuberculous peritonitis was modeled in 18 rabbits (10 in the test group, 8 in control) by intraperitoneal inoculation of the MBT suspension. In order to suppress peritoneal macrophages and major cytokines, test group rabbits were injected with the TNFα inhibitor and iron (III) hydroxide sucrose complex before being infected, while control group rabbits received no immunosuppressive drugs. Autopsy of the control group animals revealed changes characteristic of pulmonary tuberculosis in 37.5% of cases, with no damage to other organs and systems registered. Conversely, test group rabbits had the signs of tuberculous peritonitis in their abdominal cavities. The results of this study suggest that it is the local immunity of an anatomical area that largely determines whether a secondary focus of extrapulmonary tuberculosis infection will develop there or not. For the peritoneum, a smaller pool of peritoneal macrophages and weaker cytokine production is a necessary and sufficient condition to have tuberculous peritonitis developing therein.

Gastrointestinal tuberculosis: A systematic review of epidemiology, presentation, diagnosis and treatment

Tuberculosis (TB) once considered a disease of the developing world is infrequent in the developing world too. Its worldwide prevalence with a huge impact on the healthcare system both in economic and health terms has prompted the World Health Organization to make it a top priority infectious disease. Tuberculous infection of the pulmonary system is the most common form of this disease, however, extrapulmonary TB is being increasingly recognized and more often seen in immunocompromised situations. Gastrointestinal TB is a leading extrapulmonary TB manifestation that can defy diagnosis. Overlap of symptoms with other gastrointestinal diseases and limited accuracy of diagnostic tests demands more awareness of this disease. Untreated gastrointestinal TB can cause significant morbidity leading to prolonged hospitalization and surgery. Prompt diagnosis with early initiation of therapy can avoid this. This timely review discusses the epidemiology, risk factors, pathogenesis, clinical presentation, current diagnostic tools and therapy.

Ossified diagnosis: sarcoidosis masquerading as metastatic breast cancer

A 40-year-old woman was referred to the Breast Unit with a solid lump in her right breast. Investigations revealed an invasive lobular carcinoma. The patient underwent a right-sided mastectomy and sentinel lymph node (LN) biopsy, which confirmed axillary LN involvement. The postsurgery staging CT showed unusual enlargement of mediastinal and hilar LN bilaterally. This was consistent with positron emission tomography/CT and MRI, which further established the presence of several bone lesions. Determining the pathology within the LN and bones was pivotal in providing an accurate diagnosis and deciding subsequent management. However, histopathological analysis of the initial endobronchial ultrasound-guided fine-needle aspiration biopsy of mediastinal LN failed to identify definitive metastatic breast cancer cells. The case was extensively discussed in several multidisciplinary team meetings. Collective evidence, including clinical presentation, comparative imaging analysis, and further biopsies confirmed sarcoidosis with bone involvement-mimicking metastatic disease.

Antibacterial activity of a new monocarbonyl analog of curcumin MAC 4 is associated with divisome disruption

Curcumin (CUR) is a symmetrical dicarbonyl compound with antibacterial activity. On the other hand, pharmacokinetic and chemical stability limitations hinder its therapeutic application. Monocarbonyl analogs of curcumin (MACs) have been shown to overcome these barriers. We synthesized and investigated the antibacterial activity of a series of unsymmetrical MACs derived from acetone against Mycobacterium tuberculosis and Gram-negative and Gram-positive species. Phenolic MACs 4, 6 and 8 showed a broad spectrum and potent activity, mainly against M. tuberculosis, Acinetobacter baumannii and methicillin-resistant Staphylococcus aureus (MRSA), with MIC (minimum inhibitory concentration) values ranging from 0.9 to 15.6 µg/mL. The investigation regarding toxicity on human lung cells (MRC-5 and A549 lines) revealed MAC 4 was more selective than MACs 6 and 8, with SI (selectivity index) values ranging from 5.4 to 15.6. In addition, MAC 4 did not demonstrate genotoxic effects on A549 cells and it was more stable than CUR in phosphate buffer (pH 7.4) for 24 h at 37 °C. Fluorescence and phase contrast microscopies indicated that MAC 4 has the ability to disrupt the divisome of Bacillus subtilis without damaging its cytoplasmic membrane. However, biochemical investigations demonstrated that MAC 4 did not affect the GTPase activity of B. subtilis FtsZ, which is the main constituent of the bacterial divisome. These results corroborated that MAC 4 is a promising antitubercular and antibacterial agent.

Insights into the molecular pathogenesis of ocular tuberculosis

Unclear pathogenic mechanisms underlying the ocular tuberculosis (OTB) has resulted in perplexity related to the diagnosis and management of the disease. Developments in experimental research and innovations in molecular diagnostics have recently provided a new understanding of disease pathogenesis and natural history. The current review focuses on the new insights into OTB pathogenesis, derived from in vivo and in vitro studies on Mycobacterium tuberculosis dissemination and localization into the eye, in combination with histopathological studies on chorioretinal tissue and vascular network. Advances in the knowledge of OTB have influenced disease management in the clinical setting and lead to reconsideration of the role of existing treatments and suggesting potential new therapeutic approaches.

Asap1 Affects the Susceptibility of Zebrafish to Mycobacterium by Regulating Macrophage Migration

The ADP ribosylation factor (ARF) GTPase activation protein ASAP1 possesses multiple biological functions, including regulation of cytoskeletal dynamics, small GTP-binding protein receptor recycling, and intracellular vesicle trafficking. Recently, ASAP1 polymorphisms have been reported to be associated with human susceptibility to tuberculosis (TB) according to a large-scale genome-wide association study (GWAS); ASAP1 expression affects dendritic cell migration, which may be involved in TB predisposition. However, it remains unclear whether ASAP1 affects TB in vivo. To address this issue, we used zebrafish as a model system to examine the effects of Asap1 against Mycobacterium marinum, an organism closely related to Mycobacterium tuberculosis. Two zebrafish asap1 homologs (asap1a and asap1b) were identified and characterized. By morpholino knockdown of asap1a and asap1b as a whole, we found that the asap1 morphants showed a higher mycobacterial load than the controls, which was almost rescued by injecting asap1 mRNA that confers resistance to mycobacterial infection. These Asap1-depleted zebrafish also exhibited decreased macrophage migration in response to tail injury or upon infection with M. marinum in the hindbrain ventricle, which was also proved in THP1-derived macrophages of knockdown ASAP1. Together, these findings represent a new perspective on the role of Asap1 in resistance to mycobacterial infection.