Tuberculosis diagnostics in 2015: landscape, priorities, needs, and prospects

The future in diagnostic tools for TB outbreaks: A review of the approaches with focus on LAMP and RPA diagnostics tests

Tuberculosis (TB) is still the most frequent cause of morbidity and mortality in the world caused by Mycobacterium tuberculosis (MTB). Due to slow diagnostic and treatment options, the disease is a major concern for public health and also increases the burden on the global economy. Rapid, sensitive, and cheaper TB diagnosis test is urgent to lower their rates by point of care testing (POCT). Therefore, molecular detection techniques like recombinase polymerase assay (RPA) and Loop-mediated isothermal amplification (LAMP) play a significant role in this regard as they work on the principle of isothermal nucleic acid amplification. RPA and LAMP bridge the research gap between the previous PCR-based detection tool and other reported isothermal tools for MTB. In this review, we endeavor to provide an overview of the assay that will be a novel approach toward a rapid amplification and visualization of DNA by the naked eye in natural light. RPA and LAMP can prove to be a highly specific pathogen detection technique in combination with lateral flow (LF) strips and SYBR Green I. Optimization of amplification conditions also made the assay ideally suited to the resource-limited field application at POCT. Additionally, RPA and LAMP have paved the way for meeting a key component of the POC diagnosis of TB like universal drug susceptibility testing. However, RPA is more suitable at the POC level than LPA as it requires a lower amplification temperature of around 37-42 °C and a simpler primer design.

Examining Diagnostic Efficacy: GeneXpert Versus Traditional Staining Techniques With Culture in the Diagnosis of Tuberculosis

Introduction The tuberculosis (TB) diagnosis involves various methods, such as microscopic examination, culture-based methods, molecular techniques, chest X-rays, serological tests, and interferon-gamma release assays. These methods help identify and confirm TB and its resistance to rifampicin, balancing speed and accuracy for prompt treatment initiation and effective disease management. Aims and objectives To assess the diagnostic accuracy of GeneXpert, Ziehl-Neelsen staining, and fluorescence staining compared to culture media in TB-suspected patients. Materials and methods We analysed 416 patient samples for TB over one year using GeneXpert, Ziehl-Neelsen staining, fluorescence staining, and Löwenstein-Jensen (LJ) medium. Only samples with a suspicion of TB were included in the study. The samples received without clinical history and requests for all four tests were excluded. Results A total of 416 patient samples were categorised into pulmonary and extrapulmonary samples. GeneXpert detected 62 positive cases for TB, out of which 53 were rifampicin-sensitive, seven were rifampicin-indeterminate, and two were rifampicin-resistant. The indeterminate samples were further evaluated using the line probe assay (LPA), of which six were rifampicin-sensitive, and one was rifampicin-resistant. Fluorescent staining detected 44 cases, Ziehl-Neelsen staining detected 40 cases, and LJ culture medium detected 65 cases. Conclusion GeneXpert is superior to staining methods for detecting TB. GeneXpert, combined with microscopy and culture, can enhance TB and multi-drug resistant tuberculosis (MDR-TB) detection and aid in early treatment initiation.

Identification of Mycobacterium tuberculosis Resistance to Common Antibiotics: An Overview of Current Methods and Techniques

Multidrug-resistant tuberculosis (MDR-TB) is an essential cause of tuberculosis treatment failure and death of tuberculosis patients. The rapid and reliable profiling of Mycobacterium tuberculosis (MTB) drug resistance in the early stage is a critical research area for public health. Then, most traditional approaches for detecting MTB are time-consuming and costly, leading to the inappropriate therapeutic schedule resting on the ambiguous information of MTB drug resistance, increasing patient economic burden, morbidity, and mortality. Therefore, novel diagnosis methods are frequently required to meet the emerging challenges of MTB drug resistance distinguish. Considering the difficulty in treating MDR-TB, it is urgently required for the development of rapid and accurate methods in the identification of drug resistance profiles of MTB in clinical diagnosis. This review discussed recent advances in MTB drug resistance detection, focusing on developing emerging approaches and their applications in tangled clinical situations. In particular, a brief overview of antibiotic resistance to MTB was present, referred to as intrinsic bacterial resistance, consisting of cell wall barriers and efflux pumping action and acquired resistance caused by genetic mutations. Then, different drug susceptibility test (DST) methods were described, including phenotype DST, genotype DST and novel DST methods. The phenotype DST includes nitrate reductase assay, RocheTM solid ratio method, and liquid culture method and genotype DST includes fluorescent PCR, GeneXpert, PCR reverse dot hybridization, ddPCR, next-generation sequencing and gene chips. Then, novel DST methods were described, including metabolism testing, cell-free DNA probe, CRISPR assay, and spectral analysis technique. The limitations, challenges, and perspectives of different techniques for drug resistance are also discussed. These methods significantly improve the detection sensitivity and accuracy of multidrug-resistant tuberculosis (MRT) and can effectively curb the incidence of drug-resistant tuberculosis and accelerate the process of tuberculosis eradication.

Exploring the Role of Extracellular Vesicles in the Pathogenesis of Tuberculosis

Tuberculosis (TB) remains a significant global health concern, necessitating accurate diagnosis and treatment monitoring. Extracellular vesicles (EVs), including exosomes, play crucial roles in disease progression, with their associated genes serving as potential biomarkers and therapeutic targets. Leveraging publicly available RNA-Seq datasets of TB patients and healthy controls (HCs), to identify differentially expressed genes (DEGs) and their associated protein-protein interaction networks and immune cell profiles, the common EV-related DEGs were identified and validated in the GSE42830 and GSE40553 datasets. We have identified nine common EV-related DEGs (SERPINA1, TNFAIP6, MAPK14, STAT1, ITGA2B, VAMP5, CTSL, CEACAM1, and PLAUR) upregulated in TB patients. Immune cell infiltration analysis revealed significant differences between TB patients and HCs, highlighting increased proportions of various immune cells in TB patients. These DEGs are involved in crucial cellular processes and pathways related to exocytosis and immune response regulation. Notably, VAMP5 exhibited excellent diagnostic performance (AUC-0.993, sensitivity-93.8%, specificity-100%), with potential as a novel biomarker for TB. The EV-related genes can serve as novel potential biomarkers that can distinguish between TB and HCs. VAMP5, which functions in exosome biogenesis and showed significant upregulation in TB, can be targeted for therapeutic interventions and treatment outcomes.

Performance evaluation of Truenat MTB and Truenat MTB-RIF DX assays in comparison to gene XPERT MTB/RIF ultra for the diagnosis of pulmonary tuberculosis in Uganda

BACKGROUND

The World Health Organization endorsed Truenat MTB rapid molecular assay in 2020 and recommended additional in-country evaluation studies before uptake. We evaluated the accuracy and operational feasibility of Truenat MTB assay (Truenat) in comparison with GeneXpert Ultra and culture.

METHODS

In a cross-sectional study of 250 presumptive TB patients, participants were requested to provide a sputum sample on the day of their visit to the clinic. The sputum sample was homogenized and a portion was tested using GeneXpert Ultra as per the routine standard procedure and the other portion was tested using Truenat assay at the clinic laboratory. The second sample portion was processed for Concentrated Fluorescent smear Microscopy (CFM), LJ, and MGIT cultures. Truenat sensitivity and specificity were compared to GeneXpert Ultra and culture. Test performance characteristics and operational feasibility assessment data through interview of the study laboratory staff were also collected and summarized as proportions and percentages.

RESULTS

Of the 250 participants recruited in the study, the sensitivity and specificity of Truenat was n/N (%, 95%CI); 66/82 (80.5, 70.2-88.4) and 156/159 (98.1, 94.5-99.6) when compared with Ultra, 50/64 (89.3, 66.0-87.4) and 166/180 (92.2, 87.2-95.6) when compared with LJ, 58/71 (81.7,70.7-89.8) and 131/138 (94.9, 89.8-97.9) when compared to MGIT culture and 59/73 (80.8, 69.9-89.1) and 159/169 (94.1,89.3-97.1) when compared to LJ and/or MGIT culture. The sensitivity of Truenat was lower, 14/23 (60.9, 40.6-82.8) among smear-negative compared to 45/50 (90.0, 78.1-96.6) among smear-positive participants but not different by HIV status. There were no special training needs especially among laboratory personnel with previous GeneXpert /molecular test experience, 19/242 (7.8%) error/invalid, and 12 (17,4%) uninterpretable/indeterminate results mainly for rifampicin resistance determination. However, there were 3 (3.5%) of GeneXpert Ultra indeterminate results.

CONCLUSION

Among presumptive TB patients in Uganda, the Truenat assay has high sensitivity and specificity. The Truenat assay has acceptable operational feasibility attributes when compared with the GeneXpert Assay.

Advances in the detection and diagnosis of tuberculosis using optical-based devices

Tuberculosis (TB), a bacterial infection caused by Mycobacterium tuberculosis, is highly contagious and can lead to severe health complications if left untreated. This review article discusses the importance of early detection and treatment and its global incidence and epidemiology, emphasizing its impact on vulnerable populations and its role as a major cause of death worldwide. Furthermore, it highlights the challenges faced with diagnosing TB. To overcome these challenges, point-of-care devices have emerged as promising tools for rapid and accurate TB detection. These include devices such as nucleic acid amplification tests (NAATs), lateral flow assays (LFAs), and microfluidic-based assays, which offer advantages such as rapid results, portability, and the ability to detect drug-resistant strains. Optical-based devices, such as photonic micro-ring sensors, silicon platform-based sensors, plasmonic-based platforms, microfluidics, and smartphone imaging, are some of the highlighted optical-based devices with the potential to detect TB. These devices can detect TB in sputum samples with high sensitivity and specificity. Optical-based diagnostic devices have the potential to offer the advantages of detecting low concentrations of target molecules and being adaptable to detect multiple targets simultaneously. Using these devices in a clinical setting makes them suitable for their application in improving access to diagnostic testing that enables earlier detection and treatment of TB. Furthermore, these devices would improve TB's global health issue, which requires comprehensive research, prevention, and treatment efforts.

Sensitive Blood-Based Detection of HIV-1 and Mycobacterium tuberculosis Peptides for Disease Diagnosis by Immuno-Affinity Liquid Chromatography-Tandem Mass Spectrometry: A Method Development and Proof-of-Concept Study

BACKGROUND

Novel approaches that allow early diagnosis and treatment monitoring of both human immunodeficiency virus-1 (HIV-1) and tuberculosis disease (TB) are essential to improve patient outcomes.

METHODS

We developed and validated an immuno-affinity liquid chromatography-tandem mass spectrometry (ILM) assay that simultaneously quantifies single peptides derived from HIV-1 p24 and Mycobacterium tuberculosis (Mtb) 10-kDa culture filtrate protein (CFP10) in trypsin-digested serum derived from cryopreserved serum archives of cohorts of adults and children with/without HIV and TB.

RESULTS

ILM p24 and CFP10 results demonstrated good intra-laboratory precision and accuracy, with recovery values of 96.7% to 104.6% and 88.2% to 111.0%, total within-laboratory precision (CV) values of 5.68% to 13.25% and 10.36% to 14.92%, and good linearity (r2 > 0.99) from 1.0 to 256.0 pmol/L and 0.016 to 16.000 pmol/L, respectively. In cohorts of adults (n = 34) and children (n = 17) with HIV and/or TB, ILM detected p24 and CFP10 demonstrated 85.7% to 88.9% and 88.9% to 100.0% diagnostic sensitivity for HIV-1 and TB, with 100% specificity for both, and detected HIV-1 infection earlier than 3 commercial p24 antigen/antibody immunoassays. Finally, p24 and CFP10 values measured in longitudinal serum samples from children with HIV-1 and TB distinguished individuals who responded to TB treatment from those who failed to respond or were untreated, and who developed TB immune reconstitution inflammatory syndrome.

CONCLUSIONS

Simultaneous ILM evaluation of p24 and CFP10 results may allow for early TB and HIV detection and provide valuable information on treatment response to facilitate integration of TB and HIV diagnosis and management.

Molecular analysis of rpoB gene mutation in MTB detected isolates in a tertiary care centre (AGMC) of North-East, India

BACKGROUND

Rifampicin (RIF), one of the first line drug in treatment of tuberculosis. It acts on rpoB gene which encodes RNA polymerase β subunit. In 95% of RIF resistant cases, mutations are present in rpoB gene. Most of them are within 81bp RIF-resistance determining region (RRDR).Xpert MTB/RIF assay has been tremendously revolutionalised the diagnosis of tuberculosis (TB).Also sequencially detect bacteria and resistance to rifampicin (rif).Approximately 96% of rif-resistant Mycobacterium tuberculosis (MTB) strains worldwide, showed mutations in a region at the 507-533rd amino acid residuals (81 bp) in the MTB rpoB gene. Here evaluation is made about frequent regions of amplification and mutation in various codons of 81bp of rpoB gene in rif sensitive and rif resistant cases.

METHODS

A total of 4116 samples were received at Mycobacteriology laboratory, AGMC and processed in CBNAAT.Data of MTB detected samples were collected & statistically analysed to detect frequency of amplification & no amplification in various regions of 81bp of rpoB genes.

RESULTS

Out of 4116 samples, MTB was detected in 1323 samples. Among them 1291 (97.58%) cases were Rif sensitive (RS) and 32 (2.41%) cases were rif resistance (RR).Most of the MTBC detected samples showed amplification in probe A then in probe C.78.12% rif resistant cases showed mutation in either of the probe, commonest is probe E. Study also showed low bacillary loads in most of the RR cases.

CONCLUSION

Study highlighted variations in amplification of different regions of 81bp of rpoB gene in MTBC detected cases. North-east India, like other part of world, also showed highest frequency of mutation in probe E in rif resistant cases.

Determining cost and placement decisions for moderate complexity NAATs for tuberculosis drug susceptibility testing

BACKGROUND

Access to drug resistant testing for tuberculosis (TB) remains a challenge in high burden countries. Recently, the World Health Organization approved the use of several moderate complexity automated nucleic acid amplification tests (MC-NAAT) that have performance profiles suitable for placement in a range of TB laboratory tiers to improve drug susceptibility tests (DST) coverage.

METHODS

We conducted cost analysis of two MC-NAATs with different testing throughput: Lower Throughput (LT, < 24 tests per run) and Higher Throughput (HT, upto 90+ tests per run) for placement in a hypothetical laboratory in a resource limited setting. We used per-test cost as the main indicator to assess 1) drivers of cost by resource types and 2) optimized levels of annual testing volumes for the respective MC-NAATs.

RESULTS

The base-case per test cost of $18.52 (range: $13.79 - $40.70) for LT test and $15.37 (range: $9.61 - $37.40) for HT test. Per test cost estimates were most sensitive to the number of testing days per week, followed by equipment costs and TB-specific workloads. In general, HT NAATs were cheaper at all testing volume levels, but at lower testing volumes (less than 2,000 per year) LT tests can be cheaper if the durability of the testing system is markedly better and/or procured equipment costs are lower than that of HT NAAT.

CONCLUSION

Assuming equivalent performance and infrastructural needs, placement strategies for MC-NAATs need to be prioritized by laboratory system's operational factors, testing demands, and costs.

A CRISPR-Cas12a-based platform for ultrasensitive rapid highly specific detection of Mycobacterium tuberculosis in clinical application

Tuberculosis, caused by Mycobacterium tuberculosis (MTB), is the second leading cause of death after COVID-19 pandemic. Here, we coupled multiple cross displacement amplification (MCDA) technique with CRISPR-Cas12a-based biosensing system to design a novel detection platform for tuberculosis diagnosis, termed MTB-MCDA-CRISPR. MTB-MCDA-CRISPR pre-amplified the specific sdaA gene of MTB by MCDA, and the MCDA results were then decoded by CRISPR-Cas12a-based detection, resulting in simple visual fluorescent signal readouts. A set of standard MCDA primers, an engineered CP1 primer, a quenched fluorescent ssDNA reporter, and a gRNA were designed targeting the sdaA gene of MTB. The optimal temperature for MCDA pre-amplification is 67°C. The whole experiment process can be completed within one hour, including sputum rapid genomic DNA extraction (15 minutes), MCDA reaction (40 minutes), and CRISPR-Cas12a-gRNA biosensing process (5 minutes). The limit of detection (LoD) of the MTB-MCDA-CRISPR assay is 40 fg per reaction. The MTB-MCDA-CRISPR assay does not cross reaction with non-tuberculosis mycobacterium (NTM) strains and other species, validating its specificity. The clinical performance of MTB-MCDA-CRISPR assay was higher than that of the sputum smear microscopy test and comparable to that of Xpert method. In summary, the MTB-MCDA-CRISPR assay is a promising and effective tool for tuberculosis infection diagnosis, surveillance and prevention, especially for point-of-care (POC) test and field deployment in source-limited regions.

Evaluation of the performances of InnowaveDx MTB-RIF assay in the diagnosis of pulmonary tuberculosis using bronchoalveolar lavage fluid

OBJECTIVE

To evaluate the tuberculosis diagnostic performance of the InnowaveDx MTB-RIF assay (InnowaveDx test) in bronchoalveolar lavage fluid (BALF).

METHODS

A total of 213 BALF samples from suspected PTB patients were analyzed. AFB smear, culture, Xpert, Innowavedx test, CapitalBio test and simultaneous amplification and testing (SAT) were performed.

RESULTS

Of the 213 patients included in the study, 163 were diagnosed with PTB, and 50 were TB negative. Using the final clinical diagnosis as the reference, the sensitivity of InnowaveDx assay was 70.6%, which was significantly higher than the values achieved using the other methods (P < 0.05), and the specificity was 88.0%, which was comparable with other methods (P > 0.05). Among the 83 PTB cases with negative culture results, the detection rate of InnowaveDx assay was significantly higher than those of AFB smear, Xpert, CapitalBio test and SAT (P < 0.05). Kappa analysis was used to compare the agreement of InnowaveDx and Xpert in detecting RIF sensitivity, and the result showed the Kappa value was 0.78.

CONCLUSIONS

The InnowaveDx test is a sensitive, rapid and cost-effective tool for PTB diagnosis. In addition, the sensitivity of InnowaveDx to RIF in samples with low TB load should be interpreted with caution in light of other clinical data.

Stool specimen for diagnosis of pulmonary tuberculosis in adults: a systematic review

OBJECTIVE

To assess the diagnostic accuracy of stool specimens to diagnose pulmonary tuberculosis (PTB) in adults.

DESIGN

Systematic review.

DATA SOURCES

MEDLINE (Ovid), Embase (Ovid), Web of Science and the Cochrane database were searched from inception to 9 March 2023-10 March 2023 using a comprehensive search strategy; reference lists of selected articles and relevant review articles were manually searched.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Studies in English reporting diagnostic performance of stool specimens against respiratory specimens using mycobacterial culture or smear microscopy or Xpert assay to diagnose PTB in adults were eligible for this systematic review.

DATA EXTRACTION AND SYNTHESIS

Two reviewers independently screened the retrieved citations and extracted data. The risk of bias and applicability of results were assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 tool. Narrative data synthesis was performed.

RESULTS

A total of 1658 citations were screened, and 28 full-text articles were assessed. Nine studies met the inclusion criteria. The reported sensitivity and specificity of stool culture varied between 21.4% and 63.9%, and 61.5% and 100%, respectively. In stool smear microscopy, sensitivities and specificities ranged from 12.1% to 53.9%, and from 79.5% to 100%, respectively. The reported sensitivities of PCR assays, including Xpert assays, ranged from 69.7% to 100%, with specificities ranging from 69.8% to 100%. Most of the studies had a low risk of bias and a low applicability concern in all domains.

CONCLUSION

This systematic review could not conclude on the diagnostic accuracy of stool specimens for PTB diagnosis in adults. Further studies are required to evaluate the accuracy of stool specimens in adults to enable meta-analyses in updates of this review as well as other systematic reviews.

PROSPERO REGISTRATION NUMBER

CRD42021245203.

Updating the WHO target product profile for next-generation Mycobacterium tuberculosis drug susceptibility testing at peripheral centres

There were approximately 10 million tuberculosis (TB) cases in 2020, of which 500,000 were drug-resistant. Only one third of drug-resistant TB cases were diagnosed and enrolled on appropriate treatment, an issue partly driven by a lack of rapid, accurate drug-susceptibility testing (DST) tools deployable in peripheral settings. In 2014, World Health Organization (WHO) published target product profiles (TPPs) which detailed minimal and optimal criteria to address high-priority TB diagnostic needs, including DST. Since then, the TB community's needs have evolved; new treatment regimens, changes in TB definitions, further emergence of drug resistance, technological advances, and changing end-users requirements have necessitated an update. The DST TPP's revision was therefore undertaken by WHO with the Stop TB Partnership New Diagnostics Working Group. We describe the process of updating the TPP for next-generation TB DST for use at peripheral centres, highlight key updates, and discuss guidance regarding technical and operational specifications.

An Analytic Feasibility Study of the BD MAX™ MDR-TB Assay for Testing of Non-Sputum Specimens for Detection of the Mycobacterium tuberculosis Complex (MTBC) and Isoniazid (INH) and Rifampin (RIF) Resistance

Rapid diagnosis of tuberculosis and drug resistance in extrapulmonary specimens can be challenging. The BD MAX™ multidrug resistant (MDR)-TB assay (BD MAX™) has demonstrated high sensitivity and specificity for the detection of the Mycobacterium tuberculosis complex (MTBC) as well as resistance to INH and Rifampin (RIF) in pulmonary specimens but has not been rigorously assessed in extrapulmonary samples. We evaluated the diagnostic accuracy of the BD MAX™ assay for the detection of MTBC and drug resistance in extrapulmonary specimens spiked with MTBC from the Johns Hopkins strain collection. A total of 1083 tests were performed across multiple sample types, with an overall percent agreement of 94.8% (795/839) for detection of MTBC and 99% (379/383) and 96.4% (323/335) for determination of INH and RIF resistance-conferring mutations, respectively. The BD MAX™ assay provides same day detection of MTBC and drug-resistance results and could be a beneficial diagnostic test in extrapulmonary sample types.

Meta-Analysis and Data Mining-Based Study on the Expression Characteristics of Inflammatory Factors and Causes of Recurrence in Spinal Tuberculosis

With the rapid development of modern medical information technology, hospitals are accumulating huge amounts of clinical data while providing medical services to patients, and in the era of big data, how to mine valuable information from the huge amount of clinical data so as to make new contributions to future disease diagnosis and medical research. In order to solve this problem, more and more scholars have introduced data mining techniques into the medical field in recent years, and mining and analysing medical data is a hot topic at present. If spinal TB is detected and treated early, not only can spinal deformities be prevented and treated but also the course of treatment can be shortened, the financial burden on the patient can be reduced, spinal function can be maintained, and eradication can be achieved without the need for surgical intervention. Early detection of spinal tuberculosis is the key to preventing and treating it. Therefore, in this paper, we use meta-analysis and data mining techniques to process and analyse the medical data of spinal tuberculosis disease, its main inflammatory factors expression characteristics, and the causes of patient recurrence.

Diagnostic Accuracy of the Truenat MTB Plus Assay and Comparison with the Xpert MTB/RIF Assay to Detect Tuberculosis among Hospital Outpatients in Cameroon

The Truenat MTB Plus assay is a rapid molecular test that has been recommended by the World Health Organization since 2020 as an initial test to detect tuberculosis (TB). The WHO highlighted the need to further evaluate assay performance to inform future recommendations, including in people living with HIV and compared to the Xpert MTB/RIF assay. We conducted a prospective evaluation of the diagnostic accuracy of the Truenat assay in Cameroon, a country with a high burden of HIV/TB. Adult outpatients were recruited at four hospitals; demographic information and medical history were collected, and participants produced two sputum specimens. Truenat and Xpert testing was performed on the same specimen, and performance was compared to TB culture as the reference standard. From November 2019 to December 2020, 945 participants were enrolled and included in the analysis. Among 251 participants with culture-positive TB, the sensitivity of Truenat MTB Plus was 91% (95% confidence interval [CI], 86 to 94%), similar to Xpert (90%; 95% CI, 86 to 93%). Among 74 HIV-positive participants with culture-positive TB, the sensitivity of Truenat MTB Plus was 85% (95% CI, 75 to 92%) compared to 81% for Xpert (95% CI, 70 to 89%). Among 47 participants with smear-negative TB, the sensitivity of Truenat MTB Plus was 55% (95% CI, 40 to 70%), similar to Xpert (53%; 95% CI, 38 to 68%). The specificity of Truenat MTB Plus was 96% (95% CI, 94 to 97%) compared to 99% (95% CI, 97 to 99%) for Xpert. For TB detection compared to the reference standard of TB culture, the performance of the Truenat MTB Plus assay was similar to that of Xpert in this population, including among people living with HIV.

Gaps and Interventions across the Diagnostic Care Cascade of TB Patients at the Level of Patient, Community and Health System: A Qualitative Review of the Literature

Tuberculosis (TB) continues to be one of the important public health concerns globally, and India is among the seven countries with the largest burden of TB. There has been a consistent increase in the notifications of TB cases across the globe. However, the 2018 estimates envisage a gap of about 30% between the incident and notified cases of TB, indicating a significant number of patients who remain undiagnosed or ‘missed’. It is important to understand who is ‘missed’, find this population, and provide quality care. Given these complexities, we reviewed the diagnostic gaps in the care cascade for TB. We searched Medline via PubMed and CENTRAL databases via the Cochrane Library. The search strategy for PubMed was tailored to individual databases and was as: ((((((tuberculosis[Title/Abstract]) OR (TB[Title/Abstract])) OR (koch *[Title/Abstract])) OR (“tuberculosis”[MeSH Terms]))) AND (((diagnos *) AND (“diagnosis”[MeSH Terms])))). Furthermore, we screened the references list of the potentially relevant studies to seek additional studies. Studies retrieved from these electronic searches and relevant references included in the bibliography of those studies were reviewed. Original studies in English that assessed the causes of diagnostic gaps and interventions used to address them were included. Delays in diagnosis were found to be attributable to both the individuals’ and the health system’s capacity to diagnose and promptly commence treatment. This review provides insights into the diagnostic gaps in a cascade of care for TB and different interventions adopted in studies to close this gap. The major diagnostic gaps identified in this review are as follows: people may not have access to TB diagnostic tests, individuals are at a higher risk of missed diagnosis, services are available but people may not seek care with a diagnostic facility, and patients are not diagnosed despite reaching health facilities. Therefore, reaching the goal to End TB requires putting in place models and methods to provide prompt and quality assured diagnosis to populations at par.

Fluorescence In Situ Hybridization (FISH) Tests for Identifying Protozoan and Bacterial Pathogens in Infectious Diseases

Diagnosing and treating many infectious diseases depends on correctly identifying the causative pathogen. Characterization of pathogen-specific nucleic acid sequences by PCR is the most sensitive and specific method available for this purpose, although it is restricted to laboratories that have the necessary infrastructure and finance. Microscopy, rapid immunochromatographic tests for antigens, and immunoassays for detecting pathogen-specific antibodies are alternative and useful diagnostic methods with different advantages and disadvantages. Detection of ribosomal RNA molecules in the cytoplasm of bacterial and protozoan pathogens by fluorescence in-situ hybridization (FISH) using sequence-specific fluorescently labelled DNA probes, is cheaper than PCR and requires minimal equipment and infrastructure. A LED light source attached to most laboratory light microscopes can be used in place of a fluorescence microscope with a UV lamp for FISH. A FISH test hybridization can be completed in 30 min at 37 °C and the whole test in less than two hours. FISH tests can therefore be rapidly performed in both well-equipped and poorly-resourced laboratories. Highly sensitive and specific FISH tests for identifying many bacterial and protozoan pathogens that cause disease in humans, livestock and pets are reviewed, with particular reference to parasites causing malaria and babesiosis, and mycobacteria responsible for tuberculosis.

Stool-based Xpert MTB/RIF assay for the diagnosis of pulmonary tuberculosis in children at a teaching and referral hospital in Southwest Ethiopia

BACKGROUND

Diagnosis of tuberculosis (TB) in children is challenging mainly due to the difficulty of obtaining respiratory specimen and lack of sensitive diagnostic tests. The objective of this study was to evaluate the diagnostic performance of Xpert MTB/RIF (Xpert here after) for the diagnosis of pulmonary TB (PTB) from stool specimen in children.

METHODS

A cross-sectional study was conducted among consecutively recruited children (less than 15 years old) with presumptive PTB at Jimma Medical Center, Ethiopia. One pulmonary specimen (expectorated sputum or gastric aspirate) was collected from each participant and tested for TB by Xpert and Lowenstein-Jensen (LJ) culture. In addition, one stool specimen per child was collected and tested by Xpert after a single step, centrifuge-free stool processing method adapted from KNCV TB Foundation. Diagnostic performance of Xpert was calculated with reference to LJ culture and to a composite reference standards (CRS) comprising of confirmed TB (positive by Xpert and/or culture) and unconfirmed TB (clinical diagnosis with improvement after anti-TB treatment).

RESULTS

A total of 178 children were enrolled; 152 of whom had complete microbiological results. Overall, TB was diagnosed in 13.2% (20/152) of the children with presumptive TB. Of these, only ten had microbiologically confirmed TB (positive Xpert and/or culture) and the remaining ten were clinically diagnosed with positive response to anti-TB treatment and were classified as unconfirmed TB. Stool Xpert had sensitivity of 100% (95%CI: 66.4-100) and specificity of 99.3% (95%CI: 96.2-100) compared to culture; however, the sensitivity was decreased to 50% (95%CI: 27.2-72.8) when compared to CRS. The Xpert on gastric aspirate had sensitivity of 77.8% (95%CI: 40-97.2) compared to culture and 40% (95%CI: 19.1-64) compared to CRS.

CONCLUSIONS

The sensitivity of Xpert for stool sample is comparable to that for gastric aspirate. Stool sample is a potential alternative to pulmonary specimen in the diagnosis of pulmonary TB in children using Xpert.

A new blood-based RNA signature (R9), for monitoring effectiveness of tuberculosis treatment in a South Indian longitudinal cohort

Tuberculosis (TB) treatment involves a multidrug regimen for six months, and until two months, it is unclear if treatment is effective. This delay can lead to the evolution of drug resistance, lung damage, disease spread, and transmission. We identify a blood-based 9-gene signature using a computational pipeline that constructs and interrogates a genome-wide transcriptome-integrated protein-interaction network. The identified signature is able to determine treatment response at week 1-2 in three independent public datasets. Signature-based R9-score correctly detected treatment response at individual timepoints (204 samples) from a newly developed South Indian longitudinal cohort involving 32 patients with pulmonary TB. These results are consistent with conventional clinical metrics and can discriminate good from poor treatment responders at week 2 (AUC 0.93(0.81-1.00)). In this work, we provide proof of concept that the R9-score can determine treatment effectiveness, making a case for designing a larger clinical study.

Diagnostic performance of oral swabs for non-sputum based TB diagnosis in a TB/HIV endemic setting

OBJECTIVE

We evaluated diagnostic performance of oral swab analysis (OSA) for tuberculosis (TB) in a high HIV/TB burden setting in Kenya.

METHODS

In this cross-sectional study, buccal swabs and sputum were collected from 100 participants with suspected TB in outpatient clinics in Kenya at enrollment and subsequent morning visits. Buccal swabs underwent IS6110-targeted qPCR analysis. Sputum was evaluated by Xpert MTB/RIF (Xpert) and culture. Diagnostic performance of OSA for TB diagnosis was evaluated relative to a combined reference of sputum Xpert and culture.

RESULTS

Among 100 participants, 54% were living with HIV (PLHIV). Twenty percent (20/100) of participants had confirmed TB (19/20 [95%] culture-positive, 17/20 [85%] Xpert-positive). Overall buccal swab sensitivity was 65.0% (95% CI 40.8-84.6%) vs. sputum Xpert/culture and 76.5% (95% CI 50.1-93.2%) vs. sputum Xpert alone. Specificity was 81.3% (95% CI 71.0-89.1%) and 81.9% (95% CI 72.0-89.5%) compared to sputum Xpert/culture and Xpert alone, respectively. Sensitivity among PLHIV (n = 54) with suspected TB was 83.3% (95% CI 35.9-99.6%) vs. sputum Xpert/culture and 100% (95% CI 47.8-100.0%) vs. sputum Xpert alone. Among participants with TB, mean OSA threshold quantitation cycle (Cq) value was lower (stronger signal) at subsequent morning compared to enrolment visit (33.4 SD ± 3.7 vs. 35.2 SD ± 2.9, p = 0.009).

CONCLUSIONS

In this pilot study, results confirm M. tuberculosis DNA is detectable in oral swabs including among PLHIV with fair diagnostic performance. Further work is needed to optimize OSA and evaluate its utility in diverse settings.

Metabolomics Strategy Assisted by Transcriptomics Analysis to Identify Potential Biomarkers Associated with Tuberculosis

Purpose

To investigate the dysregulated pathways and identify reliable diagnostic biomarkers for tuberculosis using integrated analysis of metabolomics and transcriptomics.

Methods

Three groups of samples, untargeted metabolomics analysis of healthy controls (HC), latent tuberculosis infection patients (LTBI), and active tuberculosis patients (TB), were analyzed using gas chromatography time-of-flight mass spectrometry (GC-TOF MS) and ultra-high performance liquid chromatography-quantitative mass spectrometry (UHPLC-QE-MS). Both univariate and multivariate and statistical analyses were used to select differential metabolites (DMs) among group comparison, and LASSO regression analysis was employed to discover potential diagnostic biomarkers. Metabolite set enrichment analysis was performed to identify the altered metabolic pathways specifically in patients with TB. Meanwhile, a transcriptomic dataset GSEG4992 was downloaded from the GEO database to explore the differentially expressed genes (DEGs) between TB and HC identified in significantly enriched pathways. Finally, an integrative analysis of DMs and DEGs was performed to investigate the possible molecular mechanisms of TB.

Results

Thirty-three specific metabolites were significantly different between TB and HC, of which 7 (5-hydroxyindoleacetic acid, isoleucyl-isoleucine, heptadecanoic acid, indole acetaldehyde, 5-ethyl-2,4-dimethyloxazole, and 2-hydroxycaproic acid, unknown 71) were chosen as combinational potential biomarkers for TB. The area under the curve (AUC) value of these biomarkers was 0.97 (95% CI: 0.92–1.00). Metabolites set enrichment analysis (MSEA) displayed that there were 3 significantly enriched pathways among all. The genes in 3 significantly enriched pathways were further analyzed, of which 9(ALDH3B1, BCAT1, BCAT2, GLYAT, GOT1, IL4I1, MIF, SDS, SDSL) were expressed differentially. The area under the curve (AUC) values of these DEGs enriched in pathways mostly were greater than 0.8. As a result, a connected network of metabolites and genes in the pathways were established, which provides insights into the credibility of selected metabolites.

Conclusion

The newly identified metabolic biomarkers display a high potential to be developed into a promising tool for TB screening, diagnosis, and therapeutic effect monitoring.

Detection and quantification of Mycobacterium tuberculosis antigen CFP10 in serum and urine for the rapid diagnosis of active tuberculosis disease

Outside of the ongoing COVID-19 pandemic, tuberculosis is the leading cause of infectious disease mortality globally. Currently, there is no commercially available point-of-care diagnostic that is rapid, inexpensive, and highly sensitive for the diagnosis of active tuberculosis disease. Here we describe the development and optimization of a novel, highly sensitive prototype bioelectronic tuberculosis antigen (BETA) assay to detect tuberculosis-specific antigen, CFP10, in small-volume serum and urine samples. In this proof-of-concept study we evaluated the performance of the BETA assay using clinical specimens collected from presumptive tuberculosis patients from three independent cohorts. Circulating CFP10 antigen was detected in ALL serum (n = 19) and urine (n = 3) samples from bacteriologically confirmed tuberculosis patients who were untreated or had less than one week of treatment at time of serum collection, successfully identifying all culture positive tuberculosis patients. No CFP10 antigen was detected in serum (n = 7) or urine (n = 6) samples from individuals who were determined to be negative for tuberculosis disease. Additionally, antigen quantification using the BETA assay of paired serum samples collected from tuberculosis patients (n = 8) both before and after treatment initiation, indicate consistently declining within-person levels of CFP10 antigen during treatment. This novel, low-cost assay demonstrates potential as a rapid, non-sputum-based, point-of-care tool for the diagnosis of tuberculosis disease.

Past and Present Approaches to Diagnosis of Active Pulmonary Tuberculosis

Tuberculosis disease continues to contribute to the mortality burden globally. Due to the several shortcomings of the available diagnostic methods, tuberculosis disease continues to spread. The difficulty to obtain sputum among the very ill patients and the children also affects the quick diagnosis of tuberculosis disease. These challenges warrant investigating different sample types that can provide results in a short time. Highlighted in this review are the approved pulmonary tuberculosis diagnostic methods and ongoing research to improve its diagnosis. We used the PRISMA guidelines for systematic reviews to search for studies that met the selection criteria for this review. In this review we found out that enormous biosignature research is ongoing to identify host biomarkers that can be used as predictors of active PTB disease. On top of this, more research was also being done to improve already existing diagnostic tests. Host markers required more optimization for use in different settings given their varying sensitivity and specificity in PTB endemic and non-endemic settings.

Performance assessment of SD Bioline TB MPT64 assay for the diagnosis of Mycobacterium tuberculosis complex in Lagos, Nigeria

This study assessed the performance of SD Bioline MPT64 immunochromatographic test for the identification of Mycobacterium tuberculosis complex (MTBC) in Nigeria.A total of 157 mycobacterial isolates, comprising 120 (76.4%) MTBC (M. tuberculosis, 112; M. africanum, 5; M. bovis, 3) and 37 (23.6%) non-tuberculous mycobacteria (NTM) isolates from patients attending six DOTS centers in Lagos between June 2012 and July 2014 were analyzed. All the isolates were grown on Bactec MGIT960 liquid media and identified in parallel by the conventional method and MPT64 immunochromatographic test. Discrepant results were resolved using the line probe assay.The comorbid disease rates for HIV and type 2 diabetes were 20.9% and 8.2%, respectively. Compared to the conventional method, SD Bioline MPT64 identified 117 MTBC isolates correctly, producing a sensitivity of 97.5% (95% CI, 92.9-99.2) at a shorter growing median time of 11 days compared to 26 days by the conventional method. The three undetected MTBC were confirmed by the line probe assay to be M. tuberculosis strains. The test also identified all the NTM correctly producing a specificity of 100% (95% CI, 90.7-100).This study supports the integration of SD Bioline TB MPT64 antigen test into diagnostic workflow for rapid MTBC case identification in Nigeria.

The Evaluation and Validation of Blood-Derived Novel Biomarkers for Precise and Rapid Diagnosis of Tuberculosis in Areas With High-TB Burden

Tuberculosis (TB) remains a highly contagious public health threat. Precise and prompt diagnosis and monitoring of treatment responses are urgently needed for clinics. To pursue novel and satisfied host blood-derived biomarkers, we streamlined a bioinformatic pipeline by integrating differentially expressed genes, a gene co-expression network, and short time-series analysis to mine the published transcriptomes derived from whole blood of TB patients in the GEO database, followed by validating the diagnostic performance of biomarkers in both independent datasets and blood samples of Chinese patients using quantitative real-time PCR (qRT-PCR). We found that four genes, namely UBE2L6 (Ubiquitin/ISG15-conjugating enzyme E2 L6), BATF2 (Basic leucine zipper transcriptional factor ATF-like), SERPING1 (Plasma protease C1 inhibitor), and VAMP5 (Vesicle-associated membrane protein 5), had high diagnostic value for active TB. The transcription levels of these four gene combinations can reach up to 88% sensitivity and 78% specificity (average) for the diagnosis of active TB; the highest sensitivity can achieve 100% by parallel of BATF2 and VAMP5, and the highest specificity can reach 89.5% through a combination of SERPIG1, UBE2L6, and VAMP5, which were significantly higher than 75.3% sensitivity and 69.1% specificity by T-SPOT.TB in the same patients. Quite unexpectedly, the gene set can assess the efficacy of anti-TB response and differentiate active TB from Latent TB infection. The data demonstrated these four biomarkers might have great potency and advantage over IGRAs in the diagnosis of TB.

Multicenter Study of the Accuracy of the BD MAX Multidrug-resistant Tuberculosis Assay for Detection of Mycobacterium tuberculosis Complex and Mutations Associated With Resistance to Rifampin and Isoniazid

BACKGROUND

Tuberculosis (TB) control is hindered by absence of rapid tests to identify Mycobacterium tuberculosis (MTB) and detect isoniazid (INH) and rifampin (RIF) resistance. We evaluated the accuracy of the BD MAX multidrug-resistant (MDR)-TB assay (BD MAX) in South Africa, Uganda, India, and Peru.

METHODS

Outpatient adults with signs/symptoms of pulmonary TB were prospectively enrolled. Sputum smear microscopy and BD MAX were performed on a single raw sputum, which was then processed for culture and phenotypic drug susceptibility testing (DST), BD MAX, and Xpert MTB/RIF (Xpert).

RESULTS

1053 participants with presumptive TB were enrolled (47% female; 32% with human immunodeficiency virus). In patients with confirmed TB, BD MAX sensitivity was 93% (262/282 [95% CI, 89-95%]); specificity was 97% (593/610 [96-98%]) among participants with negative cultures on raw sputa. BD MAX sensitivity was 100% (175/175 [98-100%]) for smear-positive samples (fluorescence microscopy), and 81% (87/107 [73-88%]) in smear-negative samples. Among participants with both BD MAX and Xpert, sensitivity was 91% (249/274 [87-94%]) for BD MAX and 90% (246/274 [86-93%]) for Xpert on processed sputa. Sensitivity and specificity for RIF resistance compared with phenotypic DST were 90% (9/10 [60-98%]) and 95% (211/222 [91-97%]), respectively. Sensitivity and specificity for detection of INH resistance were 82% (22/27 [63-92%]) and 100% (205/205 [98-100%]), respectively.

CONCLUSIONS

The BD MAX MDR-TB assay had high sensitivity and specificity for detection of MTB and RIF and INH drug resistance and may be an important tool for rapid detection of TB and MDR-TB globally.

Validation of Differentially Expressed Immune Biomarkers in Latent and Active Tuberculosis by Real-Time PCR

Tuberculosis (TB) remains a major global threat and diagnosis of active TB ((ATB) both extra-pulmonary (EPTB), pulmonary (PTB)) and latent TB (LTBI) infection remains challenging, particularly in high-burden countries which still rely heavily on conventional methods. Although molecular diagnostic methods are available, e.g., Cepheid GeneXpert, they are not universally available in all high TB burden countries. There is intense focus on immune biomarkers for use in TB diagnosis, which could provide alternative low-cost, rapid diagnostic solutions. In our previous gene expression studies, we identified peripheral blood leukocyte (PBL) mRNA biomarkers in a non-human primate TB aerosol-challenge model. Here, we describe a study to further validate select mRNA biomarkers from this prior study in new cohorts of patients and controls, as a prerequisite for further development. Whole blood mRNA was purified from ATB patients recruited in the UK and India, LTBI and two groups of controls from the UK (i) a low TB incidence region (CNTRLA) and (ii) individuals variably-domiciled in the UK and Asia ((CNTRLB), the latter TB high incidence regions). Seventy-two mRNA biomarker gene targets were analyzed by qPCR using the Roche Lightcycler 480 qPCR platform and data analyzed using GeneSpring™ 14.9 bioinformatics software. Differential expression of fifty-three biomarkers was confirmed between MTB infected, LTBI groups and controls, seventeen of which were significant using analysis of variance (ANOVA): CALCOCO2, CD52, GBP1, GBP2, GBP5, HLA-B, IFIT3, IFITM3, IRF1, LOC400759 (GBP1P1), NCF1C, PF4V1, SAMD9L, S100A11, TAF10, TAPBP, and TRIM25. These were analyzed using receiver operating characteristic (ROC) curve analysis. Single biomarkers and biomarker combinations were further assessed using simple arithmetic algorithms. Minimal combination biomarker panels were delineated for primary diagnosis of ATB (both PTB and EPTB), LTBI and identifying LTBI individuals at high risk of progression which showed good performance characteristics. These were assessed for suitability for progression against the standards for new TB diagnostic tests delineated in the published World Health Organization (WHO) technology product profiles (TPPs).

Transcriptomic signatures for diagnosing tuberculosis in clinical practice: a prospective, multicentre cohort study

Background

Blood transcriptomic signatures for diagnosis of tuberculosis have shown promise in case-control studies, but none have been prospectively designed or validated in adults presenting with the full clinical spectrum of suspected tuberculosis, including extrapulmonary tuberculosis and common differential diagnoses that clinically resemble tuberculosis. We aimed to evaluate the diagnostic accuracy of transcriptomic signatures in patients presenting with clinically suspected tuberculosis in routine practice.

Methods

The Validation of New Technologies for Diagnostic Evaluation of Tuberculosis (VANTDET) study was nested within a prospective, multicentre cohort study in secondary care in England (IDEA 11/H0722/8). Patients (aged ≥16 years) suspected of having tuberculosis in the routine clinical inpatient and outpatient setting were recruited at ten National Health Service hospitals in England for IDEA and were included in VANTDET if they provided consent for genomic analysis. Patients had whole blood taken for microarray analysis to measure abundance of transcripts and were followed up for 6–12 months to determine final diagnoses on the basis of predefined diagnostic criteria. The diagnostic accuracy of six signatures derived from the cohort and three previously published transcriptomic signatures with potentially high diagnostic performance were assessed by calculating area under the receiver-operating characteristic curves (AUC-ROCs), sensitivities, and specificities.

Findings

Between Nov 25, 2011, and Dec 31, 2013, 1162 participants were enrolled. 628 participants (aged ≥16 years) were included in the analysis, of whom 212 (34%) had culture-confirmed tuberculosis, 89 (14%) had highly probable tuberculosis, and 327 (52%) had tuberculosis excluded. The novel signature with highest performance for identifying all active tuberculosis gave an AUC-ROC of 0·87 (95% CI 0·81–0·92), sensitivity of 77% (66–87), and specificity of 84% (74–91). The best-performing published signature gave an AUC-ROC of 0·83 (0·80–0·86), sensitivity of 78% (73–83), and specificity of 76% (70–80). For detecting highly probable tuberculosis, the best novel signature yielded results of 0·86 (0·71–0·95), 77% (56–94%), and 77% (57–95%). None of the relevant cohort-derived or previously published signatures achieved the WHO-defined targets of paired sensitivity and specificity for a non-sputum-based diagnostic test.

Interpretation

In a clinically representative cohort in routine practice in a low-incidence setting, transcriptomic signatures did not have adequate accuracy for diagnosis of tuberculosis, including in patients with highly probable tuberculosis where the unmet need is greatest. These findings suggest that transcriptomic signatures have little clinical utility for diagnostic assessment of suspected tuberculosis.

Funding

National Institute for Health Research.

The potential impact of urine-LAM diagnostics on tuberculosis incidence and mortality: A modelling analysis

BACKGROUND

Lateral flow urine lipoarabinomannan (LAM) tests could offer important new opportunities for the early detection of tuberculosis (TB). The currently licensed LAM test, Alere Determine TB LAM Ag ('LF-LAM'), performs best in the sickest people living with HIV (PLHIV). However, the technology continues to improve, with newer LAM tests, such as Fujifilm SILVAMP TB LAM ('SILVAMP-LAM') showing improved sensitivity, including amongst HIV-negative patients. It is important to anticipate the epidemiological impact that current and future LAM tests may have on TB incidence and mortality.

METHODS AND FINDINGS

Concentrating on South Africa, we examined the impact that widening LAM test eligibility would have on TB incidence and mortality. We developed a mathematical model of TB transmission to project the impact of LAM tests, distinguishing 'current' tests (with sensitivity consistent with LF-LAM), from hypothetical 'future' tests (having sensitivity consistent with SILVAMP-LAM). We modelled the impact of both tests, assuming full adoption of the 2019 WHO guidelines for the use of these tests amongst those receiving HIV care. We also simulated the hypothetical deployment of future LAM tests for all people presenting to care with TB symptoms, not restricted to PLHIV. Our model projects that 2,700,000 (95% credible interval [CrI] 2,000,000-3,600,000) and 420,000 (95% CrI 350,000-520,000) cumulative TB incident cases and deaths, respectively, would occur between 2020 and 2035 if the status quo is maintained. Relative to this comparator, current and future LAM tests would respectively avert 54 (95% CrI 33-86) and 90 (95% CrI 55-145) TB deaths amongst inpatients between 2020 and 2035, i.e., reductions of 5% (95% CrI 4%-6%) and 9% (95% CrI 7%-11%) in inpatient TB mortality. This impact in absolute deaths averted doubles if testing is expanded to include outpatients, yet remains <1% of country-level TB deaths. Similar patterns apply to incidence results. However, deploying a future LAM test for all people presenting to care with TB symptoms would avert 470,000 (95% CrI 220,000-870,000) incident TB cases (18% reduction, 95% CrI 9%-29%) and 120,000 (95% CrI 69,000-210,000) deaths (30% reduction, 95% CrI 18%-44%) between 2020 and 2035. Notably, this increase in impact arises largely from diagnosis of TB amongst those with HIV who are not yet in HIV care, and who would thus be ineligible for a LAM test under current guidelines. Qualitatively similar results apply under an alternative comparator assuming expanded use of GeneXpert MTB/RIF ('Xpert') for TB diagnosis. Sensitivity analysis demonstrates qualitatively similar results in a setting like Kenya, which also has a generalised HIV epidemic, but a lower burden of HIV/TB coinfection. Amongst limitations of this analysis, we do not address the cost or cost-effectiveness of future tests. Our model neglects drug resistance and focuses on the country-level epidemic, thus ignoring subnational variations in HIV and TB burden.

CONCLUSIONS

These results suggest that LAM tests could have an important effect in averting TB deaths amongst PLHIV with advanced disease. However, achieving population-level impact on the TB epidemic, even in high-HIV-burden settings, will require future LAM tests to have sufficient performance to be deployed more broadly than in HIV care.

Profile of Nontuberculous Mycobacteria in Patients Suspected of Tuberculosis and Drug-Resistant Tuberculosis

Objective  Infections due to nontuberculous mycobacteria (NTM) is increasing globally and may present as drug-resistant tuberculosis (DRTB). In India, data on NTM prevalence and species diversity is limited. Present study was conducted to detect the prevalence and profile of NTM among patients suspected of DRTB using paraffin slide culture (PSC)and mycobacteria growth indicator tube (MGIT) culture methods for isolation of NTM. Material and Method  A total of 2,938 samples suspected of TB/DRTB were cultured on PSC and MGIT960. Species identification of mycobacterial isolate was done by sequencing of 16s ribosomal RNA gene. Result  Among 2938 samples, 35 (1.19%) were found positive for NTM by PSC and 9 (0.30%) were found positive by MGIT. The diversity of NTM species was high (13 species). Out of 35 NTM isolates by PSC, maximum 34.29% (12) isolates were found to be Mycobacterium fortuitum , followed by 11.43% (4) Mycobacterium abscessus and Mycobacterium chelonae , and 42.85% (15) were other species viz. 8.57% (3) were Mycobacterium intracellulare and Mycobacterium kansasii , 5.71% (2) were Mycobacterium peregrinum , and 2.85% (1) were Mycobacterium flavescens, Mycobacterium farcinogenes, Mycobacterium moriokanese, Mycobacterium wolinskyi, Mycobacterium simiae, Mycobacterium goodii , and Mycobacterium terrae each. Coinfection of Mycobacterium tuberculosis (MTB) and NTM was found in 60% (21) samples. Conclusion  Prevalence of NTM was low among multidrug resistant tuberculosis/TB suspected patients, similar to other studies done in India. PSC was found better than MGIT for the isolation of NTM, though poor separation of NTM and MTB on subculture may have led to false negativity in cases of coinfection. About 13 species were isolated; M. fortuitum was the most common of all. Since coinfection of NTM and TB can also occur, samples of patients suspected of NTM should be cultured on PSC even if positive for MTB.

Evaluation of the performance of an in-house duplex PCR assay targeting the IS6110 and rpoB genes for tuberculosis diagnosis in Cameroon

Background

Tuberculosis (TB) remains a major public health concern in many low-income countries accounting for approximately two-thirds of deaths in people living with human immunodeficiency virus (HIV) infection. With prompt, accurate and appropriate treatment, almost all TB disease can be cured. The present study was to evaluate the diagnostic performance of an in-house duplex PCR (D-PCR) using IS1610 and rpoB specific primers in sputum samples from TB suspected patients.

Methods

A hospital-based cross-sectional study was conducted at the Limbe and Buea Regional Hospitals of the South West Region of Cameroon from June 2016 to April 2017. Sputum samples, decontaminated with hypertonic saline/sodium hydroxide solution were centrifuged and pellets processed for smear microscopy, culture and DNA extraction. Suspected inhibition was resolved by serial dilution of genomic DNA. Results were compared to culture as gold standard as well as a Composite Reference Standard (CRS).

Results

A total of 129 participants aged between 5 to 82 years were enrolled in to the study. The median age of the participants was 37 years (interquartile range, IQR: 27–50 years), with 54.3% being male. Forty-seven samples (36.4%) were positive by direct sputum microscopy, 49 (38%) by microscopy after concentration, 51 (39.5%) by culture and 62 (40.1%) by D-PCR. PCR inhibition was resolved in 85.7% (18/21) of the samples that had inhibition. The overall sensitivity, specificity, positive and negative predictive values, positive and negative likelihood ratios and area under the curve AUC) of the D-PCR was 93.5, 94, 94, 94%, 15.6, 0.005 and 89.0% respectively using CRS as reference. The sensitivities of D-PCR observed among different sample categories were 95.7, 87.5 and 87.5% for smear-and culture-positives, smear-negative/culture-positive, and clinically diagnosed cases respectively.

Conclusion

IS1610 and rpoB duplex PCR using relatively cheap decontamination and DNA extraction methods in addition to simple serial dilutions to resolve PCR inhibition shows high sensitivity in the diagnosis of paucibacillary tuberculosis.

Laboratory Evaluation of a Lateral-Flow Cell for Molecular Detection of First-Line and Second-Line Antituberculosis Drug Resistance

Despite the WHO's call for universal drug susceptibility testing for all patients being evaluated for tuberculosis (TB), a lack of rapid diagnostic tests which can fully describe TB resistance patterns is a major challenge in ensuring that all persons diagnosed with drug-resistant TB are started on an appropriate treatment regime. We evaluated the accuracy of the Akonni Biosystems XDR-TB TruArray and lateral-flow cell (XDR-LFC), a novel multiplex assay to simultaneously detect mutations across seven genes that confer resistance to both first- and second-line anti-TB drugs. The XDR-LFC includes 271 discrete three-dimensional gel elements with target-specific probes for identifying mutations in katG, inhA promoter, and ahpC promoter (isoniazid), rpoB (rifampin), gyrA (fluoroquinolones), rrs and eis promoter (kanamycin), and rrs (capreomycin and amikacin). We evaluated XDR-LFC performance with 87 phenotypically and genotypically characterized clinical Mycobacterium tuberculosis isolates. The overall assay levels of accuracy for mutation detection in specific genes were 98.6% for eis promoter and 100.0% for the genes katG, inhA promoter, ahpC promoter, rpoB, gyrA, and rrs The sensitivity and specificity against phenotypic reference were 100% and 100% for isoniazid, 98.4% and 50% for rifampin (specificity increased to 100% once the strains with documented low-level resistance mutations in rpoB were excluded), 96.2% and 100% for fluoroquinolones, 92.6% and 100% for kanamycin, 93.9% and 97.4% for capreomycin, and 80% and 100% for amikacin. The XDR-LFC solution appears to be a promising new tool for accurate detection of resistance to both first- and second-line anti-TB drugs.

Urinary biomarkers of mycobacterial load and treatment response in pulmonary tuberculosis

BACKGROUNDControl of the tuberculosis (TB) pandemic remains hindered in part by a lack of simple and accurate measures of treatment efficacy, as current gold standard markers rely on sputum-based assays that are slow and challenging to implement. However, previous work identified urinary N1, N12-diacetylspermine (DiAcSpm), neopterin, hydroxykynurenine, N-acetylhexosamine, ureidopropionic acid, sialic acid, and mass-to-charge ratio (m/z) 241.0903 as potential biomarkers of active pulmonary TB (ATB). Here, we evaluated their ability to serve as biomarkers of TB treatment response and mycobacterial load.METHODSWe analyzed urine samples prospectively collected from 2 cohorts with ATB. A total of 34 study participants from African countries treated with first-line TB therapy rifampin, isoniazid, pyrazinamide, and ethambutol (HRZE) were followed for 1 year, and 35 participants from Haiti treated with either HRZE or an experimental drug were followed for 14 days. Blinded samples were analyzed by untargeted HPLC-coupled high-resolution TOF-mass spectrometry.RESULTSUrinary levels of all 7 molecules significantly decreased by week 26 of successful treatment (P = 0.01 to P < 0.0001) and positively correlated with sputum mycobacterial load (P < 0.0001). Urinary DiAcSpm levels decreased significantly in participants treated with HRZE as early as 14 days (P < 0.0001) but remained unchanged in cases of ineffective therapy (P = 0.14).CONCLUSIONUrinary DiAcSpm, neopterin, hydroxykynurenine, N-acetylhexosamine, ureidopropionic acid, sialic acid, and m/z 241.0903 reductions correlated with successful anti-TB treatment and sputum mycobacterial load. Urinary DiAcSpm levels exhibited reductions capable of differentiating treatment success from failure as early as 2 weeks after the initiation of chemotherapy, advocating its further development as a potentially simple, noninvasive biomarker for assessing treatment response and bacterial load.FUNDINGThis work was supported by the Clinical and Translational Science Center at Weill Cornell College of Medicine (NIH/NCATS 1 UL1 TR002384-02 and KL2TR000458), the Department of Defense (PR170782), the National Institute of Allergy and Infectious Disease grants (NIAID T32AI007613-16, K24 AI098627, and K23 AI131913), the NIH Fogarty International Center grants (R24 TW007988 and TW010062), NIH grant (R01 GM135926), the Abby and Howard P. Milstein Program in Chemical Biology and Translational Medicine, and the Tuberculosis Research Units Networks (TBRU-N, AI111143).

Detection of mutations in the rpoB gene of rifampicin-resistant Mycobacterium tuberculosis strains inhibiting wild type probe hybridization in the MTBDR plus assay by DNA sequencing directly from clinical specimens

Background

The potential of genetic testing for rapid and accurate diagnosis of drug-resistant Mycobacterium tuberculosis strains is vital for efficient treatment and reduction in dissemination. MTBDR plus assays rapidly detect mutations related to drug resistance and wild type sequences allied with susceptibility. Although these methods are promising, the examination of molecular level performance is essential for improved assay result interpretation and continued diagnostic development. Therefore this study aimed to determine novel mutations that were inhibiting wild type probe hybridization in the Line probe assay by DNA sequencing. Using data collected from Line Probe assay (GenoType MTBDRplus assay) the contribution of absent wild type probe hybridization to the detection of rifampicin resistance was assessed via comparison to a reference standard method i.e. DNA sequencing.

Results

Sequence analysis of the rpoB gene of 47 MTB resistant strains from clinical specimens showed that 37 had a single mutation, 9 had double mutations and one had triple mutations in the ropB gene.

Conclusions

The absence of wild type probe hybridization without mutation probe hybridization was mainly the result of the failure of mutation probe hybridization and the result of the novel or rare mutations. Additional probes are necessary to be included in the Line probe assay to improve the detection of rifampicin-resistant Mycobacterium tuberculosis strains.

A rapid triage test for active pulmonary tuberculosis in adult patients with persistent cough

Improved tuberculosis (TB) prevention and control depend critically on the development of a simple, readily accessible rapid triage test to stratify TB risk. We hypothesized that a blood protein-based host response signature for active TB (ATB) could distinguish it from other TB-like disease (OTD) in adult patients with persistent cough, thereby providing a foundation for a point-of-care (POC) triage test for ATB. Three adult cohorts consisting of ATB suspects were recruited. A bead-based immunoassay and machine learning algorithms identified a panel of four host blood proteins, interleukin-6 (IL-6), IL-8, IL-18, and vascular endothelial growth factor (VEGF), that distinguished ATB from OTD. An ultrasensitive POC-amenable single-molecule array (Simoa) panel was configured, and the ATB diagnostic algorithm underwent blind validation in an independent, multinational cohort in which ATB was distinguished from OTD with receiver operator characteristic-area under the curve (ROC-AUC) of 0.80 [95% confidence interval (CI), 0.75 to 0.85], 80% sensitivity (95% CI, 73 to 85%), and 65% specificity (95% CI, 57 to 71%). When host antibodies against TB antigen Ag85B were added to the panel, performance improved to 86% sensitivity and 69% specificity. A blood-based host response panel consisting of four proteins and antibodies to one TB antigen can help to differentiate ATB from other causes of persistent cough in patients with and without HIV infection from Africa, Asia, and South America. Performance characteristics approach World Health Organization (WHO) target product profile accuracy requirements and may provide the foundation for an urgently needed blood-based POC TB triage test.

The War against Tuberculosis: A Review of Natural Compounds and Their Derivatives

Tuberculosis (TB), caused by the bacterial organism Mycobacterium tuberculosis, pose a major threat to public health, especially in middle and low-income countries. Worldwide in 2018, approximately 10 million new cases of TB were reported to the World Health Organization (WHO). There are a limited number of medications available to treat TB; additionally, multi-drug resistant TB and extensively-drug resistant TB strains are becoming more prevalent. As a result of various factors, such as increased costs of developing new medications and adverse side effects from current medications, researchers continue to evaluate natural compounds for additional treatment options. These substances have the potential to target bacterial cell structures and may contribute to successful treatment. For example, a study reported that green and black tea, which contains epigallocatechin gallate (a phenolic antioxidant), may decrease the risk of contracting TB in experimental subjects; cumin (a seed from the parsley plant) has been demonstrated to improve the bioavailability of rifampicin, an important anti-TB medication, and propolis (a natural substance produced by honeybees) has been shown to improve the binding affinity of anti-TB medications to bacterial cell structures. In this article, we review the opportunistic pathogen M. tuberculosis, various potential therapeutic targets, available therapies, and natural compounds that may have anti-TB properties. In conclusion, different natural compounds alone as well as in combination with already approved medication regimens should continue to be investigated as treatment options for TB.

Closing gaps in the tuberculosis care cascade: an action-oriented research agenda

The care cascade-which evaluates outcomes across stages of patient engagement in a health system-is an important framework for assessing quality of tuberculosis (TB) care. In recent years, there has been progress in measuring care cascades in high TB burden countries; however, there are still shortcomings in our knowledge of how to reduce poor patient outcomes. In this paper, we outline a research agenda for understanding why patients fall through the cracks in the care cascade. The pathway for evidence generation will require new systematic reviews, observational cohort studies, intervention development and testing, and continuous quality improvement initiatives embedded within national TB programs. Certain gaps, such as pretreatment loss to follow-up and post-treatment disease recurrence, should be a priority given a relative paucity of high-quality research to understand and address poor outcomes. Research on interventions to reduce death and loss to follow-up during treatment should move beyond a focus on monitoring (or observation) strategies, to address patient needs including psychosocial and nutritional support. While key research questions vary for each gap, some patient populations may experience disparities across multiple stages of care and should be a priority for research, including men, individuals with a prior treatment history, and individuals with drug-resistant TB. Closing gaps in the care cascade will require investments in a bold and innovative action-oriented research agenda.

Unilateral or Bilateral Percutaneous Endoscopic Debridement and Lavage Treatment for Lumbar Spinal Tuberculosis

OBJECTIVE

To compare the clinical outcome between bilateral percutaneous endoscopic debridement and lavage (PEDL) and unilateral PEDL treatment for lumbar spine tuberculosis (LST).

METHODS

A total of 40 patients with LST who underwent either bilateral PEDL (group A) or unilateral PEDL (group B) were reviewed. Perioperative parameters were assessed by operative time, intraoperative fluoroscopy times, and days of postoperative continuous irrigation and vacuum drainage. Clinical outcomes were evaluated in the Oswestry Disability Index (ODI), visual analog scale (VAS), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP). All patients were followed-up for at least 18 months after treatment.

RESULTS

The average operative time and intraoperative fluoroscopy time were increased in group A compared with those in group B. There was no statistical significance between the 2 groups in postoperative continuous irrigation and vacuum drainage days. The ESR and CRP curves in the 2 groups showed a similar trend during 18-month follow-up. The VAS and ODI in the 2 groups significantly decreased 6 and 18 months postsurgery. There was no significant difference in the incidence of complication between the 2 groups.

CONCLUSIONS

Two procedures yielded comparable and satisfactory results. Unilateral PEDL showed shorter operative time and decreased intraoperative fluoroscopy times compared with bilateral PEDL. We suggest the use of unilateral PEDL rather than bilateral PEDL in the treatment of LST.

Systemic and pulmonary C1q as biomarker of progressive disease in experimental non-human primate tuberculosis

Tuberculosis (TB) causes 1.6 million deaths annually. Early differential diagnosis of active TB infection is essential in optimizing treatment and reducing TB mortality, but is hampered by a lack of accurate and accessible diagnostics. Previously, we reported on complement component C1q, measured in serum by ELISA, as a candidate biomarker for active tuberculosis. In this work we further examine the dynamics of C1q as a marker of progressive TB disease in non-human primates (NHP). We assessed systemic and pulmonary C1q levels after experimental infection using high or low single dose as well as repeated limiting dose Mycobacterium tuberculosis (Mtb) challenge of macaques. We show that increasing C1q levels, either peripherally or locally, correlate with progressive TB disease, assessed by PET-CT imaging or post-mortem evaluation. Upregulation of C1q did not precede detection of Mtb infection by a conventional interferon-gamma release assay, confirming its association with disease progression. Finally, pulmonary vaccination with Bacillus Calmette Guérin also increased local production of C1q, which might contribute to the generation of pulmonary protective immunity. Our data demonstrate that NHP modelling of TB can be utilized to study the role of C1q as a liquid biomarker in TB protection and disease, complementing findings in TB patients.

Multicenter feasibility study to assess external quality panels for molecular diagnostics for tuberculosis in China

The roll-out of molecular diagnostic tools continues to be the most important shift in the tuberculosis diagnostic landscape. The aim of this study was to develop a novel external quality assessment (EQA) panels for molecular TB diagnostics. In addition, we also assessed the performance of the laboratories with the EQA panels in China. Dried Mycobacterium tuberculosis (MTB) DNA in the chelex resin was designed as part of an EQA program. The storage of genomic DNA in the chelex resin layer had no effect on the stability of genomic DNA, even after 12 weeks of storage. Seventy-one laboratories have participated in EQA of molecular diagnostics for TB diagnosis in 2018. GeneXpert (74.6%, 53/71) was the most predominant molecular method, followed by GeneChip (32.3%, 23/71), MeltPro (22.5%, 16/71), and TB-LAMP (7.0%, 5/71). Out of 105 EQA panels, 103 EQA results (98.1%) achieved perfect scores, whereas the other two (1.9%) had satisfactory scores. There were a total of two false-negative results reported from two laboratories with local LAMP, respectively. In conclusion, we firstly develop feasible EQA panels for molecular diagnostics for tuberculosis in China. Our data demonstrate that a majority of participating laboratories are able to produce perfect results with molecular diagnostics in China, giving us important hints for the implementation of molecular diagnostics.

Factors Associated with Health-Seeking Preference Among People Who Were Supposed to Cough for More Than 2 Weeks: A Cross-Sectional Study in Southeast China

BACKGROUND

The health-seeking preference of people with a cough >2 weeks had not been extensively researched in southeast China. The study aimed to explore factors associated with health-seeking preference, which could provide more evidence to improve individuals' appropriate health-seeking behavior.

MATERIALS AND METHODS

From October 2018 to December 2018, this cross-sectional study was conducted in Zhejiang, China. A questionnaire was used to collect information on sociodemographic characteristics, knowledge of tuberculosis (TB), and health-seeking preference. The chi-square test and multivariable logistic regression were performed to evaluate factors associated with health-seeking preference.

RESULTS

Of the 7174 participants, 3321 (46.3%) were men, 6148 (85.7%) were married, and 6013 (83.8%) knew about TB. Appropriate health-seeking preference was reported by 6229 (86.8%) participants. Respondents knowing about TB were more likely to seek appropriate care than those did not (89.6% vs 72.4%, p<0.001). Of the 6013 participants knowing about TB, respondents with higher scores on five key items of TB knowledge were more likely to get appropriate health-seeking preference. About 805 (96.6%) participants with 5 scores on TB knowledge had appropriate care preference. Only 97 (72.4%) participants with a score of 0 reported an appropriate preference. Multivariable logistic regression showed residence, marital status, education level, occupation, and awareness of TB knowledge were predictors of appropriate health-seeking preference. Compared to participants with a score of 0 on five TB key knowledge, participants with a score of 5 were 8.57 times more likely to have appropriate health-seeking preference (95% confidence interval [CI]: 4.97-14.78), followed by a score of 4 (odds ratio [OR]=5.99, 95% CI, 3.23-8.03); 3 (OR=3.74, 95% CI, 2.44-5.74); 2 (OR=1.99, 95% CI, 1.30-3.02) and 1 (OR=1.17, 95% CI, 0.76-1.80).

CONCLUSION

Participants with little knowledge of TB had a low level of appropriate health-seeking preference. Appropriate health-seeking preference of the participants improved with increased key knowledge level of TB.

Tuberculosis Transmission in a Primary School and a Private Language School. An Estimation of Infectivity

Introduction: Belgium is a country with low incidence of tuberculosis (TB) and a very low number of TB cases in children. Children in contact with an adult smear-positive TB case are at high risk of transmission. Early diagnosis is important as young children have a significant predisposition of developing TB disease. In this paper, we describe two outbreaks after exposure to, respectively, two teachers with smear-positive pulmonary TB: one in a primary school, a nursery teacher, and another in a private language school. Methods: An exposure investigation was carried out in both index cases household and school, according to the stone-in-the-pond principle. The tuberculin skin test (TST) was used a screening tool. The time elapsed between TB diagnosis in the index case and contact investigation was, respectively, 1 and 3 weeks. If this initial test was negative, it was repeated after a "window period" of ≥8 weeks. Results: Index cases showed a transmission rate of, respectively, 13 and 40% in their classes at school, defined as casual contacts. The proximity of contact increased the risk of infection. TB disease was observed in, respectively, 4 and 11% of all the casual contacts; all of them were children younger than 5 years old. TB-infected and children with active TB disease had good compliance with recommended treatment. Uptake of chemoprophylaxis during the "window period" was poor, respectively, only 32-42%, in children under 5 years with an initially negative TST. Discussion: The World Health Organization recommends to screen all young children (<5 years old) who have close contact with a person affected by pulmonary TB and to initiate Latent tuberculosis infection treatment even before infection can be demonstrated, after ruling out active TB disease. Despite this knowledge, a small percentage of the children younger than 5 years with no proof of infection was treated with the proposed chemoprophylactic treatment, in both cases. Conclusion: This exposure investigation of two teachers detects high transmission among family contacts and school casual contacts. Recommendations for chemoprophylactic treatment in children <5 years showed low compliance, reflecting the difficulty of communication to staff, parents, and children in a school outbreak. It is essential to develop a new approach for this vulnerable group of patients. This approach could be improved, applied, and evaluated by National TB Control Programs, involving public and private health services. Public health authorities play a role in raising public awareness about the risks of TB for young children.

Sniffing animals as a diagnostic tool in infectious diseases

BACKGROUND

Scents and odours characterize some microbes when grown in the laboratory, and experienced clinicians can diagnose patients with some infectious diseases based on their smell. Animal sniffing is an innate behaviour, and animals' olfactory acuity is used for detecting people, weapons, bombs, narcotics and food.

OBJECTIVES

We briefly summarized current knowledge regarding the use of sniffing animals to diagnose some infectious diseases and the potential use of scent-based diagnostic instruments in microbiology.

SOURCES

Information was sought through PubMed and extracted from peer-reviewed literature published between January 2000 and September 2019 and from reliable online news. The search terms 'odour', 'scent', 'bacteria', 'diagnostics', 'tuberculosis', 'malaria' and 'volatile compounds' were used.

CONTENT

Four major areas of using sniffing animals are summarized. Dogs have been used to reliably detect stool associated with toxigenic Clostridioides difficile and for surveillance. Dogs showed high sensitivity and moderate specificity for detecting urinary tract infections in comparison to culture, especially for Escherichia coli. African giant pouched rats showed superiority for diagnosing tuberculosis over microscopy, but inferiority to culture/molecular methods. Several approaches for detecting malaria by analysing host skin odour or exhaled breath have been explored successfully. Some microbial infections produce specific volatile organic compounds (VOCs), which can be analysed by spectrometry, metabolomics or other analytical approaches to replace animal sniffing.

IMPLICATIONS

The results of sniffing animal studies are fascinating, and animal sniffing can provide intermediate diagnostic solutions for some infectious diseases. Lack of reproducibility, and cost of animal training and housing are major drawbacks for wider implementation of sniffing animals. The ultimate goal is to understand the biological background of this animal ability and to characterize the specific VOCs that animals are recognizing. VOC identification, improvement of odour sampling methods and development of point-of-care instruments could allow implementation of scent-based tests for major human pathogens.

Defining a migrant-inclusive tuberculosis research agenda to end TB

BACKGROUND

Pillar 3 of the End TB Strategy calls for the promotion of research and innovation at the country level to facilitate improved implementation of existing and novel interventions to end tuberculosis (TB). In an era of increasing cross-border migration, there is a specific need to integrate migration-related issues into national TB research agendas. The objective of the present review is to provide a conceptual framework to guide countries in the development and operationalization of a migrant-inclusive TB research agenda.

METHODS

We conducted a literature review, complemented by expert opinion and the previous articles in this State of the Art series, to identify important themes central to migration-related TB. We categorized these themes into a framework for a migration-inclusive global TB research agenda across a comprehensive spectrum of research. We developed this conceptual framework taking into account: 1) the biomedical, social and structural determinants of TB; 2) the epidemiologic impact of the migration pathway; and 3) the feasibility of various types of research based on a country's capacity.

DISCUSSION

The conceptual framework presented here is based on the key principle that migrants are not inherently different from other populations in terms of susceptibility to known TB determinants, but that they often have exacerbated or additional risks related to their country of origin and the migration process, which must be accounted for in developing comprehensive TB prevention and care strategies. A migrant-inclusive research agenda should systematically consider this wider context to have the highest impact.

Is rifampin resistance a reliable predictive marker of multidrug-resistant tuberculosis in China: A meta-analysis of findings

OBJECTIVES

Systematic review of multidrug-resistant tuberculosis (MDR-TB) prevalence among rifampicin (RIF)-resistant tuberculosis (RR-TB) patients in 34 provinces of China was conducted to correlate RIF resistance with concurrent isoniazid (INH) resistance.

METHODS

Database searches (PubMed, Embase, China National Knowledge Infrastructure, Chinese Scientific Journal, Wanfang), identified drug resistance surveillance studies conducted between January 1, 2000 and June 30, 2018. Of 1554 records, random-effects meta-analysis of 34 studies of adequate methodological quality yielded 108,366 TB cases for MDR-TB prevalence analysis of RR-TB cases.

RESULTS

MDR-TB prevalence among RR-TB cases varied from 57% (Xinjiang; 95% CI 47%, 67%) to 95% (Taiwan; 95% CI 92%, 98%), for a pooled national rate of 77% (95% CI 75%, 80%). Subgroup and meta-regression analyses revealed greater MDR-TB prevalence in previously treated versus new RR-TB cases (P < 0.001), with no significant differences of regional initial drug resistance rates or sampling methods. Regional MDR-TB prevalence among RR-TB cases was lowest (69%) in the Northeast Region (95% CI 65%, 73%) and highest (90%) in Hong Kong, Macao and Taiwan (95% CI 81%, 98%).

CONCLUSIONS

In China, ∼77% of RR-TB cases are MDR-TB. Thus, RIF resistance cannot effectively predict MDR-TB. Highly variable RR-TB prevalence across China warrants improved TB management.

Informing decision-making for universal access to quality tuberculosis diagnosis in India: an economic-epidemiological model

BACKGROUND

India and many other high-burden countries have committed to providing universal access to high-quality diagnosis and drug susceptibility testing (DST) for tuberculosis (TB), but the most cost-effective approach to achieve this goal remains uncertain. Centralized testing at district-level hub facilities with a supporting sample transport network can generate economies of scale, but decentralization to the peripheral level may provide faster diagnosis and reduce losses to follow-up (LTFU).

METHODS

We generated functions to evaluate the costs of centralized and decentralized molecular testing for tuberculosis with Xpert MTB/RIF (Xpert), a WHO-endorsed test which can be performed at centralized and decentralized levels. We merged the cost estimates with an agent-based simulation of TB transmission in a hypothetical representative region in India to assess the impact and cost-effectiveness of each strategy.

RESULTS

Compared against centralized Xpert testing, decentralization was most favorable when testing volume at decentralized facilities and pre-treatment LTFU were high, and specimen transport network was exclusively established for TB. Assuming equal quality of centralized and decentralized testing, decentralization was cost-saving, saving a median $338,000 (interquartile simulation range [IQR] - $222,000; $889,000) per 20 million people over 10 years, in the most cost-favorable scenario. In the most cost-unfavorable scenario, decentralized testing would cost a median $3161 [IQR $2412; $4731] per disability-adjusted life year averted relative to centralized testing.

CONCLUSIONS

Decentralization of Xpert testing is likely to be cost-saving or cost-effective in most settings to which these simulation results might generalize. More decentralized testing is more cost-effective in settings with moderate-to-high peripheral testing volumes, high existing clinical LTFU, inability to share specimen transport costs with other disease entities, and ability to ensure high-quality peripheral Xpert testing. Decision-makers should assess these factors when deciding whether to decentralize molecular testing for tuberculosis.

Human Antimicrobial RNases Inhibit Intracellular Bacterial Growth and Induce Autophagy in Mycobacteria-Infected Macrophages

The development of novel treatment against tuberculosis is a priority global health challenge. Antimicrobial proteins and peptides offer a multifaceted mechanism suitable to fight bacterial resistance. Within the RNaseA superfamily there is a group of highly cationic proteins secreted by innate immune cells with anti-infective and immune-regulatory properties. In this work, we have tested the human canonical members of the RNase family using a spot-culture growth inhibition assay based mycobacteria-infected macrophage model for evaluating their anti-tubercular properties. Out of the seven tested recombinant human RNases, we have identified two members, RNase3 and RNase6, which were highly effective against Mycobacterium aurum extra- and intracellularly and induced an autophagy process. We observed the proteins internalization within macrophages and their capacity to eradicate the intracellular mycobacterial infection at a low micro-molar range. Contribution of the enzymatic activity was discarded by site-directed mutagenesis at the RNase catalytic site. The protein induction of autophagy was analyzed by RT-qPCR, western blot, immunofluorescence, and electron microscopy. Specific blockage of auto-phagosome formation and maturation reduced the protein's ability to eradicate the infection. In addition, we found that the M. aurum infection of human THP1 macrophages modulates the expression of endogenous RNase3 and RNase6, suggesting a function in vivo. Overall, our data anticipate a biological role for human antimicrobial RNases in host response to mycobacterial infections and set the basis for the design of novel anti-tubercular drugs.