Classification of early tuberculosis states to guide research for improved care and prevention: an international Delphi consensus exercise

Evaluating stratified T-SPOT.TB results for diagnostic accuracy in tuberculosis disease: a retrospective cohort study with sensitivities, specificities, and predictive values

OBJECTIVES

The study aimed to investigate the association between quantitative T-SPOT.TB values and the risk of incident and prevalent tuberculosis disease (TBD), identify risk factors, and evaluate test accuracy.

METHODS

This retrospective cohort study followed patients tested consecutively with T-SPOT.TB at Aarhus University Hospital from 2010 to 2017, with follow-up for incident TBD through 2022. Data on demographics, comorbidities, medications, and TB status were collected from patient records and national registries. Cox proportional hazard models with restricted cubic splines assessed the risk of incident TBD (occurring ≥3 months post-test) by quantitative spot counts. Cox and log-binomial regressions identified risk factors for incident and prevalent TBD (occurring between 3 months before and after the test). Sensitivity, specificity, and predictive values assessed test accuracy. T-SPOT.TB was the index test, and microbiologically and/or clinically confirmed TBD was the reference standard.

RESULTS

Among 8542 individuals with complete follow-up, 59 developed incident TBD over 67 456 person-years. Among 9014 individuals tested once, 162 had prevalent TBD at the time of testing. The risk of incident TBD increased with higher spot counts, plateauing for tests with more than ten spots. The strongest risk factors for both incident and prevalent TBD were categorical T-SPOT.TB results: compared with negative tests (≤4 spots), adjusted hazard ratios for incident TBD were 5.0 (95% CI: 1.9-13.1) for borderline (5-7 spots) and 8.0 (95% CI: 4.0-15.7) for positive tests (≥8 spots). Adjusted risk ratios for prevalent TBD were 14.9 (95% CI: 7.7-28.9) for borderline and 35.6 (95% CI: 21.4-59.2) for positive tests. Sensitivities for incident and prevalent TBD were 54.0% (95% CI: 39.3-68.2%) and 78.4% (95% CI: 71.3-84.5%), respectively. Specificities were 84.8 (84.0-85.4) and 83.7 (82.9-84.4), respectively.

DISCUSSION

Incident TBD risk increases with T-SPOT.TB values but plateaus beyond 10 spots. Borderline and positive T-SPOT.TB results are strongly linked to TBD risk.

Discordance between measures of Mycobacterium tuberculosis sensitization and type 2 diabetes mellitus in the United States (NHANES): a population-based cohort study

OBJECTIVE

We examined how latent TB infection (LTBI), evaluated by cell-mediated immune responses to Mycobacterium tuberculosis (Mtb) antigens, impacts glucose metabolism in US adults.

METHODS

Mtb sensitization was evaluated by interferon-γ (IFN-γ) release assay (IGRA+: assay reactivity) and tuberculin skin testing (TST+: skin induration ≥10mm), and categorized as: IGRA-/TST- (TB uninfected controls); IGRA-/TST+; IGRA+/TST-; or IGRA+/TST+. Diabetes was ascertained by fasting plasma glucose (FPG) ≥7.0mmol/L, HbA1c ≥6.5% and/or antidiabetic medication. Adjusted generalized additive models examined nonlinear effects of skin induration and IFN-γ reactivity on FPG and HbA1c; and LTBI on diabetes prevalence.

RESULTS

Among 1,787 (IGRA-/TST-), 101 (IGRA-/TST+), 92 (IGRA+/TST-), and 99 (IGRA+/TST+) adults, skin induration linearly associated with FPG [effective degrees of freedom (EDF) =1.01; p<0.001] and non-linearly with HbA1c [EDF=1.76; p=0.003]. IFN-γ reactivity correlated with neither FPG [p=0.58] nor HbA1c [p=0.94]. Relatedly, adjusted diabetes prevalence was greater in IGRA-/TST+ [24.9%; p=0.048] and IGRA+/TST+ [27.3%; p=0.004] but not IGRA+/TST- [15.9%; p=0.69] individuals than among controls [15.3%].

CONCLUSIONS

LTBI associated with glycemic measures and diabetes when assessed by skin induration, but not IFN-γ release. This suggests an association with innate immune activation rather than acquired T-cell response, as determined by ex vivo IFN-γ release assay.

CD8α marks a Mycobacterium tuberculosis-reactive human NK cell population with high activation potential

Natural Killer (NK) cells can recognize and kill Mycobacterium tuberculosis (Mtb)-infected cells in vitro, however their role after natural human exposure has not been well-studied. To identify Mtb-responsive NK cell populations, we analyzed the peripheral blood of healthy household contacts of active Tuberculosis (TB) cases and source community donors in an endemic region of Port-au-Prince, Haiti by flow cytometry. We observed higher CD8α expression on NK cells in putative resistors (Interferon γ release assay negative; IGRA- contacts) with a loss of CD8α surface expression during household-associated exposure and active TB disease. In vitro assays and CITE-seq analysis of CD8α+ NK cells demonstrated enhanced maturity, cytotoxic gene expression, and response to cytokine stimulation relative to CD8α- NK cells. CD8α+ NK cells also displayed dynamic surface expression dependent on MHC class I in contrast to conventional CD8+ T cells. Together, these results support a specialized role for CD8α+ NK cell populations during Mtb infection correlating with disease resistance.

Subclinical disease among people with culture-confirmed pulmonary tuberculosis in Singapore - a retrospective study

OBJECTIVES

Subclinical tuberculosis (TB) is challenging to diagnose due to the lack of a clear definition and symptoms. This study aimed to describe the subclinical disease spectrum among people with culture-confirmed pulmonary TB routinely diagnosed in Singapore, a country with moderate incidence, using different definitions. It also aimed to identify risk factors for subclinical TB and the current diagnostic approaches in detecting subclinical TB.

METHODS

A retrospective analysis of sputum culture-positive pulmonary TB cases reported to the Singapore National TB Registry from January 1, 2004 to December 31, 2023 was conducted. Two definitions for subclinical TB were used: sputum culture-positive TB with no cough or cough for less than 2 weeks for definition 1 and no cough for definition 2.

RESULTS

Of 18,693 pulmonary TB cases notified, 41.6% and 31.6% met the first and second definition of subclinical TB, respectively. However, neither definition performed better in detecting subclinical TB (receiver operating characteristics curve). The majority of cases (96.7% and 96.0% respectively) had abnormal chest X-ray findings, and a high proportion had smear-positive results (40.0% and 35.6%, respectively). Sputum TB polymerase chain reaction (PCR) was significant in picking up subclinical TB adjusted odds ratio 1.20 (95% confidence interval 1.10-31), although 42.2% with no persistent cough and 41.2% with no cough did not have sputum TB PCR tested, highlighting gaps in diagnostic practices. Together, older adults (aged ≥70 years) and immunocompromised individuals, including those with end-stage renal failure, steroid therapy, malignancy, and HIV, were more likely to have subclinical TB.

CONCLUSIONS

Our study suggests that subclinical TB are more likely to occur in those older than 70 years and those with immunocompromising conditions. The use of diagnostics such as chest X-ray and sputum TB PCR are helpful in diagnosing subclinical TB. Further research is necessary to evaluate other screening tools in detecting these early disease states.

Insights into protection against Mycobacterium tuberculosis infection: time to officially confirm another phenotype?

Immune correlates of protection against infection with Mycobacterium tuberculosis (Mtb) remain elusive. In this issue of the JCI, Dallmann-Sauer and authors demonstrate that lack of tuberculin skin test (TST) and interferon γ release assay (IGRA) conversion among people with HIV despite years-long Mtb exposure is associated with alveolar lymphocytosis, including specific poly-cytotoxic T cells, and M1-type alveolar macrophages with a stronger ex vivo response to the pathogen. Studies in these rare individuals, termed "TB resisters" and in tuberculosis household contacts who are repeatedly IGRA negative in the months after a specific exposure event (known as "early clearers") help elucidate manipulatable mechanisms to boost protection against Mtb infection.

Diagnostic accuracy of smear microscopy, mycobacterial culture, and GeneXpert MTB/RIF assay for diagnosis of subclinical tuberculosis: a retrospective multicenter study

Subclinical tuberculosis (TB) challenges public health interventions. This retrospective multicenter study aimed to evaluate the diagnostic efficacy of smear microscopy, mycobacterial culture, and GeneXpert MTB/RIF assay (Xpert) for subclinical TB and identify its proportion and risk factors in China. Among 560 participants diagnosed with TB, 309 (55.18%) patients had active TB, and 251 (44.82%) had subclinical TB. For subclinical TB diagnosis, smear microscopy, mycobacterial culture, and Xpert had detection rates of 11.5%, 40.6%, and 40.6%, respectively, which were significantly lower than those for active TB (25.2%, 59.2%, and 63.7% respectively). Conversely, interferon-γ release assays (IGRA) showed similar detection rates for both subclinical (85.7%) and active TB (84.1%). Age groups of 40-60 years and under 40 years, as well as employed individuals had higher risks of subclinical TB. To conclude, about 45% of TB patients were subclinical in our study. Microbiologic tests had lower diagnostic sensitivities for subclinical TB than for active TB, while IGRA positivity rates were comparable between asymptomatic and symptomatic TB patients, highlighting the potential of antigen-specific immune response in the diagnosis of these asymptomatic individuals. Further clinical trials are warranted to investigate the diagnostic flow chart in individuals with subclinical TB.

IMPORTANCE

Subclinical tuberculosis (TB) poses a major challenge to public health interventions, especially in the wake of the COVID-19 pandemic. However, a substantial proportion of individuals have absence or non-recognized symptoms, which put great pressure on clinical diagnosis. In this study, we conducted a retrospective multicenter study to assess the performance of smear microscopy, mycobacterial culture, and GeneXpert MTB/RIF (Xpert) in diagnosis of subclinical TB. We also aimed to determine the proportion and risk factors of subclinical TB in China in order to accelerate progress towards global milestones and targets for the End TB Strategy.

Ecology, global diversity and evolutionary mechanisms in the Mycobacterium tuberculosis complex

With the COVID-19 pandemic receding, tuberculosis (TB) is again the number one cause of human death to a single infectious agent. TB is caused by bacteria that belong to the Mycobacterium tuberculosis complex (MTBC). Recent advances in genome sequencing have provided new insights into the ecology and evolution of the MTBC. This includes the discovery of new phylogenetic lineages within the MTBC, a deeper understanding of the host tropism among the various animal-adapted lineages, enhanced knowledge on the evolutionary dynamics of antimicrobial resistance and transmission, as well as a better grasp of the within-host MTBC diversity. Moreover, advances in long-read sequencing are increasingly highlighting the relevance of structural genomic variation in the MTBC. These findings not only shed new light on the biology and epidemiology of TB, but also give rise to new questions and research avenues. The purpose of this Review is to summarize these new insights and discuss their implications for global TB control.

Tuberculosis preventive therapy: scientific and ethical considerations for trials of ultra-short regimens

Preventive therapy remains key to the elimination of tuberculosis and is typically offered to people with presumptive Mycobacterium tuberculosis infection to prevent active disease. Although the duration of tuberculosis preventive therapy has been reduced substantially over time, it remains long in absolute terms, and uptake remains low. Treatment-shortening trials using non-inferiority designs have so far led to the implementation of effective regimens of 1-4 months' duration. Such regimens are a substantial improvement on the previous 6-9 months' duration standard of care but still far too long given potential toxicity and the very low baseline risk of disease for most individuals. The efficacy of even shorter tuberculosis preventive therapy regimens, including ultra-short regimens shorter than 2 weeks' duration, is yet to be explored, but optimal public health outcomes might be achieved even if the efficacy of such regimens is lower than that of the standard of care. Greater acceptability could lead to higher population uptake, and, potentially, to more cases of tuberculosis avoided. Nonetheless, the optimal duration of ultra-short tuberculosis preventive therapy regimens cannot be explored through classic two-arm non-inferiority trials. Instead, the relationship between different durations and efficacy of tuberculosis preventive therapy will need to be characterised, requiring some participants to be randomly assigned to no (or delayed) therapy in order to characterise the number of tuberculosis cases averted by the shortest options. We argue that such trials are needed to identify the optimal trade-off between efficacy and acceptability and would be ethically acceptable provided there were appropriate risk mitigation measures for participants, including careful monitoring for the development of active disease. In this Personal View, we discuss some of the scientific and ethical considerations around the investigation of ultra-short-course preventive therapy for tuberculosis.

Brazilian recommendations for the management of tuberculosis infection in immune-mediated inflammatory diseases

BACKGROUND

The risk of tuberculosis infection (TBI) and its progression to tuberculosis disease (TBD) among persons with immune-mediated inflammatory diseases (IMID) results from a complex interplay of patient and disease characteristics, immunosuppression level, and the epidemiological context. Brazilian recommendations are unclear about TBI screening and its preventive treatment (TPT) in persons with IMID.

OBJECTIVE

To provide a comprehensive and evidence-based guideline for managing TBI in persons with IMID in Brazil.

METHODS

This task force was constituded by 42 specialists with interest in IMID and TBD. A core leadership team (CLT) drafted fourteen clinical questions on the risk of tuberculosis and indications of TPT among persons with IMID who started, or are about to start immunosuppressive drugs. The CLT supervised the systematic reviews and formulated the recommendations. The experts voted using the Delphi Method.

RESULTS

Nine recommendations were established. More than 80% of panelists voted "agree" and "strongly agree" with all statements. In brief, all persons with IMID starting or about to start immunosuppressive treatment should undergo tuberculin skin testing (TST) or interferon-gamma release assays (IGRAs), a chest imaging test and investigation of contact with active pulmonary or laryngeal TBD. TPT is mandatory for those with any positive result after excluding TBD. Exceptions include individuals with a history of TBD or a past positive TBI infection test. IGRA is preferred only in persons BCG-vaccinated in the past 2 years. Those with inconclusive IGRA results can have the test repeated once, and TPT should be offered if it remains indeterminate. TST or IGRA should be repeated yearly, for three years, when the previous test was negative, when starting or changing to a different class of immunosuppressive drug. Overall, the included studies had a low quality of evidence and high risk of bias.

CONCLUSIONS

These guidelines are meant to improve the management of TBI in IMID. Health professionals must consider the epidemiological risk, host features, the social scenario, the characteristics of the disease, the access to health resources, and the development of an individualized plan for every patient.

The long-term risk of tuberculosis among individuals with Xpert Ultra "trace" screening results: a longitudinal follow-up study

Background

Systematic screening for tuberculosis using Xpert Ultra generates "trace" results of uncertain significance. Additional microbiological testing in this context is often negative, but individuals with trace results might have early disease or elevated risk of tuberculosis.

Methods

We screened for tuberculosis with Xpert Ultra in Uganda, enrolling individuals with trace-positive results and Ultra-negative controls. Participants without tuberculosis on extensive initial evaluation were followed, with repeat testing at 1, 3, and 6 months after trace results, and at 12 and 24 months for all participants. We estimated cumulative cause-specific hazards of incident tuberculosis, considering a definition of tuberculosis that included clinician judgment and one based strictly on microbiological results. We compared participants with Ultra-trace versus Ultra-negative sputum, and subgroups of participants with Ultra-trace sputum.

Findings

Of 129 participants with trace-positive screening results, 45 (35%) were recommended for treatment upon enrollment, and eight were lost to follow-up within three months. Of 76 remaining participants followed for median 697 (interquartile range 179-714) days, 20 (26%) were recommended for tuberculosis treatment. The cumulative hazard of clinician-defined incident tuberculosis was 26% (95% confidence interval: 14-38%) at one year and 35% (19-52%) at two years, versus 2% (0-5%) at two years for controls. Hazards were similar for microbiologically defined incident tuberculosis. Incident tuberculosis was strongly associated with abnormal baseline chest X-ray (hazard ratio 15.0 [3.4-65.1]) but not with baseline symptoms.

Interpretation

Individuals with trace-positive sputum during screening, particularly those with abnormal chest imaging, are at substantial risk of incident tuberculosis over the subsequent two years.

Funding

National Institutes of Health.

Diagnostic tests for tuberculosis infection and predictive indicators of disease progression: Utilizing host and pathogen biomarkers to enhance the tuberculosis elimination strategies

Tuberculosis (TB) remains the leading cause of death worldwide from a single infectious disease. An estimated quarter of the world's population, about 2 billion people, has an immune response to Mycobacterium tuberculosis (Mtb) without clinical, microbiological, or radiological signs of TB disease. This condition is known as TB infection (TBI) and carries a lifelong risk of reactivation with 5%-10% of individuals eventually developing TB disease during their lifetime. Interferon-γ release assay and skin-tests are World Health Organization (WHO)-approved tests for TBI diagnosis and allow to identify those needing TB preventive therapy. The WHO End TB Strategy proposes several approaches to mitigate the global burden of TB. Achieving the goal of TB elimination requires improved early diagnosis of TBI individuals at risk of developing TB disease, provision of preventive therapy, and development of new diagnostic tests to address the current limitations. This review provides an update on the tests currently used for TBI diagnosis and offers an overview of experimental tests based on either host response analysis or pathogen detection. Additionally, we briefly report experimental tests, such as those based on host RNA signatures, which can help identifying TBI individuals at high risk of progressing toward TB disease. Although these experimental tests show promise, further investigation and randomized clinical trials are required to establish reliable proof-of-concept.

Tuberculosis and HIV coinfection: Progress and challenges towards reducing incidence and mortality

HIV-associated tuberculosis (HIV-TB) is associated with disproportionate mortality: approximately 24% of the 660,000 individuals with TB and HIV died, compared to 11% of those without HIV dying from TB in 2023. HIV is a key driver of ongoing high TB incidence in many countries, particularly in the World Health Organization Africa region, and TB is the leading cause of hospitalization in people with HIV (PWH) globally. Significant developments have occurred recently concerning the prevention, screening, diagnosis, and management of HIV-TB. Antiretroviral therapy and novel regimens for TB preventive therapy are now known to decrease TB incidence and improve survival. The use of Xpert Ultra (Cepheid, USA) and urine DetermineTM TB LAM Antigen (Abbott, USA) as diagnostics are associated with improved survival for HIV-TB. However, there are ongoing gaps in our knowledge: regarding the natural history of TB disease in PWH; optimal approaches to diagnosis of TB and TB drug resistance including in non-sputum samples; and post-TB disease in PWH. We discuss recent progress, together with ongoing challenges towards reducing incidence, morbidity, and mortality. We highlight ongoing research that will advance our understanding and management of HIV-TB: including vaccine research, novel treatment strategies, and expanded options for the diagnosis of TB and drug resistance in PWH.

Gallbladder and liver miliary nodules: a surprising diagnosis of disseminated tuberculosis during emergency laparoscopic cholecystectomy

BACKGROUND

Disseminated tuberculosis (TB) presenting as miliary nodules on the gallbladder and liver is extremely rare and poses significant diagnostic challenges. This report describes a case of disseminated TB discovered during emergency laparoscopic cholecystectomy for acute cholecystitis.

CASE PRESENTATION

A 77-year-old male presented with decreased appetite, weight loss, and fever. Preoperative imaging suggested gallstones and cholecystitis. During surgery, multiple miliary nodules were found on the surfaces of the gallbladder and liver, raising suspicion of metastatic cancer. Intraoperative frozen pathology revealed epithelioid granulomas with necrosis, and postoperative molecular testing confirmed Mycobacterium tuberculosis.

CONCLUSIONS

This case highlights the importance of considering TB in the differential diagnosis of intra-abdominal nodules, especially in TB-endemic regions. Intraoperative frozen pathology and molecular diagnostics are crucial for timely and accurate diagnosis.

Pulmonary Tuberculosis Infectiousness of Persons Identified Through Active and Passive Case-finding in a High-burden Setting

Background

The role of active case-finding (ACF) in improving tuberculosis (TB) prevention and care depends on the infectiousness of persons with undiagnosed TB and the accuracy of screening strategies. To compare undiagnosed community dwellers to persons presenting for healthcare, we evaluated clinicodemographic and microbiologic characteristics, cough aerosol culture (CAC) status, and household contact (HHC) QuantiFERON-Plus (QFT) status by case-finding approach in adults with pulmonary TB.

Methods

We enrolled 388 Kenyan adults with GeneXpert (excluding trace) and/or culture-confirmed, untreated TB through healthcare presentation (passive case-finding [PCF]; 87%) or ACF (community-based prevalence survey). Interventions included cough aerosol sampling and HHC QFT testing. We performed mixed-effect logistic regression to predict transmission, clustered on index participants.

Results

World Health Organization-recommended screening symptoms (W4SS) were more common in the PCF cohort (99% vs 73%, P < .001). Traditional makers of infectiousness were less frequent in the ACF cohort. Higher symptom burden (number of reported World Health Organization-recommended 4-symptom screen) associated with higher bacillary burden (lower GeneXpert Ct) (estimate -0.55; 95% confidence interval [CI], -.98 to -.13; P = .01). Among 263 participants with CAC, 21% were CAC-positive, none of whom enrolled through ACF. Among 270 HHCs, QFT positivity differed by index CAC status (89% vs 56% in HHCs of CAC-positive and negative participants, respectively; P < .001) but not by traditional infectiousness makers or case-finding approach. Index CAC-positive status (adjusted odds ratio [aOR], 11.2; CI, 2.2-58.3), HIV-positive status (aOR, 0.1; CI, .0-.6), and HHCs age (aOR, 1.04; CI, 1.01-1.08), independently predicted HHC QFT positivity.

Conclusions

Our findings suggest that ACF may detect a smaller proportion of CAC-positive persons with TB than PCF.

Tuberculosis: An Update for the Clinician

Tuberculosis (TB) remains a significant global health threat with high mortality and efforts to meet WHO End TB Strategy milestones are off-track. It has become clear that TB is not a dichotomous infection with latent and active forms but presents along a disease spectrum. Subclinical TB plays a larger role in transmission than previously thought. Aerosol studies have shown that undiagnosed TB patients, even with paucibacillary disease, can be highly infectious and significantly contribute to TB spread. Encouraging clinical results have been seen with the M72/AS01E vaccine. If preliminary results can be confirmed in ongoing larger trials, modelling shows the vaccine can positively impact the epidemic. TB preventive therapy (TPT), especially for high-risk groups like people living with HIV and household contacts of drug-resistant TB patients, has shown efficacy but implementation is resource intensive. Treatment options for infectious patients have grown rapidly. New shorter, all-oral treatment regimens represent a breakthrough, but progress is threatened by rising resistance to bedaquiline. Many new chemical entities are entering clinical trials and raise hopes for all-new regimens that could overcome rising resistance rates to conventional agents. More research is needed on the management of complex cases, such as central nervous system TB and severe HIV-associated TB. Post-TB lung disease (PTLD) is an under-recognised but growing concern, affecting millions of survivors with lasting respiratory impairment and increased mortality. Continued investment in development of TB vaccines and therapeutics, treatment shortening, and management of TB sequelae is critical to combat this ongoing public health challenge.

Assessment and management for latent tuberculosis before advanced therapies for immune-mediated inflammatory diseases: A comprehensive review

Tuberculosis (TB), caused by Mycobacterium tuberculosis , is the most significant infectious cause of mortality across the globe. While TB disease can prey on immunocompetent individuals, it is more likely to occur in immunocompromised individuals. Immune-mediated inflammatory diseases (IMIDs) are a group of diseases (rheumatoid arthritis, inflammatory bowel disease, ankylosing spondylitis, psoriasis, hidradenitis suppurativa, autoimmune blistering diseases, and others) where there may be a need for systemic immunosuppression to control the disease manifestations, treat symptoms and improve long term outcomes. Immunosuppression may predispose them to active TB either from recent infection or reactivation of Latent TB (LTB). The major determinants of reactivation include the type of therapy (highest risk with TNF inhibitors and JAK inhibitors) and the underlying TB endemicity. The strategy to avoid TB reactivation includes the detection of LTB using tests that detect immunoreactivity to TB antigens (interferon-gamma release assays or tuberculin skin test) and treating LTB before or with initiation of IMID therapies. Available diagnostic tests have deficiencies in diagnostic sensitivity to detect LTB and even worse capability in predicting reactivation of TB. In addition to immunological tests, more stringent testing strategy utilizing one or many LTB equivalents may point towards subclinical TB. LTB equivalents include clinical (past history of TB, recent exposure to TB) and radiological criteria (use of chest roentgenogram, computed tomography, or, sometimes positron emission tomography - computed tomography). The present review summarizes the risk factors for TB reactivation in patients initiated on advanced therapies, geographically appropriate strategies for LTB testing, and treatment of LTB.

Development of chronic obstructive pulmonary disease after a tuberculosis episode in a large, population-based cohort from Eastern China

BACKGROUND

Although smoking is considered the primary cause of chronic obstructive pulmonary disease (COPD), there is a growing realization that there may be important secondary risk factors. Tuberculosis may lead to lung impairment; however, whether residual lung damage results in clinically significant, long-term outcomes, independent of smoking, has not been well studied. We aimed to investigate the association between tuberculosis and the subsequent development of COPD using a large, population-based cohort study.

METHODS

We conducted a longitudinal cohort study within the Chinese Electronic Health Records Research in Yinzhou study between 2009 and 2021. We followed participants free of COPD at the beginning of the study, and investigated whether previous or current tuberculosis was an important risk factor. Tuberculosis was recorded based on the Chinese National Disease Reporting system which includes all diagnosed cases at the city, provincial and national levels. We assessed the relationship between tuberculosis and COPD using multivariable survival models, adjusting for demographic and lifestyle characteristics, education level, comorbidities and use of medications.

RESULTS

Among 477 046 participants, 198 882 were eligible for inclusion in our analysis. In a multivariable model, pulmonary tuberculosis and all tuberculosis were associated with a 2.57-fold [95% confidence interval (CI), 2.31-2.87)] and 1.67-fold (95% CI, 1.48-1.90) increased COPD risk, respectively. Stronger associations of pulmonary tuberculosis and all tuberculosis with COPD were seen in participants who were elderly, or with lower body mass index or education level (Pinteraction<0.001). People with tuberculosis were at an increased risk of COPD if they were current smokers [adjusted hazard ratio (aHR), 1.40; 95% CI, 1.02-1.93] or non-smokers (aHR, 1.72; 95% CI, 1.50-1.98).

CONCLUSIONS

Persons who developed tuberculosis were at much greater risk of developing COPD, even accounting for smoking and other potential confounders.

Management of tuberculosis risk, screening and preventive therapy in patients with chronic autoimmune arthritis undergoing biotechnological and targeted immunosuppressive agents

Tuberculosis (TB) is the leading cause of death in the world from an infectious disease. Its etiologic agent, the Mycobacterium tuberculosis (Mtb), is a slow-growing bacterium that has coexisted in humans for thousands of years. According to the World Health Organization, 10.6 million new cases of TB and over 1 million deaths were reported in 2022. It is widely recognized that patients affected by chronic autoimmune arthritis such as rheumatoid arthritis (RA), psoriatic arthritis (PsA), and ankylosing spondylitis (AS) have an increased incidence rate of TB disease compared to the general population. As conceivable, the risk is associated with age ≥65 years and is higher in endemic regions, but immunosuppressive therapy plays a pivotal role. Several systematic reviews have analysed the impact of anti-TNF-α agents on the risk of TB in patients with chronic autoimmune arthritis, as well as for other biologic disease-modifying immunosuppressive anti-rheumatic drugs (bDMARDs) such as rituximab, abatacept, tocilizumab, ustekinumab, and secukinumab. However, the data are less robust compared to those available with TNF-α inhibitors. Conversely, data on anti-IL23 agents and JAK inhibitors (JAK-i), which have been more recently introduced for the treatment of RA and PsA/AS, are limited. TB screening and preventive therapy are recommended in Mtb-infected patients undergoing bDMARDs and targeted synthetic (ts)DMARDs. In this review, we evaluate the current evidence from randomized clinical trials, long-term extension studies, and real-life studies regarding the risk of TB in patients with RA, PsA, and AS treated with bDMARDs and tsDMARDs. According to the current evidence, TNF-α inhibitors carry the greatest risk of TB progression among bDMARDs and tsDMARDs, such as JAK inhibitors and anti-IL-6R agents. The management of TB screening and the updated preventive therapy are reported.

Tuberculosis Preventive Treatment in High TB-Burden Settings: A State-of-the-Art Review

Tuberculosis (TB) is the leading cause of death from a single infectious agent. The burden is highest in some low- and middle-income countries. One-quarter of the world's population is estimated to have been infected with TB, which is the seedbed for progressing from TB infection to the deadly and contagious disease itself. Although some individuals may clear their infections through innate and acquired immunity, many do not. People living with HIV, TB-exposed household contacts, other individuals recently infected, and immunosuppressed individuals are at especially high risk of progressing to TB disease. There have been major advances in recent years to support the programmatic management of TB infection. New tests of infection, including those that predict progression to TB disease, have become available. Numerous World Health Organization-recommended TB preventive treatment (TPT) regimens are available for all ages and for both drug-susceptible and drug-resistant TB infection. All regimens are generally safe, efficacious, and cost effective and have a low risk of generating resistance. TPT is recommended for pregnant women who are at risk for developing TB, but some regimens are associated with an increased likelihood of poor obstetric and fetal outcomes, and newer regimens have not yet been tested in pregnancy. New formulations of rifapentine-based TPT have been developed, and the cost has been radically reduced. Innovative models of delivery to support the scale up of TPT have been developed. Modeling suggests that scaling up TPT, especially regimens with optimal target product profile characteristics, can contribute substantially to ending the TB epidemic. The global uptake of TPT has increased substantially, especially for people living with HIV. Implementation gaps remain, particularly for children, pregnant women, and other household contacts. Further innovation is required to support the continued scale up of TPT and to contribute to ending the TB epidemic.

Mistakes to avoid in the management of abdominal tuberculosis

INTRODUCTION

The diagnosis and management of abdominal tuberculosis, i.e Gastrointestinal Tuberculosis (GITB) and tuberculous peritonitis (TBP) is challenging. Abdominal tuberculosis, presenting usually with abdominal pain, intestinal obstruction, and constitutional symptoms, is typically a paucibacillary condition. The diagnosis hinges on a correct interpretation of clinical, radiological, histological, biochemical, and microbiological findings as also appropriately assessing response to therapy.

AREAS COVERED

The authors review potential missteps that could occur in managing GITB and TBP sourced from published literature and clinical experience. These include avoiding excess use of tests with limited accuracy, understanding limitations of ascitic adenosine deaminase (ADA) and granulomas, avoiding empirical antitubercular therapy (ATT) where possible but also understanding that microbiological tests may not always be positive, and finally not to bank solely on subjective clinical responses but to use objective markers in assessing response to therapy. In addition, diagnosis of predisposing immunosuppressed states, attention to nutrition, appropriate management of sequelae with endoscopic dilatation/surgery, and early surgery when indicated are some of the additional issues discussed.

EXPERT OPINION

In future, a more secure diagnosis banking on the use of better microbiological tools, multiparameter-based models, artificial intelligence-based approaches, and use of advances in -omics-based approaches can improve diagnosis and avoid some missteps.

Screening for Asymptomatic Tuberculosis among Adults with Household Exposure to a Patient with Pulmonary Tuberculosis

Background

More than half of tuberculosis (TB) detected by community prevalence surveys is classified as asymptomatic. We evaluated yield of symptom and chest radiograph (CXR) screening of TB-exposed household contacts (HHC) in South Africa.

Methods

Adult volunteers (≥18 years) with household exposure to pulmonary TB patients were enrolled at three sites. Systematic screening of TB symptoms (any duration), CXR (any abnormality), and sputum microscopy, Xpert Ultra, and liquid culture were performed. Serum C-reactive protein (CRP) was measured by multiplex bead array. Prevalent TB was microbiologically-confirmed (Xpert Ultra or culture). Symptomatic and asymptomatic TB were defined as prevalent TB with and without reported symptoms, respectively.

Results

Between March 2021 - December 2022, 979 HHC were enrolled; 185 (18.9%) living with HIV and 187 (19.1%) with previous TB. Prevalent TB occurred in 51 (5.2%) and was asymptomatic in 42/51 (82.4%). Only 13/42 (31.0%) asymptomatic TB cases were smear-positive [8/13 (61.5%) graded scanty or 1+]. CRP did not discriminate healthy HHC from those with asymptomatic TB (AUC 0.60; 95%CI 0.47-0.73). An abnormal CXR was observed in 23/41 asymptomatic (sensitivity 56.1%, 95%CI 41.0-70.1%) versus 8/9 symptomatic (sensitivity 88.9%, 95%CI 56.5-98.0%) TB cases. Sensitivity of CXR in combination with symptom screening was 64.0% (32/50, 95%CI 50.1-75.9%) for all prevalent TB.

Conclusions

More than 80% of confirmed TB cases among HHC were asymptomatic. CXR screening missed more than 40% of these asymptomatic cases. Community prevalence surveys reliant on symptom- and CXR-based approaches may significantly underestimate the prevalence of asymptomatic TB in endemic countries.

Funding

Supported by RePORT South Africa through funding from the U.S. National Institutes of Health, CRDF Global, and the South African Medical Research Council.

RESEARCH IN CONTEXT

Evidence before this study: World Health Organisation (WHO) guidelines for systematic tuberculosis (TB) screening recommend symptom screening and chest radiography (CXR), based on a Cochrane meta-analysis reporting 70.6% sensitivity (any TB symptom) and 94.7% sensitivity (any CXR abnormality) for bacteriologically-confirmed pulmonary TB. National TB prevalence surveys rely on a positive symptom screen or abnormal CXR to trigger diagnostic sputum testing. This approach to community screening would, by definition, miss asymptomatic TB cases without CXR evidence of disease. We reviewed the reference list of the aforementioned meta-analysis for active case-finding studies of adolescents and adults aged 15 years and older in community and contact-tracing settings. We performed forward citation-tracking and searched reference lists, including studies published in English between Jan 1, 1980, and November 1, 2024. We excluded studies that included children <15 years; or that exclusively enrolled people with additional risk factors (HIV; diabetes; latent TB infection; prior TB). We found 28 studies that performed universal sputum testing for bacteriologically-confirmed pulmonary TB and reported 51.8% (95%CI 49.9-53.7%; I 2 = 89.2%) pooled sensitivity for symptom screening (any symptom; 24 studies, 2,969 TB cases) and 62.4% (95%CI 59.3-65.3%; I 2 = 88.3%) pooled sensitivity for CXR (any abnormality; 10 studies, 1,123 TB cases). Only four studies (145 TB cases) reported accuracy of symptom screening in parallel with chest radiography (pooled sensitivity 67.3%, 95%CI 57.3-75.9%; I 2 = 87.1%), but these studies did not disaggregate symptomatic and asymptomatic disease. Added value of this study: We performed systematic screening using universal sputum microbiological testing of 978 household contacts of pulmonary TB patients in three South African communities and compared symptom (any duration) and CXR (any abnormality) screening approaches against a microbiological reference standard. We detected confirmed pulmonary TB in 5.2% of household contacts, and 82.4% of these TB cases reported no TB symptoms. Asymptomatic TB in household contacts was pauci-bacillary and associated with low serum CRP levels that were indistinguishable from healthy controls, but distinct from symptomatic TB in a comparator group of clinic attendees. Sensitivity of CXR screening for asymptomatic TB was only 56.1%; sensitivity of combined symptom and CXR screening for all TB was marginally higher at 64.0%.Implications of all the available evidence: Our findings from household contacts suggest that symptom- and CXR-based approaches are inadequate for community TB screening in South Africa and do not meet the WHO Target Product Profile for a TB screening test (minimum 90% sensitivity; 70% specificity). National TB Prevalence Surveys that omit universal sputum microbiological testing may significantly underestimate the prevalence of asymptomatic TB in high-burden countries.

Efficacy of Xpert MTB/RIF assay in detecting Mycobacterium tuberculosis in samples with different results by smear and culture in a coastal city with high incidence of tuberculosis

BACKGROUND

Tuberculosis (TB) is a global problem that seriously jeopardizes human health. Among them, the diagnosis and treatment of smear- or culture-negative TB patients is a challenge. The Xpert MTB/RIF (Xpert) assay has been reported to be a novel molecular diagnostic tool for rapidly detecting TB. Still, there is limited data on this assay's performance in subgroups of TB patients. This study aimed to evaluate the diagnostic value of the Xpert method in patients with different smear and culture results and to assess its efficacy for rifampicin resistance (RR) detection.

METHODS

We retrospectively collected data from 1,721 patients with a clinical diagnosis of tuberculosis. Smear, Xpert, and traditional solid culture methods were used to detect TB infection and explore the detection rate of Xpert in the grouping of results from different smear and culture methods. Information on RR detected by the Xpert method and proportional method of drug sensitivity test (DST) was also recorded and kappa values, sensitivity, and specificity were calculated.

RESULTS

We observed that among the three methods, the Xpert method had the highest detection rate of 66.8%, followed by the culture method at 56.0% and the smear method had the lowest at 40.0%. The detection rate of Xpert was 98.3% (642/653) when both smear and culture were positive, 85.1% (296/348) when only one of the two methods, smear and culture, was positive, and 29.4% (212/720) when both smear and culture were negative. The Xpert method and DST showed a high agreement (κ = 0.92) for RR detection. The highest mutation rate was observed for probe E (64.7%), and the least number of probe C mutations occurred (1.5%).

CONCLUSION

The Xpert method has high detection efficiency. It has good diagnostic value in detecting MTB and RR, especially in cases where traditional culture and sputum smear results are negative, and significantly reduces the rate of missed diagnosis.

Incipient and subclinical tuberculosis: a narrative review

Mycobacterium tuberculosis has been known to infect humans for eons. It is an airborne infectious disease transmitted through droplet nuclei of 1 to 5 µm in diameter. Historically, tuberculosis (TB) was considered a distinct condition characterized by TB infection and active TB disease. However, recently, the concept of a dynamic spectrum of infection has emerged, wherein the pathogen is initially eradicated by the innate or adaptive immune system, either in conjunction with or independently of T cell priming. Other categories within this spectrum include TB infection, incipient TB, subclinical TB, and active TB disease. Various host- and pathogen-related factors influence these categories. Furthermore, subclinical TB can facilitate the spread of infection within the community. Due to its asymptomatic nature, there is a risk of delayed diagnosis, and some patients may remain undiagnosed. Individuals with subclinical TB may stay in this stage for an indeterminate period without progressing to active TB disease, and some may even experience regression. Early diagnosis and treatment of TB are essential to meet the 2035 targets outlined in the end-TB strategy. This strategy should also include incipient and subclinical TB. This review will focus on the definition, natural history, burden, trajectory, transmissibility, detection, and management of early-stage TB.

Immunopathology in human tuberculosis

Mycobacterium tuberculosis (M.tb) is a bacterial pathogen that has evolved in humans, and its interactions with the host are complex and best studied in humans. Myriad immune pathways are involved in infection control, granuloma formation, and progression to tuberculosis (TB) disease. Inflammatory cells, such as macrophages, neutrophils, conventional and unconventional T cells, B cells, NK cells, and innate lymphoid cells, interact via cytokines, cell-cell communication, and eicosanoid signaling to contain or eliminate infection but can alternatively mediate pathological changes required for pathogen transmission. Clinical manifestations include pulmonary and extrapulmonary TB, as well as post-TB lung disease. Risk factors for TB progression, in turn, largely relate to immune status and, apart from traditional chemotherapy, interventions primarily target immune mechanisms, highlighting the critical role of immunopathology in TB. Maintaining a balance between effector mechanisms to achieve protective immunity and avoid detrimental inflammation is central to the immunopathogenesis of TB. Many research gaps remain and deserve prioritization to improve our understanding of human TB immunopathogenesis.

Characterizing the immune response to Mycobacterium tuberculosis: a comprehensive narrative review and implications in disease relapse

Introduction

Tuberculosis remains the leading cause of death from infectious diseases among adults worldwide. To date, an overarching review of the immune response to Mtb in humans has not been fully elucidated, with innate immunity remaining poorly understood due to historic focus on adaptive immunity. Specifically, there is a major gap concerning the contribution of the immune system to overall bacterial clearance, particularly residual bacteria. This review aims to describe the time course of interactions between the host immune system and Mtb, from the start of the infection to the development of the adaptive response. Concordantly, we aim to crystallize the pathogenic effects and immunoevasive mechanisms of Mtb. The translational value of animal data is also discussed.

Methods

The literature search was conducted in the PubMed, ScienceDirect, and Google Scholar databases, which included reported research from 1990 until 2024. A total of 190 publications were selected and screened, of which 108 were used for abstraction and 86 were used for data extraction. Graphical summaries were created using the narrative information (i.e., recruitment, recognition, and response) to generate clear visual representations of the immune response at the cellular and molecular levels.

Results

The key cellular players included airway epithelial cells, alveolar epithelial cells, neutrophils, natural killer cells, macrophages, dendritic cells, T cells, and granulomatous lesions; the prominent molecular players included IFN-γ, TNF-α, and IL-10. The paper also sheds light on the immune response to residual bacteria and applications of the data.

Discussion

We provide a comprehensive characterization of the key immune players that are implicated in pulmonary tuberculosis, in line with the organs or compartments in which mycobacteria reside, offering a broad vignette of the immune response to Mtb and how it responds to residual bacteria. Ultimately, the data presented could provide immunological insights to help establish optimized criteria for identifying efficacious treatment regimens and durations for relapse prevention in the modeling and simulation space and wider fields.

Bayesian accuracy estimates for diagnostic tests to detect tuberculosis in captive sun bears (Helarctos malayanus) and Asiatic black bears (Ursus thibetanus) in Cambodia and Vietnam

Effective control of tuberculosis (TB) depends on early diagnosis of disease, yet available tests are unable to perfectly detect infected individuals. In novel hosts diagnostic testing methods for TB are extrapolated from other species, with unknown accuracy. The primary challenge to evaluating the accuracy of TB tests is the lack of a perfect reference test. Here we use a Bayesian latent class analysis approach to evaluate five tests available for ante-mortem detection of pulmonary TB in captive sun bears and Asiatic black bears in Southeast Asia. Using retrospective results from screening of 344 bears at three rescue centres, we estimate accuracy parameters for thoracic radiography, a serological assay (DPP VetTB), and three microbiological tests (microscopy, PCR (Xpert MTB/RIF, Xpert MTB/RIF Ultra), mycobacterial culture) performed on bronchoalveolar lavage samples. While confirming the high specificities (≥ 0.99) of the three microbiological tests, our model demonstrated their sub-optimal sensitivities (<0.7). Thoracic radiography was the only diagnostic method with sensitivity (0.95, 95% BCI: 0.76, 0.998) and specificity (0.95, 95% BCI: 0.91, 0.98) estimated above 0.9. We recommend caution when interpreting DPP VetTB results, with the increased sensitivity resulting from treatment of weakly visible reactions as positive accompanied by a drop in specificity, and we illustrate how the diagnostic value of weak DPP VetTB reactions is particularly reduced if disease prevalence and/or clinical suspicion is low. Conversely, the reduced utility of negative microbiological tests on bronchoalveolar lavage fluid samples when prevalence and/or clinical suspicion is high is demonstrated. Taken together our results suggest multiple tests should be applied and accompanied by consideration of the testing context, to minimise the consequences of misclassification of disease status of bears at risk of TB in sanctuary settings.

Effectiveness of Systematic Screening and Treatment of Tuberculosis in Prison in Thailand

The global incidence of tuberculosis (TB) in prison is 5 to 70 times greater than that in the general population. The systematic screening and treatment of TB in prison benefit TB control and treatment outcomes. However, no study has supported this in Thailand. Here, we evaluated the effectiveness of long-term, continuous, systematic screening for TB control. We conducted a retrospective study in Suratthani Central Prison, Thailand, using annual TB screening from 2016 to 2020. A positive TB screening was defined as having any TB symptoms or chest radiography abnormality. We collected sputum smear and Xpert® Mycobacterium tuberculosis/rifampicin (MTB/RIF) results from those inmates with positive screening results. Bacteriologically confirmed TB was defined as a positive sputum smear or M. tuberculosis detected by Xpert assay. Inmates with clinically diagnosed TB were also eligible for this study. Those inmates diagnosed with active TB were sent to an isolation zone in prison and received anti-TB medicine using directly observed therapy and were monitored by pulmonologists during the treatment course via telemedicine. Of 18,965 TB screening events, 175 patients were diagnosed with TB. The 5-year prevalence was 922 per 100,000 inmates. The relative reduction in TB prevalence was 60.5% from 2016 to 2020. Overall, 94.3% of TB patients were successfully treated (sum of patients cured and treatment completed). Three TB patients died during the 5-year study period. All occurred in 2016. The systematic screening and treatment of TB in inmates effectively reduced the prevalence and mortality in Suratthani Central Prison. The success rate of treatment in this prison has been consistently high.

Immune correlates of protection as a game changer in tuberculosis vaccine development

The absence of validated correlates of protection (CoPs) hampers the rational design and clinical development of new tuberculosis vaccines. In this review, we provide an overview of the potential CoPs in tuberculosis vaccine research. Major hindrances and potential opportunities are then discussed. Based on recent progress, it is reasonable to anticipate that success in the ongoing efforts to identify CoPs would be a game-changer in tuberculosis vaccine development.

Implications of subclinical tuberculosis for vaccine trial design and global effect

Tuberculosis is a leading cause of death from an infectious agent globally. Infectious subclinical tuberculosis accounts for almost half of all tuberculosis cases in national tuberculosis prevalence surveys, and possibly contributes to transmission and might be associated with morbidity. Modelling studies suggest that new tuberculosis vaccines could have substantial health and economic effects, partly based on the assumptions made regarding subclinical tuberculosis. Evaluating the efficacy of prevention of disease tuberculosis vaccines intended for preventing both clinical and subclinical tuberculosis is a priority. Incorporation of subclinical tuberculosis as a composite endpoint in tuberculosis vaccine trials can help to reduce the sample size and duration of follow-up and to evaluate the efficacy of tuberculosis vaccines in preventing clinical and subclinical tuberculosis. Several design options with various benefits, limitations, and ethical considerations are possible in this regard, which would allow for the generation of the evidence needed to estimate the positive global effects of tuberculosis vaccine trials, in addition to informing policy and vaccination strategies.

Molecular and microbiological methods for the identification of nonreplicating Mycobacterium tuberculosis

Chronic tuberculosis (TB) disease, which requires months-long chemotherapy with multiple antibiotics, is defined by diverse pathological manifestations and bacterial phenotypes. Targeting drug-tolerant bacteria in the host is critical to achieving a faster and durable cure for TB. In order to facilitate this field of research, we need to consider the physiology of persistent MTB during infection, which is often associated with the nonreplicating (NR) state. However, the traditional approach to quantifying bacterial burden through colony enumeration alone only informs on the abundance of live bacilli at the time of sampling, and provides an incomplete picture of the replicative state of the pathogen and the extent to which bacterial replication is balanced by ongoing cell death. Modern approaches to profiling bacterial replication status provide a better understanding of inter- and intra-population dynamics under different culture conditions and in distinct host microenvironments. While some methods use molecular markers of DNA replication and cell division, other approaches take advantage of advances in the field of microfluidics and live-cell microscopy. Considerable effort has been made over the past few decades to develop preclinical in vivo models of TB infection and some are recognized for more closely recapitulating clinical disease pathology than others. Unique lesion compartments presenting different environmental conditions produce significant heterogeneity between Mycobacterium tuberculosis populations within the host. While cellular lesion compartments appear to be more permissive of ongoing bacterial replication, caseous foci are associated with the maintenance of M. tuberculosis in a state of static equilibrium. The accurate identification of nonreplicators and where they hide within the host have significant implications for the way novel chemotherapeutic agents and regimens are designed for persistent infections.

Critical assessment of infants born to mothers with drug resistant tuberculosis

Background

There have been no detailed descriptions of infants born to mothers treated for drug resistant TB in pregnancy. Critical case history assessment is important to identify risks and guide clinical practice.

Methods

In a cohort of pregnant women with multidrug or rifampicin resistant (MDR/RR)-TB enrolled between 1 January 2013 and 31 December 2022, we followed mother-infant pairs until the infant was 12 months old. We performed critical case history assessments to explore potential mechanisms of Mycobacterium tuberculosis transmission to the infant, and to describe the clinical presentation and disease trajectories observed in infants diagnosed with TB.

Findings

Among 101 mother-infant pairs, 23 (23%) included infants diagnosed with TB disease; 16 were clinically diagnosed and seven had microbiological confirmation (five MDR/RR-TB, two drug-susceptible TB). A positive maternal sputum culture at the time of delivery was significantly associated with infant TB risk (p = 0.023). Of the 12 infants diagnosed with TB in the first three months of life, seven (58%) of the mothers were culture positive at delivery; of whom four reported poor TB treatment adherence. However, health system failures, including failing to diagnose and treat maternal MDR/RR-TB, inadequate screening of newborns at birth, not providing appropriate TB preventive therapy (TPT), and M. tuberculosis transmission from non-maternal sources also contributed to TB development in infants.

Interpretation

Infants born to mothers with MDR/RR-TB are at greatest risk if maternal adherence to MDR/RR-TB treatment or antiretroviral therapy (ART) is sub-optimal. In a high TB incidence setting, infants are also at risk of non-maternal household and community transmission. Ensuring maternal TB diagnosis and appropriate treatment, together with adequate TB screening and prevention in all babies born to mothers or households with TB will minimise the risk of infant TB disease development.

Funding

South African Medical Research Council.

Persistent Mycobacterium tuberculosis bioaerosol release in a tuberculosis-endemic setting

Pioneering studies linking symptomatic disease and cough-mediated Mycobacterium tuberculosis (Mtb) release established the infectious origin of tuberculosis (TB), simultaneously informing the notion that pathology is a prerequisite for Mtb transmission. Our recent work has challenged this assumption: by sampling TB clinic attendees, we detected equivalent release of Mtb-containing bioaerosols by confirmed TB patients and individuals not receiving a TB diagnosis and observed time-dependent reduction in Mtb bioaerosol positivity during 6-month follow-up of both cohorts, irrespective of anti-TB chemotherapy. Now, we report widespread Mtb release in our TB-endemic setting: of 89 randomly recruited community members, 79.8% (71/89) produced Mtb-containing bioaerosols independently of QuantiFERON status, a standard test for Mtb exposure. Moreover, during 2-month longitudinal sampling, only 2% (1/50) were serially Mtb bioaerosol negative. These results necessitate a reframing of the prevailing paradigm of Mtb transmission and TB etiology, perhaps explaining the historical inability to elucidate Mtb transmission networks in TB-endemic regions.

Community-Wide Active Case Finding for Tuberculosis: Time to Use the Evidence We Have

Tuberculosis, caused by the Mycobacterium tuberculosis (Mtb) bacteria, is one of the world's deadliest infectious diseases. Despite being the world's oldest pandemic, tuberculosis is very much a challenge of the modern era. In high-incidence settings, all people are at risk, irrespective of whether they have common vulnerabilities to the disease warranting the current WHO recommendations for community-wide tuberculosis active case finding in these settings. Despite good evidence of effectiveness in reducing tuberculosis transmission, uptake of this strategy has been lacking in the communities that would derive greatest benefit. We consider the various complexities in eliminating tuberculosis from the first principles of the disease, including diagnostic and other challenges that must be navigated under an elimination agenda. We make the case that community-wide tuberculosis active case finding is the best strategy currently available to drive elimination forward in high-incidence settings and that no time should be lost in its implementation. Recognizing that high-incidence communities vary in their epidemiology and spatiosocial characteristics, tuberculosis research and funding must now shift towards radically supporting local implementation and operational research in communities. This "preparing of the ground" for scaling up to community-wide intervention centers the local knowledge and local experience of community epidemiology to optimize implementation practices and accelerate reductions in community-level tuberculosis transmission.

Mycobacterium tuberculosis cough aerosol culture status associates with host characteristics and inflammatory profiles

Interrupting transmission events is critical to tuberculosis control. Cough-generated aerosol cultures predict tuberculosis transmission better than microbiological or clinical markers. We hypothesize that highly infectious individuals with pulmonary tuberculosis (positive for cough aerosol cultures) have elevated inflammatory markers and unique transcriptional profiles compared to less infectious individuals. We performed a prospective, longitudinal study using cough aerosol sampling system. We enrolled 142 participants with treatment-naïve pulmonary tuberculosis in Kenya and assessed the association of clinical, microbiologic, and immunologic characteristics with Mycobacterium tuberculosis aerosolization and transmission in 129 household members. Contacts of the forty-three aerosol culture-positive participants (30%) are more likely to have a positive interferon-gamma release assay (85% vs 53%, P = 0.006) and higher median IFNγ level (P < 0.001, 4.28 IU/ml (1.77-5.91) vs. 0.71 (0.01-3.56)) compared to aerosol culture-negative individuals. We find that higher bacillary burden, younger age, larger mean upper arm circumference, and host inflammatory profiles, including elevated serum C-reactive protein and lower plasma TNF levels, associate with positive cough aerosol cultures. Notably, we find pre-treatment whole blood transcriptional profiles associate with aerosol culture status, independent of bacillary load. These findings suggest that tuberculosis infectiousness is associated with epidemiologic characteristics and inflammatory signatures and that these features may identify highly infectious persons.

Altered hepatic metabolic landscape and insulin sensitivity in response to pulmonary tuberculosis

Chronic inflammation triggers development of metabolic disease, and pulmonary tuberculosis (TB) generates chronic systemic inflammation. Whether TB induced-inflammation impacts metabolic organs and leads to metabolic disorder is ill defined. The liver is the master regulator of metabolism and to determine the impact of pulmonary TB on this organ we undertook an unbiased mRNA and protein analyses of the liver in mice with TB and reanalysed published data on human disease. Pulmonary TB led to upregulation of genes in the liver related to immune signalling and downregulation of genes encoding metabolic processes. In liver, IFN signalling pathway genes were upregulated and this was reflected in increased biochemical evidence of IFN signalling, including nuclear location of phosphorylated Stat-1 in hepatocytes. The liver also exhibited reduced expression of genes encoding the gluconeogenesis rate-limiting enzymes Pck1 and G6pc. Phosphorylation of CREB, a transcription factor controlling gluconeogenesis was drastically reduced in the livers of mice with pulmonary TB as was phosphorylation of other glucose metabolism-related kinases, including GSK3a, AMPK, and p42. In support of the upregulated IFN signalling being linked to the downregulated metabolic functions in the liver, we found suppression of gluconeogenic gene expression and reduced CREB phosphorylation in hepatocyte cell lines treated with interferons. The impact of reduced gluconeogenic gene expression in the liver was seen when infected mice were less able to convert pyruvate, a gluconeogenesis substrate, to the same extent as uninfected mice. Infected mice also showed evidence of reduced systemic and hepatic insulin sensitivity. Similarly, in humans with TB, we found that changes in a metabolite-based signature of insulin resistance correlates temporally with successful treatment of active TB and with progression to active TB following exposure. These data support the hypothesis that TB drives interferon-mediated alteration of hepatic metabolism resulting in reduced gluconeogenesis and drives systemic reduction of insulin sensitivity.

Persistent Mycobacterium tuberculosis bioaerosol release in a tuberculosis-endemic setting

Pioneering studies linking symptomatic disease and cough-mediated release of Mycobacterium tuberculosis (Mtb) established the infectious origin of tuberculosis (TB), simultaneously informing the pervasive notion that pathology is a prerequisite for Mtb transmission. Our prior work has challenged this assumption: by sampling TB clinic attendees, we detected equivalent release of Mtb-containing bioaerosols by confirmed TB patients and individuals not receiving a TB diagnosis, and we demonstrated a time-dependent reduction in Mtb bioaerosol positivity during six-months' follow-up, irrespective of anti-TB chemotherapy. Now, by extending bioaerosol sampling to a randomly selected community cohort, we show that Mtb release is common in a TB-endemic setting: of 89 participants, 79.8% (71/89) produced Mtb bioaerosols independently of QuantiFERON-TB Gold status, a standard test for Mtb infection; moreover, during two-months' longitudinal sampling, only 2% (1/50) were serially Mtb bioaerosol negative. These results necessitate a reframing of the prevailing paradigm of Mtb transmission and infection, and may explain the current inability to elucidate Mtb transmission networks in TB-endemic regions.

Test and treat approach for tuberculosis infection amongst household contacts of drug-susceptible pulmonary tuberculosis, Mumbai, India

Background

Mumbai is one of the most densely populated areas in the world and is a major contributor to the tuberculosis (TB) epidemic in India. A test and treat approach for TB infection (TBI) amongst household contacts (HHC) is part of the national policy for TB preventive treatment (TPT). However, in practice, the use of interferon-gamma release assay (IGRA) tests for infection are limited, and prevalence of TBI in Mumbai is not known.

Methods

We conducted a cross-sectional study among HHCs exposed to persons with microbiologically-confirmed, drug-susceptible pulmonary TB that were notified for antituberculosis treatment in Mumbai, India during September-December, 2021. Community-based field workers made home visits and offered IGRA (QuantiFERON-TB® Gold In-Tube Plus) tests to HHC aged 5 years and older. After ruling out active TB disease, HHC with IGRA-positive test results were referred for TPT. All HHC were monitored for at least 24 months for progression to active TB disease.

Results

Among 502 HHCs tested, 273 (54%) had IGRA-positive results. A total of 254 (93%) were classified as TBI and were eligible for TPT, of which 215 (85%) initiated TPT, and 194 (90%) completed TPT successfully. There was substantial variation in rates of TBI per household. In 32% of households, all HHC (100%) were IGRA positive and in 64% of households >50% of HHC were infected. In all, 22 HHCs (4%; 22/558) were diagnosed with TB disease; of these, five HHC were diagnosed during follow up, of which three were IGRA positive and had no evidence of disease at initial screening but chose not to initiate TPT.

Conclusion

A test and treat strategy for HHC resulted in the detection of a substantial proportion of TBI and secondary TB cases. Home-based IGRA testing led to high participation rates, clinical evaluations, TPT initiation, and early diagnoses of additional secondary cases. A community-focused, test and treat approach was feasible in this population and could be considered for broader implementation.