Implementation of tuberculosis preventive therapy with INH-Rifapentine (3HP) for latent tuberculosis infection management in household tuberculosis contacts in India: A prospective study

OBJECTIVE

The primary objective of this study was to ascertain the acceptance, initiation, implementation and treatment completion rates of tuberculosis (TB) preventive therapy (TPT) using 3HP (INH-Rifapentine) among household contacts of microbiologically confirmed drug sensitive TB cases on anti-tubercular treatment under programmatic real-world settings. The secondary objectives were to estimate the prevalence and predictors of latent TB infection (LTBI) in household contacts of the index TB cases. We also ascertained the safety profile of the 3HP TPT regimen in the household contacts.

METHODS

This prospective observational study was conducted at 10 TB chest clinics in Delhi, India during 2022-2023. Household contacts aged 14 and older who tested positive for TB infection on a Tuberculin Skin test were initiated on the 3HP regimen. Logistic regression was performed by including statistically significant independent variables in multiple prediction models. p < 0.05 was considered statistically significant. STATA, version 15.1, was used to compute all analyses.

RESULTS

A total of 1067 (84.68%) eligible contacts of microbiologically confirmed, drug sensitive TB cases underwent screening with tuberculin skin test (TST), 614 (95.6%) LTBI positive contacts accepted the initiation of TPT, and 564 (91.8%) of those initiated on TPT completed the treatment. The major reason for refusal of screening was the lack of perception of risk of TB disease due to asymptomatic status. The prevalence of LTBI positivity through TST was 61.5% (95% CI, 58.5%, 64.4%). Adverse events were reported by 195 (31.8%) contacts initiated on 3HP of which 20 participants discontinued TPT. None of the sociodemographic factors showed a significant association with LTBI positivity (except age) or TPT completion rates.

CONCLUSION

LTBI management with 3HP is feasible among adolescent and adult household contacts in India with high rates of adherence from initiation until treatment completion. The maximum attrition of participants occurred at the time of screening for LTBI using TST.

Pediatric Drug-Resistant Tuberculosis: The Current and Future Prospects for Management and Prevention

In the continued battle against one of the oldest enemies known to mankind, Mycobacterium tuberculosis (MTB), the emergence of drug resistance to antituberculosis drugs among children poses multiple challenges for early detection and treatment. Molecular diagnostics and newer drugs like bedaquiline and delamanid have strengthened the armamentarium and helped design convenient, safe, and child-friendly therapeutic regimens against drug-resistant tuberculosis (TB). Preventive strategies like treatment of TB infection among children living in close contact with patients with drug-resistant TB and effective vaccines against TB are currently in the investigative stages of development and implementation. In addition to the implementation of recent novel diagnostics and treatment modalities, effective psychosocial and nutritional support, as well as dedicated monitoring for compliance and adverse effects, are crucial determinants for successful treatment outcomes in these children.

Comparison of the Standard E TB-Feron ELISA and QuantiFERON-TB Gold PLUS assays: the advantageous use of whole recombinant protein antigens for latent tuberculosis diagnosis

The laboratory diagnosis of latent tuberculosis is often performed using interferon-gamma release assays. Here, we compared two enzyme-linked immunosorbent assay-based interferon-gamma release assays, namely, the newly developed Standard E TB-Feron enzyme-linked immunosorbent assay (STFE) and the QuantiFERON-TB Gold PLUS assay (QFT-GP), using samples from 155 participants. The STFE is based on using whole EAST6 and CFP10 recombinant antigens for latent tuberculosis diagnosis. The participants were classified into four groups and screened using both assays per the manufacturers' instructions. Thereafter, two statistical analyses were conducted to compare the obtained results. First, the STFE results were compared with the QTF-GP results (used as the gold standard) to calculate the total concordance, sensitivity, and specificity of STFE. Second, positivity and negativity concordances were calculated to differentiate healthy participants from participants with tuberculosis. The STFE showed 97% and 94% sensitivity and specificity, respectively. Furthermore, its positivity and negativity concordances were 91% and 98%, respectively. These results indicate the coordinated clinical performance of STFE in detecting latent tuberculosis and its improved performance in targeting tuberculosis-infected participants. Based on the comparison of the latent tuberculosis diagnostic abilities of STFE and QFT-GP, we establish the suitability and superior performance of STFE as a diagnostic tool.

Immune interaction between SARS-CoV-2 and Mycobacterium tuberculosis

SARS-CoV-2 and Mycobacterium tuberculosis (Mtb) are major infectious causes of death, with meta-analyses and population-based studies finding increased mortality in co-infected patients simultaneously diagnosed with COVID-19 and tuberculosis (TB). There is a need to understand the immune interaction between SARS-CoV-2 and Mtb which impacts poor outcomes for those co-infected. We performed a PubMed and preprint search using keywords [SARS-CoV-2] AND [tuberculosis] AND [Immune response], including publications after January 2020, excluding reviews or opinions. Abstracts were evaluated by authors for inclusion of data specifically investigating the innate and/or acquired immune responses to SARS-CoV-2 and Mtb in humans and animal models, immunopathological responses in co-infection and both trials and investigations of potential protection against SARS-CoV-2 by Bacille Calmette Guérin (BCG). Of the 248 articles identified, 39 were included. Incidence of co-infection is discussed, considering in areas with a high burden of TB, where reported co-infection is likely underestimated. We evaluated evidence of the clinical association between COVID-19 and TB, discuss differences and similarities in immune responses in humans and in murine studies, and the implications of co-infection. SARS-CoV-2 and Mtb have both been shown to modulate immune responses, particularly of monocytes, macrophages, neutrophils, and T cells. Co-infection may result in impaired immunity to SARS-CoV-2, with an exacerbated inflammatory response, while T cell responses to Mtb may be modulated by SARS-CoV-2. Furthermore, there has been no proven potential COVID-19 clinical benefit of BCG despite numerous large-scale clinical trials.

Tuberculosis: Pathogenesis, Current Treatment Regimens and New Drug Targets

Mycobacterium tuberculosis (M. tb), the causative agent of TB, is a recalcitrant pathogen that is rife around the world, latently infecting approximately a quarter of the worldwide population. The asymptomatic status of the dormant bacteria escalates to the transmissible, active form when the host's immune system becomes debilitated. The current front-line treatment regimen for drug-sensitive (DS) M. tb strains is a 6-month protocol involving four different drugs that requires stringent adherence to avoid relapse and resistance. Poverty, difficulty to access proper treatment, and lack of patient compliance contributed to the emergence of more sinister drug-resistant (DR) strains, which demand a longer duration of treatment with more toxic and more expensive drugs compared to the first-line regimen. Only three new drugs, bedaquiline (BDQ) and the two nitroimidazole derivatives delamanid (DLM) and pretomanid (PMD) were approved in the last decade for treatment of TB-the first anti-TB drugs with novel mode of actions to be introduced to the market in more than 50 years-reflecting the attrition rates in the development and approval of new anti-TB drugs. Herein, we will discuss the M. tb pathogenesis, current treatment protocols and challenges to the TB control efforts. This review also aims to highlight several small molecules that have recently been identified as promising preclinical and clinical anti-TB drug candidates that inhibit new protein targets in M. tb.

System-wide identification of myeloid markers of TB disease and HIV-induced reactivation in the macaque model of Mtb infection and Mtb/SIV co-infection

Mycobacterium tuberculosis (Mtb) has developed specialized mechanisms to parasitize its host cell, the macrophage. These mechanisms allow it to overcome killing by oxidative burst and persist in the wake of an inflammatory response. Mtb infection in the majority of those exposed is controlled in an asymptomatic form referred to as latent tuberculosis infection (LTBI). HIV is a well-known catalyst of reactivation of LTBI to active TB infection (ATB). Through the use of nonhuman primates (NHPs) co-infected with Mtb and Simian Immunodeficiency Virus (Mtb/SIV), we are able to simulate human progression of TB/AIDS comorbidity. The advantage of NHP models is that they recapitulate the breadth of human TB outcomes, including immune control of infection, and loss of this control due to SIV co-infection. Identifying correlates of immune control of infection is important for both vaccine and therapeutics development. Using macaques infected with Mtb or Mtb/SIV and with different clinical outcomes we attempted to identify signatures between those that progress to active infection after SIV challenge (reactivators) and those that control the infection (non-reactivators). We particularly focused on pathways relevant to myeloid origin cells such as macrophages, as these innate immunocytes have an important contribution to the initial control or the lack thereof, following Mtb infection. Using bacterial burden, C-reactive protein (CRP), and other clinical indicators of disease severity as a guide, we were able to establish gene signatures of host disease state and progression. In addition to gene signatures, clustering algorithms were used to differentiate between host disease states and identify relationships between genes. This allowed us to identify clusters of genes which exhibited differential expression profiles between the three groups of macaques: ATB, LTBI and Mtb/SIV. The gene signatures were associated with pathways relevant to apoptosis, ATP production, phagocytosis, cell migration, and Type I interferon (IFN), which are related to macrophage function. Our results suggest novel macrophage functions that may play roles in the control of Mtb infection with and without co-infection with SIV. These results particularly point towards an interplay between Type I IFN signaling and IFN-γ signaling, and the resulting impact on lung macrophages as an important determinant of progression to TB.

Elevated IP-10 at the Protein and Gene Level Associates With Pulmonary TB

There is an urgent need for accurate and sensitive diagnostic tools that can overcome the current challenge to distinguish individuals with latent tuberculosis infection (LTBI) from individuals with active tuberculosis (TB). Recent literature has suggested that a group of cytokines may serve as biomarkers of TB disease progression. Using a multiplex ELISA, we quantified 27 circulatory markers present within the unstimulated plasma of individuals in Durban, South Africa who were healthy (n=20), LTBI (n=13), or had active TB (n=30). RT-qPCR was performed to measure gene expression of the cytokines of interest, using RNA isolated from healthy (n=20), LTBI (n=20), or active TB (n=30). We found that at the protein level, IL-1RA, IL-6, and IP-10 were significantly more abundant in participants with active TB (p< 0.05) compared to those with LTBI individuals. IP-10 also showed the strongest association with active TB compared to healthy and LTBI at mRNA level. Our data shows that these proteins may serve as biomarkers of TB at both the protein and gene level.

TB and COVID-19: An Exploration of the Characteristics and Resulting Complications of Co-infection

Tuberculosis (TB) and Coronavirus Disease-19 (COVID-19) infection are two respiratory diseases that are of particular concern epidemiologically. Tuberculosis is one of the oldest diseases recorded in the history of mankind dating back thousands of years. It is estimated that approximately one quarter of the world’s population is infected with latent Mycobacterium tuberculosis (LTBI). This contrasts with COVID-19, which emerged in late 2019. Data continues to accumulate and become available on this pathogen, but the long-term side effect of fibrotic damage in COVID-19 patients evokes parallels between this novel coronavirus and its ancient bacterial affiliate. This similarity as well as several others may incite inquiries on whether coinfection of individuals with latent TB and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) lead to excessive fibrosis in the lungs and thus the emergence of an active TB infection. While it is well understood how TB leads to structural and immunological lung complications including granuloma formation, fibrosis, and T cell exhaustion, less is known about the disease course when coinfection with SARS-CoV-2 is present. Past and present research demonstrate that IL-10, TNF-α, IFN class I-III, TGF-β, IL-35, and Regulatory T cells (T-regs) are all important contributors of the characteristics of host response to mycobacterium tuberculosis. It has also been noted with current research that IL-10, TNF-α, IFN class I, II, and III, TGF-β, ACE-2, and T-regs are also important contributors to the host response to the SARS-CoV-2 virus in different ways than they are to the TB pathogen. Both pathogens may lead to an unbalanced inflammatory immune response, and together a shared dysregulation of immune response suggests an increased risk of severity and progression of both diseases. We have reviewed 72 different manuscripts between the years 1992 and 2021. The manuscripts pertaining to the SARS-COV-2 virus specifically are from the years 2020 and 2021. Our literature review aims to explore the biomolecular effects of these contributors to pathogenicity of both diseases along with current publications on TB/COVID-19 coinfection, focusing on the pathogenicity of SARS-CoV-2 infection with both latent and active TB, as well as the challenges in treating TB during the COVID-19 pandemic. The compiled material will then aid the latticework foundation of knowledge for future research leading to a hopeful improved system of therapeutic strategies for coinfection.

Myeloid-Derived Suppressor Cells Mediate T Cell Dysfunction in Nonhuman Primate TB Granulomas

Myeloid-derived suppressor cells (MDSCs) represent an innate immune cell population comprised of immature myeloid cells and myeloid progenitors with very potent immunosuppressive potential. MDSCs are reported to be abundant in the lungs of active tuberculosis (TB) patients. We sought to perform an in-depth study of MDSCs during latent TB infection (LTBI) and active TB (ATB) using the nonhuman primate (NHP) model of pulmonary TB. We found a higher proportion of granulocytic, polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) in the lungs of ATB animals compared to those with LTBI or naive control animals. Active disease in the lung, but not LTBI, was furthermore associated with higher proliferation, expansion, and immunosuppressive capabilities of PMN-MDSCs, as shown by enhanced expression of Ki67, indoleamine 2,3-dioxygenase (IDO1), interleukin-10 (IL-10), matrix metallopeptidase 9 (MMP-9), inducible nitric oxide synthase (iNOS), and programmed death-ligand 1 (PD-L1). These immunosuppressive PMN-MDSCs specifically localized to the lymphocytic cuff at the periphery of the granulomas in animals with ATB. Conversely, these cells were scarcely distributed in interstitial lung tissue and the inner core of granulomas. This spatial regulation suggests an important immunomodulatory role of PMN-MDSCs by restricting T cell access to the TB granuloma core and can potentially explain dysfunctional anti-TB responses in active granuloma. Our results raise the possibility that the presence of MDSCs can serve as a biomarker for ATB, while their disappearance can indicate successful therapy. Furthermore, MDSCs may serve as a potential target cell for adjunctive TB therapy.

Comparative Efficacy of Rifapentine Alone and in Combination with Isoniazid for Latent Tuberculosis Infection: a Translational Pharmacokinetic-Pharmacodynamic Modeling Study

Rifapentine has facilitated treatment shortening for latent tuberculosis infection (LTBI) in combination with isoniazid once weekly for 3 months (3HP) or daily for 1 month (1HP). Our objective was to determine the optimal rifapentine dose for a 6-week monotherapy regimen (6wP) and predict clinical efficacy. Rifapentine and isoniazid pharmacokinetics were simulated in mice and humans. Mouse lung CFU data were used to characterize exposure-response relationships of 1HP, 3HP, and 6wP and translated to predict clinical efficacy. A 600-mg daily dose for 6wP delivered greater cumulative rifapentine exposure than 1HP or 3HP. The maximum regimen effect (E_max) was 0.24 day^-1. The regimen potencies, measured as the concentration at 50% of E_max (EC₅₀), were estimated to be 2.12 mg/liter for 3HP, 3.72 mg/liter for 1HP, and 4.71 mg/liter for 6wP, suggesting that isoniazid contributes little to 1HP efficacy. Clinical translation predicted that 6wP reduces bacterial loads at a higher rate than 3HP and to a greater extent than 3HP and 1HP. 6wP (600 mg daily) is predicted to result in equal or better efficacy than 1HP and 3HP for LTBI treatment without the potential added toxicity of isoniazid. Results from ongoing and future clinical studies will be required to support these findings.

Genital tuberculosis screening at an academic fertility center in the United States

BACKGROUND

Infertility is a common presentation of female genital tuberculosis in endemic areas. Female genital tuberculosis-related maternal and neonatal complications have increased in recent years after assisted reproductive technology treatments. Despite rising emigration rates to the United States, guidelines to identify those with latent tuberculosis or female genital tuberculosis in fertility centers do not exist.

OBJECTIVE

This study aimed to characterize the prevalence of female genital tuberculosis in infertile patients at our academic fertility center.

STUDY DESIGN

This is a prospective cohort study. All patients presenting for infertility evaluation between January 2014 and January 2017 were assessed for risk factors for latent tuberculosis. Patients at risk for latent tuberculosis underwent screening using QuantiFERON-TB Gold serum assay. QuantiFERON-TB Gold-positive patients underwent further testing for female genital tuberculosis consisting of endometrial biopsy with histopathologic examination by a clinical pathologist, polymerase chain reaction for tuberculosis, and culture for acid-fast Mycobacterium tuberculosis.

RESULTS

Twenty-five of 323 infertility patients (7.7%) screened for latent tuberculosis had positive QuantiFERON-TB Gold results. A greater number of patients with a positive test result for QuantiFERON-TB Gold were foreign born than those with a negative test result for QuantiFERON-TB Gold (92% vs 29%; P<.001). Of note, the QuantiFERON-TB Gold-positive population had a higher incidence of both recurrent pregnancy loss (28% vs 7%; P=.003) and Asherman syndrome (8% vs 0.3%; P<.001). Among those with a positive test result for QuantiFERON-TB Gold, chest x-ray was abnormal in only 2 patients (8.0%). Endometrium evaluation revealed abnormalities in 2 patients (8.0%), in whom chest x-ray was normal, with 1 showing evidence of female genital tuberculosis. This was indicated by histology consistent with chronic granulomatous endometritis and positive endometrial testing for tuberculosis by polymerase chain reaction, acid-fast bacilli smear, and culture for Mycobacterium tuberculosis.

CONCLUSION

Although the prevalence of female genital tuberculosis in infertile women in the United States seems to be low, this study indicates that it can be underdiagnosed without utilization of multiple diagnostic modalities including endometrial sampling. Given the potential for serious maternal and neonatal morbidity in affected patients utilizing assisted reproductive technology, we propose that all at-risk women seeking infertility care in the United States be screened for latent tuberculosis. In patients who screen positive, endometrial biopsy should be obtained for evaluation by histology, polymerase chain reaction, and culture for Mycobacterium tuberculosis to rule out female genital tuberculosis before infertility treatments are initiated.

High prevalence of latent tuberculosis in hematopoietic stem cell transplant recipients: A First Report

TB is an increasing health problem, and patients undergoing HSCT are more prone to develop tuberculosis. The aim of our study was to evaluate prevalence of latent tuberculosis in HSCT recipients. In this study, 84 patients (2 months to 18 years) who were candidates for HSCT at the referral hospital of Tehran Children's Medical Center were enrolled. The TST and the QFT-GIT test were performed in all 84 patients, simultaneously. LTBI was considered when one of the tests was positive. Overall, the prevalence of LTBI in HSCT recipients in our study was 12% (10 cases). TST induration ≥5 mm was seen in only three patients (3.5%). Eight patients (9.5%) had a positive result for IGRA test, and 11 of them (13%) had indeterminate QFT-GIT result. The agreement between the TST results (induration size ≥5 mm) and the QFT-GIT results was poor (kappa = 0.14). In conclusion, there was a high rate of discordance between TST and IGRA results with many more positive QFT-GIT tests. However, more studies are needed in this population to determine whether this discordance reflects true infection.

Age-specific prevalence of TB infection among household contacts of pulmonary TB: Is it time for TB preventive therapy?

BACKGROUND

Household contacts (HHCs) of TB patients are at high risk of developing evidence of latent TB infection (LTBI) and active disease from the index patient. We estimated the age-specific prevalence of LTBI and the force of infection (FI), as a measure of recent transmission, among HHCs of active TB patients.

METHODS

A cross-sectional analysis of HHCs of pulmonary TB patients enrolled in a prospective study, 'CTRIUMPh', was conducted at two sites in India. LTBI was defined as either a positive tuberculin skin test (induration ≥5 mm) or QuantiFERON-Gold in tube test (value ≥0.35 IU/ml) and was stratified by age. FI, which is a measure of recent transmission of infection and calculated using changes in age-specific prevalence rates at specific ages, was calculated. Factors associated with LTBI were determined by logistic regression models.

RESULTS

Of 1020 HHCs of 441 adult pulmonary TB cases, there were 566 (55%) females and 289 (28%) children aged ≤15 y. While screening for the study 3% of HHC were diagnosed with active TB. LTBI prevalence among HHCs of pulmonary TB was 47% at <6 y, 53% between 6-14 y and 78% between 15-45 y. FI increased significantly with age, from 0.4 to 1.15 in the HHCs cohort (p=0.05).

CONCLUSION

This study observed an increased prevalence of LTBI and FI among older children and young adults recently exposed to infectious TB in the household. In addition to awareness of coughing etiquette and general hygiene, expanding access to TB preventive therapy to all HHCs, including older children, may be beneficial to achieve TB elimination by 2035.

Indoleamine 2, 3-Dioxygenase-Mediated Tryptophan Catabolism: A Leading Star or Supporting Act in the Tuberculosis and HIV Pas-de-Deux?

Progression from latency to active Tuberculosis (TB) disease is mediated by incompletely understood host immune factors. The definitive characteristic of progressive human immunodeficiency virus (HIV) disease is a severe loss in number and function of T lymphocytes. Among the many possible mediators of T lymphocyte loss and ineffective function is the activity of the immune-modulatory enzyme indoleamine 2,3-dioxygenase (IDO). IDO is the rate-limiting enzyme converting tryptophan to kynurenine. IDO activity was initially recognized to mediate tolerance at the foeto-maternal interface. Recently, IDO activity has also been noted to play a critical role in immune tolerance to pathogens. Studies of host immune and metabolic mediators have found IDO activity significantly elevated in HIV and TB disease. In this review, we explore the link between IDO-mediated tryptophan catabolism and the presence of active TB disease in HIV-infected patients. We draw attention to increased IDO activity as a key factor marking the progression from latent to active TB disease in HIV-infected patients.

Treatment of latent TB Infection and the risk of tuberculosis after solid organ transplantation: Comprehensive review

BACKGROUND

Mycobacterium tuberculosis disease may occur after treatment of latent TB infection (LTBI). Prompted by a case of reactivation TB disease in a solid organ transplant (SOT) recipient who received LTBI treatment, we reviewed the literature to examine outcomes, adverse effects, resistance, and treatment choices of tuberculosis after LTBI therapy.

METHODS

MEDLINE and Web of Science from inception to 5/2019 were reviewed using key words "latent tuberculosis infection" and "SOT" or "transplantation." The search yielded nine cases, 41 cohort studies and six randomized controlled trials (RCT).

RESULTS

Cohort and RCT demonstrated significant reduction in TB disease among transplanted patients who received LTBI therapy; only 56/2651 (2.1%) SOT patients developed TB after LTBI therapy. Adverse drug reactions occurred in 149/1148 (12.9%) and 73/641 (11.4%) of cohort and RCT patients, respectively. Among liver recipients, 56/266 (21%) developed side effects, of which half (29/56, 51.8%) was INH-related. There was no reported INH resistance.

CONCLUSIONS

Latent TB infection treatment is efficacious in SOT recipients at risk of TB disease. However, tuberculosis may still occur despite LTBI treatment. Hepatotoxicity associated with LTBI therapy is infrequent, although more commonly observed among liver recipients.

Marine Natural Products and Drug Resistance in Latent Tuberculosis

Pyrazinamide (PZA) is the only drug for the elimination of latent Mycobacterium tuberculosis (MTB) isolates. However, due to the increased number of PZA-resistance, the chances of the success of global TB elimination seems to be more prolonged. Recently, marine natural products (MNPs) as an anti-TB agent have received much attention, where some compounds extracted from marine sponge, Haliclona sp. exhibited strong activity under aerobic and hypoxic conditions. In this study, we screened articles from 1994 to 2019 related to marine natural products (MNPs) active against latent MTB isolates. The literature was also mined for the major regulators to map them in the form of a pathway under the dormant stage. Five compounds were found to be more suitable that may be applied as an alternative to PZA for the better management of resistance under latent stage. However, the mechanism of actions behind these compounds is largely unknown. Here, we also applied synthetic biology to analyze the major regulatory pathway under latent TB that might be used for the screening of selective inhibitors among marine natural products (MNPs). We identified key regulators of MTB under latent TB through extensive literature mining and mapped them in the form of regulatory pathway, where SigH is negatively regulated by RshA. PknB, RshA, SigH, and RNA polymerase (RNA-pol) are the major regulators involved in MTB survival under latent stage. Further studies are needed to screen MNPs active against the main regulators of dormant MTB isolates. To reduce the PZA resistance burden, understanding the regulatory pathways may help in selective targets of MNPs from marine natural sources.

The effectiveness and cost-effectiveness of screening for latent tuberculosis among migrants in the EU/EEA: a systematic review

Migrants account for a large and growing proportion of tuberculosis (TB) cases in low-incidence countries in the European Union/European Economic Area (EU/EEA) which are primarily due to reactivation of latent TB infection (LTBI). Addressing LTBI among migrants will be critical to achieve TB elimination. Methods: We conducted a systematic review to determine effectiveness (performance of diagnostic tests, efficacy of treatment, uptake and completion of screening and treatment) and a second systematic review on cost-effectiveness of LTBI screening programmes for migrants living in the EU/EEA. Results: We identified seven systematic reviews and 16 individual studies that addressed our aims. Tuberculin skin tests and interferon gamma release assays had high sensitivity (79%) but when positive, both tests poorly predicted the development of active TB (incidence rate ratio: 2.07 and 2.40, respectively). Different LTBI treatment regimens had low to moderate efficacy but were equivalent in preventing active TB. Rifampicin-based regimens may be preferred because of lower hepatotoxicity (risk ratio = 0.15) and higher completion rates (82% vs 69%) compared with isoniazid. Only 14.3% of migrants eligible for screening completed treatment because of losses along all steps of the LTBI care cascade. Limited economic analyses suggest that the most cost-effective approach may be targeting young migrants from high TB incidence countries. Discussion: The effectiveness of LTBI programmes is limited by the large pool of migrants with LTBI, poorly predictive tests, long treatments and a weak care cascade. Targeted LTBI programmes that ensure high screening uptake and treatment completion will have greatest individual and public health benefit.

Integrated Care for Latent Tuberculosis Infection (LTBI) at a Primary Health Care Facility for Refugees in Winnipeg, Canada: A Mixed-Methods Evaluation

Although Canada has one of the lowest tuberculosis incidence rates in the world, certain groups are disproportionately affected, including foreign born people from high incidence countries. The Winnipeg Regional Health Authority has initiated a process to decentralize latent tuberculosis infection (LTBI) management at primary care clinics in Winnipeg. One of these clinics is BridgeCare Clinic which provides services to government-assisted refugees. The present study describes the BridgeCare Clinic LTBI program and reviews program outcomes from January 2015 to October 2016. Refugees at BridgeCare Clinic receive comprehensive care, including LTBI screening and treatment. The LTBI program is managed by physicians, nurse practitioners, and primary care nurses under a patient-centered model of care. An accessible interpretation service, education to clients, and laboratory sampling at the clinic with free IGRA testing are important components of the program. Anonymized data on client outcomes were statistically analyzed and qualitative interviews were conducted with senior staff. During the study period, 274 IGRA tests were ordered with 158 negative results (57.7%) and 101 positive results (36.9%). Of 45 clients eligible (from January to December 2015) for LTBI treatment, 11 (24.4%) declined to receive treatment and 34 (75.6%) started treatment. Twenty-seven (79.4%) clients completed treatment, 3 (8.8%) clients moved out of province, and 4 (11.8%) did not complete treatment. The most recent World Health Organization strategy for tuberculosis control calls for integrated, patient-centered care and prevention. Aligned with these WHO recommendations, our experience suggests that LTBI care and treatment can be delivered effectively in a primary care setting using an integrated patient-centered approach.

Incidence of tuberculosis and the need of prophylactic treatment in persons living with HIV in Stockholm during the era of anti-retroviral therapy 1996-2013

BACKGROUND

The aim of this observational cohort study was to determine the incidence and risk factors of active tuberculosis (TB) in persons living with HIV in a low endemic setting over a 17-year time period when combination antiretroviral therapy (ART) has been available. We thereby aimed to understand the usefulness of TB chemoprophylaxis among HIV patients with latent TB.

METHODS

All 2127 adult patients diagnosed with HIV January 1996-December 2013 at the Karolinska University Hospital in Stockholm County were eligible. After exclusion of 259 patients transferred to other clinics, 1868 were followed until TB diagnosis, death or end of study period (December 2013). The median follow-up time was 7.9 years (interquartile range, 3.9-11.5).

RESULTS

Active TB was diagnosed in 92 patients, corresponding to an incidence rate of 6.2 cases (95% CI 5.1-7.6) per 1000 person-years with a significant decline over time. The majority (52%) of TB cases were diagnosed within 1 month from HIV diagnosis. Being a migrant from a TB-endemic region, was the only patient characteristic associated with significantly higher risk of active TB (Hazard Ration, HR: 8.54, 95% confidence interval, CI: 3.09-23.61 in a multivariate regression analysis controlling for route of HIV transmission, year of HIV diagnosis and CD4-cell count and viral load at HIV diagnosis. The number needed to treat to prevent one case of TB among patients in this high-risk group was 22 (95% CI 26-47).

CONCLUSION

The incidence of active TB in persons living with HIV in Stockholm County declined significantly after the introduction of ART but was still 80 times higher than in the general population at the end of the study period. The therapeutic gain of chemoprophylaxis in low endemic settings should be weighed against costs and side effects.

The Capacity of Mycobacterium tuberculosis To Survive Iron Starvation Might Enable It To Persist in Iron-Deprived Microenvironments of Human Granulomas

This study was conducted to investigate the role of iron deprivation in the persistence of Mycobacterium tuberculosis. We present evidence of iron restriction in human necrotic granulomas and demonstrate that under iron starvation M. tuberculosis persists, refractive to antibiotics and capable of restarting replication when iron is made available. Transcriptomics and metabolomic analyses indicated that the persistence of M. tuberculosis under iron starvation is dependent on strict control of endogenous Fe utilization and is associated with upregulation of pathogenicity and intrinsic antibiotic resistance determinants. M. tuberculosis mutants compromised in their ability to survive Fe starvation were identified. The findings of this study advance the understanding of the physiological settings that may underpin the chronicity of human tuberculosis (TB) and are relevant to the design of effective antitubercular therapies.

One-third of the world population may harbor persistent M. tuberculosis, causing an asymptomatic infection that is refractory to treatment and can reactivate to become potentially lethal tuberculosis disease. However, little is known about the factors that trigger and maintain M. tuberculosis persistence in infected individuals. Iron is an essential nutrient for M. tuberculosis growth. In this study, we show, first, that in human granulomas the immune defense creates microenvironments in which M. tuberculosis likely experiences drastic Fe deprivation and, second, that Fe-starved M. tuberculosis is capable of long-term persistence without growth. Together, these observations suggest that Fe deprivation in the lung might trigger a state of persistence in M. tuberculosis and promote chronic TB. We also identified vulnerabilities of iron-restricted persistent M. tuberculosis, which can be exploited for the design of new antitubercular therapies.

Prevalence and risk factors of latent tuberculosis infection in Africa: a systematic review and meta-analysis protocol

INTRODUCTION

Latent tuberculosis infection (LTBI) remains a major public health problem and one of the major contributors to the pool of active tuberculosis cases. The true burden of LTBI in Africa is not known. Early modelling studies estimate that over 33% of the world's population is infected with latent tuberculosis. We propose conducting a systematic review and a meta-analysis to evaluate the burden and risk factors of LTBI in Africa reported in studies from 2000 to 2017.

METHODS AND ANALYSIS

We will include cross-sectional studies, cohort studies and case-control studies estimating either tuberculin skin test (TST) or interferon-gamma release assay (IGRA) confirmed prevalence of LTBI and associated risk factors among people in African countries. A comprehensive search of relevant literature will be conducted on electronic databases using common and medical subject heading (MeSH) terms for LTBI, and an African search filter. Risk of bias will be evaluated by assessing all qualifying full-text articles for quality and eligibility using a quality score assessment tool. Standardised data extraction will be carried out after which prevalence estimates will be pooled using random-effects models in Stata V.13. Where there is sufficient data , subgroup meta-analyses will be conducted by risk factors including participant's age group, occupation, location and HIV status. This systematic review will be reported according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses Protocols 2015 Statement.

ETHICS AND DISSEMINATION

No ethical issues were foreseen given that this was a protocol for a systematic review of published studies. The results of this study will be published in a peer-reviewed journal and presented at conferences.

TRIAL REGISTRATION NUMBER

Systematic review registration: PROSPERO CRD42016037997.

The outcome of a cohort of tuberculin-positive predominantly South Asian new entrants aged 16-34 to the UK: Blackburn 1989-2001

SETTING

Blackburn, Hyndburn and Ribble Valley Local Government areas of England and Wales, the former a high tuberculosis (TB) prevalence district.

BACKGROUND

The incidence of tuberculosis in new entrants aged 16-34 with positive tuberculin skin tests but normal chest X-rays after initial entry is not definitely known, and was previously estimated from cross-sectional national surveys and derived data for the 2006 and 2011 NICE economic appraisals of new entrant TB screening.

METHODS

New entrants aged 16-34 years predominantly from South Asia (India, Pakistan and Bangladesh), with tuberculin tests inappropriately positive for their BCG history were identified for the years 1989-2001 inclusive from a new entrant database. These entrants were compared with the current GP registration database to see if local residence could be confirmed and the local TB notification database to October 2008. Survival analysis was carried out using Kaplan-Meier survival curves and a Cox Regression model.

RESULTS

Four hundred and seventy-nine such new entrants with normal initial chest X-rays were identified. Of these 402 (84%) registered with a General Practitioner in East Lancashire for a period of time and could be followed up by this study. The crude incidence density of active TB amongst these individuals with latent disease was 1297 per 100 000 person-years (95% CI; 991-1698 per 100 000 person-years). After 10 and 15 years of follow-up 13.5 and 16.3% of individuals, respectively, had progressed on to active disease.

CONCLUSION

This patient-derived, rather than estimated, data shows a minimum risk of TB disease of 16.3% at 15 years. The 2006 NICE economic appraisal, suggested that treatment for latent TB infection (LTBI) was cost-effective when the incidence of clinical TB over 15 years surpassed 18% in these populations. The 2011 NICE economic appraisal reduced this to 12% active TB over 15 years, and showed that at 16% active TB over 15 years a single interferon gamma release assay was the most cost-effective strategy. Further cohort studies are urgently needed to confirm or revise the assumptions behind the 2011 NICE economic appraisal.