What is thwarting tuberculosis prevention in high-burden settings?

Repetitive Aerosol Exposure Promotes Cavitary Tuberculosis and Enables Screening for Targeted Inhibitors of Extensive Lung Destruction

Background

Cavitation is a serious consequence of tuberculosis. We tested the hypothesis that repetitive exposure to the same total bacterial burden of Mycobacterium tuberculosis drives greater lung destruction than a single exposure. We also tested whether inhibition of endogenous matrix metalloproteinase-1 (MMP-1) may inhibit cavitation during tuberculosis.

Methods

Over a 3-week interval, we infected rabbits with either 5 aerosols of 500 colony-forming units (CFU) of M. tuberculosis or a single aerosol of 2500 CFU plus 4 sham aerosols. We administered the MMP-1 inhibitor cipemastat (100 mg/kg daily) during weeks 5-10 to a subset of the animals.

Results

Repetitive aerosol infection produced greater lung inflammation and more cavities than a single aerosol infection of the same bacterial burden (75% of animals vs 25%). Necropsies confirmed greater lung pathology in repetitively exposed animals. For cipemastat-treated animals, there was no significant difference in cavity counts, cavity volume, or disease severity compared to controls.

Conclusions

Our data show that repetitive aerosol exposure with M. tuberculosis drives greater lung damage and cavitation than a single exposure. This suggests that human lung destruction due to tuberculosis may be exacerbated in settings where individuals are repeatedly exposed. MMP-1 inhibition with cipemastat did not prevent the development of cavitation in our model.

The Application of T.SPOT-TB Assay for Early Diagnosis of Active Tuberculosis in Chronic Kidney Disease Patients Receiving Immunosuppressive Treatment

Background: The current study investigated the clinical application of the T-SPOT.TB assay for detecting tuberculosis (TB) infection in chronic kidney disease patients treated with immunosuppressive therapy. Methods: Clinical data from 91 patients were retrospectively analyzed. The rate of positive T-SPOT.TB results and spot numbers were compared before and after treatment. Clinical characteristics that may affect the test results were also investigated. Results: Two active TB cases were observed after immunosuppressive treatment, and eight patients with negative T-SPOT.TB results at baseline had positive results after treatment. No significant changes in spot numbers were observed for patients who were positive at baseline. Compared with pretreatment baseline, patients who received medium/high doses of corticosteroids had a greater number of T-SPOT.TB positive results (p = 0.016) and CFP-10 spots (p = 0.041) after treatment. For patients who received combination therapy with medium/high doses of corticosteroids, the T-SPOT.TB positive rate (p = 0.046) and CFP-10 spot number (p = 0.041) were increased after treatment, with no significant changes in the total number of spots or ESAT-6 spots. For those who received combination therapy with low doses of corticosteroids and those who received single immunosuppressive medication, there were no significant differences in the T-SPOT.TB positive rate, total spot number, or numbers of ESAT-6 and CFP-10 spots. Conclusion: The increase in positive T-SPOT.TB results was mainly associated with medium/high doses of glucocorticoids. The active TB cases might represent new infections. Regular monitoring using the T-SPOT.TB assay will help in the early detection of active TB.

Barriers to the implementation of isoniazid preventive therapy for tuberculosis in children in endemic settings: A review

Isoniazid preventive therapy is one of the key interventions in reducing the risk of active disease among children exposed to tuberculosis. However, initiation and maintenance of this treatment is poor in many areas. This review summarises the existing literature on barriers to implementation of isoniazid preventive therapy for tuberculosis in children in endemic settings. MEDLINE, EMBASE and CINAHL databases were used to search for primary research studies published between 1998 and 2018, specifically mentioning isoniazid preventive therapy, tuberculosis and children. Barriers identified in most study settings included absence of parental risk perception, health-care worker knowledge gaps and treatment access. Focusing on patient-centred care, enhancing community and health-care worker education and securing stable medication supply to effectively deliver this therapy is crucial in order to reduce childhood morbidity and mortality from tuberculosis.

The role of agency in the implementation of Isoniazid Preventive Therapy (IPT): Lessons from oMakoti in uMgungundlovu District, South Africa

Introduction

In response to revisions in global and national policy in 2011, six-month isoniazid preventive therapy (IPT) became freely available as a preventive measure for people living with HIV in the uMgungundlovu District of KwaZulu-Natal province, South Africa. Given a difference in uptake and completion by sex, we sought to explore the reasons why Zulu women were more likely to accept and complete IPT compared to men in an effort to inform future implementation.

Methods

Utilising a community-based participatory research approach and ethnographic methods, we undertook 17 individual and group interviews, and met regularly with grassroots community advisory teams in three Zulu communities located in uMgungundlovu District between March 2012–December 2016.

Findings & discussion

Three categories described women’s willingness to initiate IPT: women are caregivers, women are obedient, and appearance is important. The findings suggest that the success of IPT implementation amongst clinic-utilising women of uMgungundlovu is related to the cultural gender norms of uMakoti, isiZulu for “the bride” or “the wife.” We invoke the cultural concept of inhlonipho, meaning “to show respect,” to discuss how the cultural values of uMakoti may conflict with biomedical expectations of adherence. Such conflict can result in misinterpretations by healthcare providers or patients, and lead some patients to fear the repercussions of asking questions or contemplating discontinuation with the provider, preferring instead to appear obedient. We propose a shift in emphasis from adherence-focussed strategies, characteristic of the current biomedical approach, to practices that promote patient agency in an effort to offer IPT more appropriately.

Implications

Building on existing tools, namely the harm reduction model and the use of mini-ethnography, we provide guidance on how to support women to participate as agents in the decision to initiate or continue IPT, decisions which may also impact the health and choices of the family.

Recent transmission of Mycobacterium tuberculosis in China: the implication of molecular epidemiology for tuberculosis control

Tuberculosis (TB) has remained an ongoing concern in China. The national scale-up of the Directly Observed Treatment, Short Course (DOTS) program has accelerated the fight against TB in China. Nevertheless, many challenges still remain, including the spread of drug-resistant strains, high disease burden in rural areas, and enormous rural-to-urban migrations. Whether incident active TB represents recent transmission or endogenous reactivation has helped to prioritize the strategies for TB control. Evidence from molecular epidemiology studies has delineated the recent transmission of Mycobacterium tuberculosis (M. tuberculosis) strains in many settings. However, the transmission patterns of TB in most areas of China are still not clear. Studies carried out to date could not capture the real burden of recent transmission of the disease in China because of the retrospective study design, incomplete sampling, and use of low-resolution genotyping methods. We reviewed the implementations of molecular epidemiology of TB in China, the estimated disease burden due to recent transmission of M. tuberculosis strains, the primary transmission of drug-resistant TB, and the evaluation of a feasible genotyping method of M. tuberculosis strains in circulation.

Correlates of isoniazid preventive therapy failure in child household contacts with infectious tuberculosis in high burden settings in Nairobi, Kenya - a cohort study

Background

Sub-Saharan Africa continues to document high pediatric tuberculosis (TB) burden, especially among the urban poor. One recommended preventive strategy involves tracking and isoniazid preventive therapy (IPT) for children under 5 years in close contact with infectious TB. However, sub-optimal effectiveness has been documented in diverse settings. We conducted a study to elucidate correlates to IPT strategy failure in children below 5 years in high burden settings.

Methods

A prospective longitudinal cohort study was done in informal settlings in Nairobi, where children under 5 years in household contact with recently diagnosed smear positive TB adults were enrolled. Consent was sought. Structured questionnaires administered sought information on index case treatment, socio-demographics and TB knowledge. Contacts underwent baseline clinical screening exclude TB and/or pre-existing chronic conditions. Contacts were then put on daily isoniazid for 6 months and monitored for new TB disease, compliance and side effects. Follow-up continued for another 6 months.

Results

At baseline, 428 contacts were screened, and 14(3.2%) had evidence of TB disease, hence excluded. Of 414 contacts put on IPT, 368 (88.8%) completed the 1 year follow-up. Operational challenges were reported by 258(70%) households, while 82(22%) reported side effects. Good compliance was documented in 89% (CI:80.2–96.2). By endpoint, 6(1.6%) contacts developed evidence of new TB disease and required definitive anti-tuberculosis therapy. The main factor associated with IPT failure was under-nutrition of contacts (p = 0.023).

Conclusion

Under-nutrition was associated with IPT failure for child contacts below 5 years in high burden, resource limited settings. IPT effectiveness could be optimized through nutrition support of contacts.

Electronic supplementary material

The online version of this article (10.1186/s12879-017-2719-8) contains supplementary material, which is available to authorized users.

Molecular epidemiology of Mycobacterium tuberculosis among South African gold miners

RATIONALE

HIV-associated tuberculosis remains a major health problem among the gold-mining workforce in South Africa. We postulate that high levels of recent transmission, indicated by strain clustering, are fueling the tuberculosis epidemic among gold miners.

OBJECTIVES

To combine molecular and epidemiologic data to describe Mycobacterium tuberculosis genetic diversity, estimate levels of transmission, and examine risk factors for clustering.

METHODS

We conducted a cross-sectional study of culture-positive M. tuberculosis isolates in 15 gold mine shafts across three provinces in South Africa. All isolates were subject IS6110-based restriction fragment length polymorphisms, and we performed spoligotyping analysis and combined it with basic demographic and clinical information.

MEASUREMENTS AND MAIN RESULTS

Of the 1,602 M. tuberculosis patient isolates, 1,240 (78%) had genotyping data available for analysis. A highly diverse bacillary population was identified, comprising a total of 730 discrete genotypes. Four genotypic families (Latin American Mediterranean spoligotype family; W-Beijing; AH or X; and T1-T4) accounted for over 50% of all strains. Overall, 45% (560/1,240) of strains were genotypically clustered. The minimum estimate for recent transmission (n - 1 method) was 32% (range, 27-34%). There were no individual-level risk factors for clustering, apart from borderline evidence for being non-South African and having self-reported HIV infection.

CONCLUSIONS

The high M. tuberculosis genetic diversity and lack of risk factors for clustering are indicative of a universal risk for disease among gold miners and likely mixing with nonmining populations. Our results underscore the urgent need to intensify interventions to interrupt transmission across the entire gold-mining workforce in South Africa.

Rifamycins (rifampicin, rifabutin and rifapentine) compared to isoniazid for preventing tuberculosis in HIV-negative people at risk of active TB

BACKGROUND

Preventing active tuberculosis (TB) from developing in people with latent tuberculosis infection (LTBI) is important for global TB control. Isoniazid (INH) for six to nine months has 60% to 90% protective efficacy, but the treatment period is long, liver toxicity is a problem, and completion rates outside trials are only around 50%. Rifampicin or rifamycin-combination treatments are shorter and may result in higher completion rates.

OBJECTIVES

To compare the effects of rifampicin monotherapy or rifamycin-combination therapy versus INH monotherapy for preventing active TB in HIV-negative people at risk of developing active TB.

SEARCH METHODS

We searched the Cochrane Infectious Disease Group Specialized Register; Cochrane Central Register of Controlled Trials (CENTRAL); MEDLINE; EMBASE; LILACS; clinical trials registries; regional databases; conference proceedings; and references, without language restrictions to December 2012; and contacted experts for relevant published, unpublished and ongoing trials.

SELECTION CRITERIA

Randomized controlled trials (RCTs) of HIV-negative adults and children at risk of active TB treated with rifampicin, or rifamycin-combination therapy with or without INH (any dose or duration), compared with INH for six to nine months.

DATA COLLECTION AND ANALYSIS

At least two authors independently screened and selected trials, assessed risk of bias, and extracted data. We sought clarifications from trial authors. We pooled relative risks (RRs) with their 95% confidence intervals (CIs), using a random-effects model if heterogeneity was significant. We assessed overall evidence quality using the GRADE approach.

MAIN RESULTS

Ten trials are included, enrolling 10,717 adults and children, mostly HIV-negative (2% HIV-positive), with a follow-up period ranging from two to five years. Rifampicin (three/four months) vs. INH (six months) Five trials published between 1992 to 2012 compared these regimens, and one small 1992 trial in adults with silicosis did not detect a difference in the occurrence of TB over five years of follow up (one trial, 312 participants; very low quality evidence). However, more people in these trials completed the shorter course (RR 1.19, 95% CI 1.01 to 1.30; five trials, 1768 participants; moderate quality evidence). Treatment-limiting adverse events were not significantly different (four trials, 1674 participants; very low quality evidence), but rifampicin caused less hepatotoxicity (RR 0.12, 95% CI 0.05 to 0.30; four trials, 1674 participants; moderate quality evidence). Rifampicin plus INH (three months) vs. INH (six months) The 1992 silicosis trial did not detect a difference between people receiving rifampicin plus INH compared to INH alone for occurrence of active TB (one trial, 328 participants; very low quality evidence). Adherence was similar in this and a 1998 trial in people without silicosis (two trials, 524 participants; high quality evidence). No difference was detected for treatment-limiting adverse events (two trials, 536 participants; low quality evidence), or hepatotoxicity (two trials, 536 participants; low quality evidence). Rifampicin plus pyrazinamide (two months) vs. INH (six months) Three small trials published in 1994, 2003, and 2005 compared these two regimens, and two reported a low occurrence of active TB, with no statistically significant differences between treatment regimens (two trials, 176 participants; very low quality evidence) though, apart from one child from the 1994 trial, these data on active TB were from the 2003 trial in adults with silicosis. Adherence with both regimens was low with no statistically significant differences (four trials, 700 participants; very low quality evidence). However, people receiving rifampicin plus pyrazinamide had more treatment-limiting adverse events (RR 3.61, 95% CI 1.82 to 7.19; two trials, 368 participants; high quality evidence), and hepatotoxicity (RR 4.59, 95% 2.14 to 9.85; three trials, 540 participants; moderate quality evidence). Weekly, directly-observed rifapentine plus INH (three months) vs. daily, self-administered INH (nine months) A large trial conducted from 2001 to 2008 among close contacts of TB in the USA, Canada, Brazil and Spain found directly observed weekly treatment to be non-inferior to nine months self-administered INH for the incidence of active TB (0.2% vs 0.4%, RR 0.44, 95% CI 0.18 to 1.07, one trial, 7731 participants; moderate quality evidence). The directly-observed, shorter regimen had higher treatment completion (82% vs 69%, RR 1.19, 95% CI 1.16 to 1.22, moderate quality evidence), and less hepatotoxicity (0.4% versus 2.4%; RR 0.16, 95% CI 0.10 to 0.27; high quality evidence), though treatment-limiting adverse events were more frequent (4.9% versus 3.7%; RR 1.32, 95% CI 1.07 to 1.64 moderate quality evidence)

AUTHORS' CONCLUSIONS

Trials to date of shortened prophylactic regimens using rifampicin alone have not demonstrated higher rates of active TB when compared to longer regimens with INH. Treatment completion is probably higher and adverse events may be fewer with shorter rifampicin regimens. Shortened regimens of rifampicin with INH may offer no advantage over longer INH regimens. Rifampicin combined with pyrazinamide is associated with more adverse events. A weekly regimen of rifapentine plus INH has higher completion rates, and less liver toxicity, though treatment discontinuation due to adverse events is probably more likely than with INH.

Data needs for evidence-based decisions: a tuberculosis modeler's 'wish list'

Infectious disease models are important tools for understanding epidemiology and supporting policy decisions for disease control. In the case of tuberculosis (TB), such models have informed our understanding and control strategies for over 40 years, but the primary assumptions of these models--and their most urgent data needs--remain obscure to many TB researchers and control officers. The structure and parameter values of TB models are informed by observational studies and experiments, but the evidence base in support of these models remains incomplete. Speaking from the perspective of infectious disease modelers addressing the broader TB research and control communities, we describe the basic structure common to most TB models and present a 'wish list' that would improve the evidence foundation upon which these models are built. As a comprehensive TB research agenda is formulated, we argue that the data needs of infectious disease models--our primary long-term decision-making tools--should figure prominently.

Response to Comment on “Community-Wide Isoniazid Preventive Therapy Drives Drug-Resistant Tuberculosis: A Model-Based Analysis”

Our modeling work suggests that isoniazid preventive therapy (IPT) can be effective in reducing drug-sensitive tuberculosis (TB) and that the risk of IPT driving resistance can be reduced by improving the detection and rapid treatment of individuals with drug-resistant disease and by limiting IPT to those in whom the intervention will have the largest benefit.

Rifamycins (rifampicin, rifabutin and rifapentine) compared to isoniazid for preventing tuberculosis in HIV-negative people at risk of active TB

BACKGROUND

Preventing active tuberculosis (TB) from developing in people with latent tuberculosis infection (LTBI) is important for global TB control. Isoniazid (INH) for six to nine months has 60% to 90% protective efficacy, but the treatment period is long, liver toxicity is a problem, and completion rates outside trials are only around 50%. Rifampicin or rifamycin-combination treatments are shorter and may result in higher completion rates.

OBJECTIVES

To compare the effects of rifampicin monotherapy or rifamycin-combination therapy versus INH monotherapy for preventing active TB in HIV-negative people at risk of developing active TB.

SEARCH METHODS

We searched the Cochrane Infectious Disease Group Specialized Register; Cochrane Central Register of Controlled Trials (CENTRAL); MEDLINE; EMBASE; LILACS; clinical trials registries; regional databases; conference proceedings; and references, without language restrictions to December 2012; and contacted experts for relevant published, unpublished and ongoing trials.

SELECTION CRITERIA

Randomized controlled trials (RCTs) of HIV-negative adults and children at risk of active TB treated with rifampicin, or rifamycin-combination therapy with or without INH (any dose or duration), compared with INH for six to nine months.

DATA COLLECTION AND ANALYSIS

At least two authors independently screened and selected trials, assessed risk of bias, and extracted data. We sought clarifications from trial authors. We pooled relative risks (RRs) with their 95% confidence intervals (CIs), using a random-effects model if heterogeneity was significant. We assessed overall evidence quality using the GRADE approach.

MAIN RESULTS

Ten trials are included, enrolling 10,717 adults and children, mostly HIV-negative (2% HIV-positive), with a follow-up period ranging from two to five years. Rifampicin (three/four months) vs. INH (six months)Five trials published between 1992 to 2012 compared these regimens, and one small 1992 trial in adults with silicosis did not detect a difference in the occurrence of TB over five years of follow up (one trial, 312 participants; very low quality evidence). However, more people in these trials completed the shorter course (RR 1.19, 95% CI 1.01 to 1.30; five trials, 1768 participants; moderate quality evidence). Treatment-limiting adverse events were not significantly different (four trials, 1674 participants; very low quality evidence), but rifampicin caused less hepatotoxicity (RR 0.12, 95% CI 0.05 to 0.30; four trials, 1674 participants; moderate quality evidence). Rifampicin plus INH (three months) vs. INH (six months)The 1992 silicosis trial did not detect a difference between people receiving rifampicin plus INH compared to INH alone for occurrence of active TB (one trial, 328 participants; very low quality evidence). Adherence was similar in this and a 1998 trial in people without silicosis (two trials, 524 participants; high quality evidence). No difference was detected for treatment-limiting adverse events (two trials, 536 participants; low quality evidence), or hepatotoxicity (two trials, 536 participants; low quality evidence). Rifampicin plus pyrazinamide (two months) vs. INH (six months)Three small trials published in 1994, 2003, and 2005 compared these two regimens, and two reported a low occurrence of active TB, with no statistically significant differences between treatment regimens (two trials, 176 participants; very low quality evidence) though, apart from one child from the 1994 trial, these data on active TB were from the 2003 trial in adults with silicosis. Adherence with both regimens was low with no statistically significant differences (four trials, 700 participants; very low quality evidence). However, people receiving rifampicin plus pyrazinamide had more treatment-limiting adverse events (RR 3.61, 95% CI 1.82 to 7.19; two trials, 368 participants; high quality evidence), and hepatotoxicity (RR 4.59, 95% 2.14 to 9.85; three trials, 540 participants; moderate quality evidence). Weekly, directly-observed rifapentine plus INH (three months) vs. daily, self-administered INH (nine months)A large trial conducted from 2001 to 2008 among close contacts of TB in the USA, Canada, Brazil and Spain found directly observed weekly treatment to be non-inferior to nine months self-administered INH for the incidence of active TB (0.2% vs 0.4%, RR 0.44, 95% CI 0.18 to 1.07, one trial, 7731 participants; moderate quality evidence). The directly-observed, shorter regimen had higher treatment completion (82% vs 69%, RR 1.19, 95% CI 1.16 to 1.22, moderate quality evidence), and less hepatotoxicity (0.4% versus 2.4%; RR 0.16, 95% CI 0.10 to 0.27; high quality evidence), though treatment-limiting adverse events were more frequent (4.9% versus 3.7%; RR 1.32, 95% CI 1.07 to 1.64 moderate quality evidence)

AUTHORS' CONCLUSIONS

Trials to date of shortened prophylactic regimens using rifampicin alone have not demonstrated higher rates of active TB when compared to longer regimens with INH. Treatment completion is probably higher and adverse events may be fewer with shorter rifampicin regimens. Shortened regimens of rifampicin with INH may offer no advantage over longer INH regimens. Rifampicin combined with pyrazinamide is associated with more adverse events. A weekly regimen of rifapentine plus INH has higher completion rates, and less liver toxicity, though treatment discontinuation due to adverse events is probably more likely than with INH.

Tuberculosis: time for a new perspective?

Transmission of Mycobacterium tuberculosis (Mtb) continues uninterrupted. Pre-exposure vaccination remains a central focus of tuberculosis research but 25 years of follow up is needed to determine whether a novel childhood vaccination regime protects from adult disease, or like BCG assists Mtb dissemination by preventing childhood illness but not infective adult pulmonary tuberculosis. Therefore, different strategies to interrupt the life cycle of Mtb need to be explored. This personal perspective discusses alternative approaches that may be delivered in a shorter time frame.