Host and Microbial Predictors of Childhood Extrathoracic Tuberculosis and Tuberculosis Meningitis

Age-specific Clinical Presentation and Risk Factors for Extrapulmonary Tuberculosis Disease in Children

BACKGROUND

Clinical presentation for extrapulmonary tuberculosis (EPTB) in children can be variable and nonspecific, leading to delayed diagnosis, disease and death. We describe the age-specific clinical presentation and identify risk factors for EPTB among children in Pakistan.

METHODS

In 2015-2016 in 4 facilities in Sindh, Pakistan, children were diagnosed with TB either through bacteriologic confirmation or clinical-radiologic criteria. EPTB comprised any form of TB disease that did not involve the lungs. Among children with TB disease, we report demographics, clinical characteristics and symptoms, family medical history and diagnostic test results for children with and without EPTB. We conduct age-specific regression analyses to identify factors associated with an EPTB diagnosis among children age 0-4, 5-9 and 10-14 years.

RESULTS

A total of 1163 children were diagnosed with TB disease, of which 157 (13.5%) had EPTB. Of those, 46 (29.3%) were 0-4, 53 (33.8%) were 5-9 and 58 (36.9%) were 10-14 years old. Of children with EPTB, the most frequently reported sites were lymph node (113, 72.4%) and abdominal (31, 19.9%). Weight loss was associated with an increased risk of EPTB in the 0-4-year-old (adjusted odds ratio: 2.80, 95% confidence interval: 1.05-7.47) and 10-14-year-old (adjusted odds ratio: 2.79, 95% confidence interval: 1.28-6.07) groups, and the presence of cough was associated with a decreased risk of EPTB.

CONCLUSIONS

This study provides new knowledge about age-specific clinical presentation and risk factors of EPTB in children in Pakistan. Our results can help to optimize clinical algorithms designed to achieve a timely diagnosis in children with EPTB along with improved treatment outcomes.

Use of Xpert MTB/RIF and Xpert Ultra in extrapulmonary tuberculosis

INTRODUCTION

Tuberculosis (TB) remains a major global health burden. There still remains a large gap between the notified and estimated incident cases. Extrapulmonary (EP) TB represents 15% of all TB cases and the diagnosis is more challenging due to the paucity of the organism. Smear microscopy is often insensitive and culture methods are prolonged. With the introduction of Xpert MTB/RIF and more recently Xpert Ultra, this has changed TB diagnostics by providing a rapid accessible platform to diagnose TB and identify rifampicin resistance within 2 h.

AREAS COVERED

The diagnostic accuracy and the clinical role of Xpert MTB/RIF and Xpert Ultra in the different forms of EPTB.

EXPERT OPINION

Whilst significant advances have been made in TB diagnostics, there is still a need to optimize the diagnostic yield of Xpert MTB/RIF and Xpert Ultra in EPTB samples. Research is needed to facilitate standardization and optimal preparation of samples as well as understanding the role of Xpert MTB/RIF and Xpert Ultra in different burden settings. Alongside the current GeneXpert platform, the launch of rapid second-line drug resistance polymerase chain reactions and whole genome sequencing may help tackle the global health burden with a more comprehensive diagnostic approach and appropriate treatment.

Bacterial Genotyping of Central Nervous System Tuberculosis in South Africa: Heterogenic Mycobacterium tuberculosis Infection and Predominance of Lineage 4

Tuberculous meningitis (TBM), the most severe extrapulmonary manifestation of tuberculosis, is caused by the pathogen Mycobacterium tuberculosis The M. tuberculosis complex includes seven lineages, all described to harbor a unique geographical dissemination pattern and clinical presentation. In this study, we set out to determine whether a certain M. tuberculosis lineage demonstrated tropism to cause TBM in patients from Cape Town, South Africa. DNA was extracted from formalin-fixed paraffin-embedded central nervous system (CNS) tissue from a unique neuropathological cohort of 83 TBM patients, collected between 1975 and 2012. M. tuberculosis lineages 1, 2, 3, and 4 were determined using an allele-specific PCR and Sanger sequencing. Of the 83 patient specimens tested, bacterial characterization could be performed on 46 specimens (55%). M. tuberculosis lineage 4 was present in 26 patient specimens (56%), and non-lineage 4 was identified in 10 cases (22%). Moreover, genomic heterogeneity was detected in the CNS specimens of 7 adults and 3 children. We could show that infection of the CNS is not restricted to a single M. tuberculosis lineage and that even young children with rapid progression of disease can harbor more than one M. tuberculosis lineage in the CNS.

Tuberculosis susceptibility and protection in children

Children represent both a clinically important population susceptible to tuberculosis and a key group in whom to study intrinsic and vaccine-induced mechanisms of protection. After exposure to Mycobacterium tuberculosis, children aged under 5 years are at high risk of progressing first to tuberculosis infection, then to tuberculosis disease and possibly disseminated forms of tuberculosis, with accompanying high risks of morbidity and mortality. Children aged 5-10 years are somewhat protected, until risk increases again in adolescence. Furthermore, neonatal BCG programmes show the clearest proven benefit of vaccination against tuberculosis. Case-control comparisons from key cohorts, which recruited more than 15 000 children and adolescents in total, have identified that the ratio of monocytes to lymphocytes, activated CD4 T cell count, and a blood RNA signature could be correlates of risk for developing tuberculosis. Further studies of protected and susceptible populations are necessary to guide development of novel tuberculosis vaccines that could facilitate the achievement of WHO's goal to eliminate deaths from tuberculosis in childhood.

Tuberculous meningitis

Tuberculosis remains a global health problem, with an estimated 10.4 million cases and 1.8 million deaths resulting from the disease in 2015. The most lethal and disabling form of tuberculosis is tuberculous meningitis (TBM), for which more than 100,000 new cases are estimated to occur per year. In patients who are co-infected with HIV-1, TBM has a mortality approaching 50%. Study of TBM pathogenesis is hampered by a lack of experimental models that recapitulate all the features of the human disease. Diagnosis of TBM is often delayed by the insensitive and lengthy culture technique required for disease confirmation. Antibiotic regimens for TBM are based on those used to treat pulmonary tuberculosis, which probably results in suboptimal drug levels in the cerebrospinal fluid, owing to poor blood-brain barrier penetrance. The role of adjunctive anti-inflammatory, host-directed therapies - including corticosteroids, aspirin and thalidomide - has not been extensively explored. To address this deficit, two expert meetings were held in 2009 and 2015 to share findings and define research priorities. This Review summarizes historical and current research into TBM and identifies important gaps in our knowledge. We will discuss advances in the understanding of inflammation in TBM and its potential modulation; vascular and hypoxia-mediated tissue injury; the role of intensified antibiotic treatment; and the importance of rapid and accurate diagnostics and supportive care in TBM.

Early diagnosis and effective treatment regimens are the keys to tackle antimicrobial resistance in tuberculosis (TB): A report from Euroscicon's international TB Summit 2016

To say that tuberculosis (TB) has regained a strong foothold in the global human health and wellbeing scenario would be an understatement. Ranking alongside HIV/AIDS as the top reason for mortality due to a single infectious disease, the impact of TB extends far into socio-economic context worldwide. As global efforts led by experts and political bodies converge to mitigate the predicted outcome of growing antimicrobial resistance, the academic community of students, practitioners and researchers have mobilised to develop integrated, inter-disciplinary programmes to bring the plans of the former to fruition. Enabling this crucial requirement for unimpeded dissemination of scientific discovery was the TB Summit 2016, held in London, United Kingdom. This report critically discusses the recent breakthroughs made in diagnostics and treatment while bringing to light the major hurdles in the control of the disease as discussed in the course of the 3-day international event. Conferences and symposia such as these are the breeding grounds for successful local and global collaborations and therefore must be supported to expand the understanding and outreach of basic science research.

Pediatric Extrapulmonary Tuberculosis: Clinical Spectrum, Risk Factors and Diagnostic Challenges in a Low Prevalence Region

BACKGROUND

Children are at higher risk of tuberculosis (TB) dissemination and extrapulmonary disease, contributing greatly to TB-associated morbidity and long-term sequelae. However, there are very few studies that assess the impact and clinical spectrum of pediatric extrapulmonary TB (EPTB) in low-prevalence regions.

METHODS

Children <18 years of age diagnosed with TB in Madrid region (2005-2013) were reviewed. We compared the epidemiology, clinical characteristics and the performance of diagnostic tests in childhood extrapulmonary and pulmonary disease. We performed a multivariate logistic regression to identify factors associated with EPTB.

RESULTS

During the study period, 93 of 526 pediatric TB cases had EPTB (17.7%). The most common site was lymphatic TB (34.5%). The source case was not identified in most extrapulmonary cases, contrary to pulmonary TB (28% vs. 63.3%; P < 0.001). The tuberculin-skin-test induration was smaller in EPTB cases (<5 mm 22% vs. 5%; P < 0.001), but the sensitivity of interferon-gamma-release-assays was similar (76.9% vs. 79.4%). Children with EPTB presented higher rate of bacteriologic confirmation (66% vs. 49.4%; P < 0.01), and higher incidence of multidrug resistant TB (8.2% vs. 1.6%; P = 0.03). Complications were present in 40.2% extrapulmonary cases. EPTB was associated with the child's foreign origin [odds ratio (OR) 2.3 (1.1-5.3)], immune disorders [OR 5.8 (1.9-17.1)] and drug resistance [OR 2.4 (1.1-5.4)].

CONCLUSIONS

In our low-prevalence region, childhood EPTB was linked to immigrant status, immune disorders and drug resistance, and presented high rate of complications. Our study underscores the relevance of improved diagnostic tools and systematic TB screening in high risk populations.

Tuberculosis incidence is high in HIV-infected African children but is reduced by co-trimoxazole and time on antiretroviral therapy

BACKGROUND

There are few data on tuberculosis (TB) incidence in HIV-infected children on antiretroviral therapy (ART). Observational studies suggest co-trimoxazole prophylaxis may prevent TB, but there are no randomized data supporting this. The ARROW trial, which enrolled HIV-infected children initiating ART in Uganda and Zimbabwe and included randomized cessation of co-trimoxazole prophylaxis, provided an opportunity to estimate the incidence of TB over time, to explore potential risk factors for TB, and to evaluate the effect of stopping co-trimoxazole prophylaxis.

METHODS

Of 1,206 children enrolled in ARROW, there were 969 children with no previous TB history. After 96 weeks on ART, children older than 3 years were randomized to stop or continue co-trimoxazole prophylaxis; 622 were eligible and included in the co-trimoxazole analysis. Endpoints, including TB, were adjudicated blind to randomization by an independent endpoint review committee (ERC). Crude incidence rates of TB were estimated and potential risk factors, including age, sex, center, CD4, weight, height, and initial ART strategy, were explored in multivariable Cox proportional hazards models.

RESULTS

After a median of 4 years follow-up (3,632 child-years), 69 children had an ERC-confirmed TB diagnosis. The overall TB incidence was 1.9/100 child-years (95% CI, 1.5-2.4), and was highest in the first 12 weeks following ART initiation (8.8/100 child-years (5.2-13.4) versus 1.2/100 child-years (0.8-1.6) after 52 weeks). A higher TB risk was independently associated with younger age (<3 years), female sex, lower pre-ART weight-for-age Z-score, and current CD4 percent; fewer TB diagnoses were observed in children on maintenance triple nucleoside reverse transcriptase inhibitor (NRTI) ART compared to standard non-NRTI + 2NRTI. Over the median 2 years of follow-up, there were 20 ERC-adjudicated TB cases among 622 children in the co-trimoxazole analysis: 5 in the continue arm and 15 in the stop arm (hazard ratio (stop: continue) = 3.0 (95% CI, 1.1-8.3), P = 0.028). TB risk was also independently associated with lower current CD4 percent (P <0.001).

CONCLUSIONS

TB incidence varies over time following ART initiation, and is particularly high during the first 3 months post-ART, reinforcing the importance of TB screening prior to starting ART and use of isoniazid preventive therapy once active TB is excluded. HIV-infected children continuing co-trimoxazole prophylaxis after 96 weeks of ART were diagnosed with TB less frequently, highlighting a potentially important role of co-trimoxazole in preventing TB.