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Recent advances in genetic manipulation such as triploid breeding and artificial selection, have rapidly emerged as valuable hatchery methodologies for enhancing seafood stocks. The Pacific oyster Magallana gigas is a leading aquaculture species worldwide and key ecosystem engineer that has received particular attention in this field of science. In light of the growing recognition of the ecological effects of intraspecific variation, oyster polyploids provide a valuable opportunity to assess whether intraspecific diversity affects physiological responses to environmental stressors. While the responses of diploid and triploid oysters to climate change have been extensively investigated, research on their sensitivity to environmental pollution remains scarce. Here, we assess whether genotypic (i.e., ploidy) variation within Magallana gigas affects physiological responses to microplastic pollution. We show that diploid and triploid M. gigas have similar clearance rates and ingest similar amounts of microplastics under laboratory-controlled condition. In addition, they exhibited similar heart rates after prolonged exposure to microplastic leachates. Our findings suggest that intraspecific variations within M. gigas ploidy does not affect oyster responses to microplastic pollution. However, regardless of ploidy, our work highlights significant adverse effects of microplastic leachates on the heart rate of M. gigas and provides evidence of microplastic ingestion in the laboratory.

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Heatwaves are increasingly severe and frequent, posing significant threats to ecosystems and human well-being. Characterised by high thermal variability, intertidal communities are particularly vulnerable to heat stress. Microbial endolithic communities that are found in marine calcifying organisms have been shown to induce shell erosion that alters shell surface colour, lowering body temperatures and increasing survival rates. Here, we investigate how the symbiotic relationship between endolithic microbes and the blue intertidal mussel Mytilus edulis mitigates thermal stress during the unprecedented 2022 atmospheric heatwave in the English Channel. Microbial infestation of the shell significantly enhanced mussel survival, particularly higher on the shore where thermal stress was greater. Using data from biomimetic temperature loggers, we predicted the expected thermal buffer and observed differences up to 3.2 °C between individuals with and without symbionts under the known conditions of the heat wave-induced mortality event. The ecological implications extend beyond individual mussels, affecting the reef-building capacity of mussels, with potential cascading effects for local biodiversity, carbon sequestration, and coastal defence. These findings emphasize the importance of understanding small-scale biotic interactions during extreme climate events and provide insights into the dynamic nature of the endolith-mussel symbiosis along a parasitic-mutualistic continuum influenced by abiotic factors.

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Calls to decolonize global health have highlighted the continued existence of colonial structures in research into diseases of public health importance particularly in low- and middle-income countries (LMICs). A key step towards restructuring the system and shaping it to local needs is equitable leadership in global health partnerships. This requires ensuring that researchers in LMICs are given the opportunity to successfully secure grant funding to lead and drive their own research based on locally defined priorities. In February 2022, the London School of Hygiene and Tropical Medicine hosted a workshop aimed at bringing together funders and early- and mid-career researchers (EMCRs) to identify funder initiatives that have worked to improve equitable leadership, to better understand barriers faced by researchers, and collectively brainstorm approaches to overcome these barriers. The workshop transcript was analyzed using a deductive thematic approach based on the workshop topic to identify key emerging themes. Barriers identified were the lack of individual and institutional level support and flawed funding structures for EMCRs in LMIC settings. Strategies on how equitable leadership can be further facilitated include institutional reforms for funders to facilitate equity, diversity, and inclusion in their partners through consultative engagement and in addition, reshaping how research priorities are defined; diversified funding streams for research organizations, building partnerships and dedicated funding for capacity building of EMCRs. Intentional advances to overcome funding barriers in global health speak directly to its decolonization. Urgently required and complex changes in practice must be intentional and do require uncomfortable shifts which will take time. Supplementary Information: The online version contains supplementary material available at 10.1186/s44263-024-00047-4.

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Drug-resistant tuberculosis (DR-TB) threatens progress in the control of TB. Mathematical models are increasingly being used to guide public health decisions on managing both antimicrobial resistance (AMR) and TB. It is important to consider bacterial heterogeneity in models as it can have consequences for predictions of resistance prevalence, which may affect decision-making. We conducted a systematic review of published mathematical models to determine the modelling landscape and to explore methods for including bacterial heterogeneity. Our first objective was to identify and analyse the general characteristics of mathematical models of DR-mycobacteria, including M. tuberculosis. The second objective was to analyse methods of including bacterial heterogeneity in these models. We had different definitions of heterogeneity depending on the model level. For between-host models of mycobacterium, heterogeneity was defined as any model where bacteria of the same resistance level were further differentiated. For bacterial population models, heterogeneity was defined as having multiple distinct resistant populations. The search was conducted following PRISMA guidelines in five databases, with studies included if they were mechanistic or simulation models of DR-mycobacteria. We identified 195 studies modelling DR-mycobacteria, with most being dynamic transmission models of non-treatment intervention impact in M. tuberculosis (n = 58). Studies were set in a limited number of specific countries, and 44% of models (n = 85) included only a single level of "multidrug-resistance (MDR)". Only 23 models (8 between-host) included any bacterial heterogeneity. Most of these also captured multiple antibiotic-resistant classes (n = 17), but six models included heterogeneity in bacterial populations resistant to a single antibiotic. Heterogeneity was usually represented by different fitness values for bacteria resistant to the same antibiotic (61%, n = 14). A large and growing body of mathematical models of DR-mycobacterium is being used to explore intervention impact to support policy as well as theoretical explorations of resistance dynamics. However, the majority lack bacterial heterogeneity, suggesting that important evolutionary effects may be missed.

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Community structure is driven by the interaction of physical processes and biological interactions that can vary across environmental gradients and the strength of top-down control is expected to vary along gradients of primary productivity. In coastal marine systems, upwelling drives regional resource availability through the bottom-up effect of nutrient subsidies. This alters rates of primary production and is expected to alter algae-herbivore interactions in rocky intertidal habitats. Despite the potential for upwelling to alter these interactions, the interaction of upwelling and grazing pressure is poorly understood, particularly for warm-temperate systems. Using in situ herbivore exclusion experiments replicated across multiple upwelling regimes, we investigated the effects of both grazing pressure, upwelling, and their interactions on the sessile invertebrate community and biomass of macroalgal communities in a warm-temperate system. The sessile invertebrate cover showed indirect effects of grazing, being consistently low where algal biomass was high at upwelling sites and at nonupwelling sites when grazers were excluded. The macroalgal cover was greater at upwelling sites when grazers were excluded and there was a strong effect of succession throughout the experimental period. Grazing effects were greater at upwelling sites, particularly during winter months. There was a nonsignificant trend toward greater grazing pressure on early than later successional stages. Our results show that the positive bottom-up effects of nutrient supply on algal production do not overwhelm top-down control in this warm-temperate system but do have knock-on consequences for invertebrates that compete with macroalgae for space. We speculate that global increases in air and sea surface temperatures in warm-temperate systems will promote top-down effects in upwelling regions by increasing herbivore metabolic and growth rates.

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Interspecific and intraspecific diversity are essential components of biodiversity with far-reaching implications for ecosystem function and service provision. Importantly, genotypic and phenotypic variation within a species can affect responses to anthropogenic pressures more than interspecific diversity. We investigated the effects of interspecific and intraspecific diversity on microplastic ingestion by two coexisting mussel species in South Africa, Mytilus galloprovincialis and Perna perna, the latter occurring as two genetic lineages. We found significantly higher microplastic abundance in M. galloprovincialis (0.54 ± 0.56 MP items g-1WW) than P. perna (0.16 ± 0.21 MP items g-1WW), but no difference between P. perna lineages. Microbeads were the predominant microplastic (76 % in P. perna, 99 % in M. galloprovincialis) and polyethylene the prevalent polymer. Interspecific differences in microplastic abundance varied across locations, suggesting diverse sources of contamination. We suggest that microplastic ingestion can be species-specific even in organisms that coexist and play similar functional roles within ecosystems.

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BACKGROUND: Tuberculosis remains a leading infectious cause of death in resource-limited settings. Effective treatment is the cornerstone of tuberculosis control, reducing mortality, recurrence and transmission. Supporting treatment adherence through facility-based observations of medication taking can be costly to providers and patients. Digital adherence technologies (DATs) may facilitate treatment monitoring and differentiated care. The ASCENT-Ethiopia study is a three-arm cluster randomised trial assessing two DATs with differentiated care for supporting tuberculosis treatment adherence in Ethiopia. This study is part of the ASCENT consortium, assessing DATs in South Africa, the Philippines, Ukraine, Tanzania and Ethiopia. The aim of this study is to determine the costs, cost-effectiveness and equity impact of implementing DATs in Ethiopia. METHODS AND DESIGN: A total of 78 health facilities have been randomised (1:1:1) into one of two intervention arms or a standard-of-care arm. Approximately 50 participants from each health facility will be enrolled on the trial. Participants in facilities randomised to the intervention arms are offered a DAT linked to the ASCENT adherence platform for daily adherence monitoring and differentiated response for those who have missed doses. Participants at standard-of-care facilities receive routine care. Treatment outcomes and resource utilisation will be measured for each participant. The primary effectiveness outcome is a composite index of unfavourable end-of-treatment outcomes (lost to follow-up, death or treatment failure) or treatment recurrence within 6 months of end-of-treatment. For the cost-effectiveness analysis, end-of-treatment outcomes will be used to estimate disability-adjusted life years (DALYs) averted. Provider and patient cost data will be collected from a subsample of 5 health facilities per study arm, 10 participants per facility (n = 150). We will conduct a societal cost-effectiveness analysis using Bayesian hierarchical models that account for the individual-level correlation between costs and outcomes as well as intra-cluster correlation. An equity impact analysis will be conducted to summarise equity efficiency trade-offs. DISCUSSION: Trial enrolment is ongoing. This paper follows the published trial protocol and describes the protocol and analysis plan for the health economics work package of the ASCENT-Ethiopia trial. This analysis will generate economic evidence to inform the implementation of DATs in Ethiopia and globally. TRIAL REGISTRATION: Pan African Clinical Trial Registry (PACTR) PACTR202008776694999. Registered on 11 August 2020,  https://pactr.samrc.ac.za/TrialDisplay.aspx?TrialID=12241 .

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Rocky shores typically exhibit a variety of sedentary and free-moving forms of epibionts associated with the shells of mussel basibionts. This paper provides a first report on epibiotic bryozoans found on shells of the invasive Mediterranean mussel, Mytilus galloprovincialis Lamarck. More than 2500 mussels were collected between December 2019 and October 2020 from rocky shores during low spring tides across the south-southeast coast of South Africa. Ten percent of these mussels hosted epibiotic bryozoans. We examined a subset of these epibiotised mussels to assess the diversity of bryozoans. Three encrusting cheilostome species were identified: Chaperia atypica n. sp., Celleporella hyalina (Linnaeus), and Hippomonavella sp. This new species is the first Chaperia with avicularia and the first South African species with ooecia. This study highlights the biological diversity of epibiotic bryozoans on mussel shells and, given their differences in microtopography, the possibility that invasive species can provide a new substratum for rare, overlooked or undescribed species of epibionts.

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The impact of climate change on biodiversity has stimulated the need to understand environmental stress responses, particularly for ecosystem engineers whose responses to climate affect large numbers of associated organisms. Distinct species differ substantially in their resilience to thermal stress but there are also within-species variations in thermal tolerance for which the molecular mechanisms underpinning such variation remain largely unclear. Intertidal mussels are well-known for their role as ecosystem engineers. First, we exposed two genetic lineages of the intertidal mussel Perna perna to heat stress treatments in air and water. Next, we ran a high throughput RNA sequencing experiment to identify differences in gene expression between the thermally resilient eastern lineage and the thermally sensitive western lineage. We highlight different thermal tolerances that concord with their distributional ranges. Critically, we also identified lineage-specific patterns of gene expression under heat stress and revealed intraspecific differences in the underlying transcriptional pathways in response to warmer temperatures that are potentially linked to the within-species differences in thermal tolerance. Beyond the species, we show how unravelling within-species variability in mechanistic responses to heat stress promotes a better understanding of global evolutionary trajectories of the species as a whole in response to changing climate.

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INTRODUCTION: Successful treatment of tuberculosis depends to a large extent on good adherence to treatment regimens, which relies on directly observed treatment (DOT). This in turn requires frequent visits to health facilities. High costs to patients, stigma and burden to the health system challenged the DOT approach. Digital adherence technologies (DATs) have emerged as possibly more feasible alternatives to DOT but there is conflicting evidence on their effectiveness and feasibility. Our primary objective is to evaluate whether the implementation of DATs with daily monitoring and a differentiated response to patient adherence would reduce poor treatment outcomes compared with the standard of care (SOC). Our secondary objectives include: to evaluate the proportion of patients lost to follow-up; to compare effectiveness by DAT type; to evaluate the feasibility and acceptability of DATs; to describe factors affecting the longitudinal engagement of patients with the intervention and to use a simple model to estimate the epidemiological impact and cost-effectiveness of the intervention from a health system perspective. METHODS AND ANALYSIS: This is a pragmatic two-arm cluster-randomised trial in the Philippines, South Africa, Tanzania and Ukraine, with health facilities as the unit of randomisation. Facilities will first be randomised to either the DAT or SOC arm, and then the DAT arm will be further randomised into medication sleeve/labels or smart pill box in a 1:1:2 ratio for the smart pill box, medication sleeve/label or the SOC respectively. We will use data from the digital adherence platform and routine health facility records for analysis. In the main analysis, we will employ an intention-to-treat approach to evaluate treatment outcomes. ETHICS AND DISSEMINATION: The study has been approved by the WHO Research Ethics Review Committee (0003296), and by country-specific committees. The results will be shared at national and international meetings and will be published in peer-reviewed journals. TRIAL REGISTRATION NUMBER: ISRCTN17706019.

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Microbial symbionts have strong potential to mediate responses to climate change. Such modulation may be particularly important in the case of hosts that modify the physical habitat structure. By transforming the habitats, ecosystem engineers alter resource availability and modulate environmental conditions which, in turn, indirectly shape the community associated with that habitat. Endolithic cyanobacteria are known to reduce the body temperatures of infested mussels and here, we assessed whether the thermal benefits of endoliths on the intertidal reef-building mussel Mytilus galloprovincialis extends to the invertebrate community utilising mussel beds as habitat. Artificial reefs of biomimetic mussels either colonised or not colonised by microbial endoliths were used to test whether infauna species (the limpet Patella vulgata, the snail Littorina littorea and mussel recruits) in a mussel bed with symbionts experience lower body temperatures than those within a bed composed of mussels without symbionts. We found that infaunal individuals benefitted from being surrounded by mussels with symbionts, an effect that may be particularly critical during intense heat stress. Indirect effects of biotic interactions, complicate our understanding of community and ecosystem responses to climate change, especially in cases involving ecosystem engineers, and accounting for them will improve our predictions.

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Environmental filtering (EF), the abiotic exclusion of species, can have first order, direct effects with cascading consequences for population dynamics, especially at range edges where abiotic conditions are suboptimal. Abiotic stress gradients associated with EF may also drive indirect second order effects, including exacerbating the effects of competitors, disease, and parasites on marginal populations because of suboptimal physiological performance. We predicted a cascade of first and second order EF-associated effects on marginal populations of the invasive mussel Mytilus galloprovincialis, plus a third order effect of EF of increased epibiont load due to second order shell degradation by endoliths. Mussel populations on rocky shores were surveyed across 850 km of the south-southeast coast of South Africa, from the species' warm-edge range limit to sites in the centre of their distribution, to quantify second order (endolithic shell degradation) and third order (number of barnacle epibionts) EF-associated effects as a function of along-shore distance from the range edge. Inshore temperature data were interpolated from the literature. Using in situ temperature logger data, we calculated the effective shore level for several sites by determining the duration of immersion and emersion. Summer and winter inshore water temperatures were linked to distance from the mussel's warm range edge (our proxy for an EF-associated stress gradient), suggesting that seasonality in temperature contributes to first order effects. The gradient in thermal stress clearly affected densities, but its influence on mussel size, shell degradation, and epibiosis was weaker. Relationships among mussel size, shell degradation, and epibiosis were more robust. Larger, older mussels had more degraded shells and more epibionts, with endolithic damage facilitating epibiosis. EF associated with a gradient in thermal stress directly limits the distribution, abundance, and size structure of mussel populations, with important indirect second and third order effects of parasitic disease and epibiont load, respectively.

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Background: The order and orientation of genes encoded by animal mitogenomes are typically conserved, although there is increasing evidence of multiple rearrangements among mollusks. The mitogenome from a Brazilian brown mussel (hereafter named B1) classified as Perna perna Linnaeus, 1758 and assembled from Illumina short-length reads revealed an unusual gene order very different from other congeneric species. Previous mitogenomic analyses based on the Brazilian specimen and other Mytilidae suggested the polyphyly of the genus Perna. Methods: To confirm the proposed gene rearrangements, we sequenced a second Brazilian P. perna specimen using the "primer-walking" method and performed the assembly using as reference Perna canaliculus. This time-consuming sequencing method is highly effective when assessing gene order because it relies on sequentially-determined, overlapping fragments. We also sequenced the mitogenomes of eastern and southwestern South African P. perna lineages to analyze the existence of putative intraspecific gene order changes as the two lineages show overlapping distributions but do not exhibit a sister relationship. Results: The three P. perna mitogenomes sequenced in this study exhibit the same gene order as the reference. CREx, a software that heuristically determines rearrangement scenarios, identified numerous gene order changes between B1 and our P. perna mitogenomes, rejecting the previously proposed gene order for the species. Our results validate the monophyly of the genus Perna and indicate a misidentification of B1.

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Euendolithic, or true-boring, cyanobacteria actively erode carbonate-containing substrata in a wide range of environments and pose significant risks to calcareous marine fauna. Their boring activities cause structural damage and increase susceptibility to disease and are projected to only intensify with global climate change. Most research has, however, focused on tropical coral systems, and limited information exists on the global distribution, diversity, and substratum specificity of euendoliths. This metastudy aimed to collate existing 16S rRNA gene surveys along with novel data from the south coast of South Africa to investigate the global distribution and genetic diversity of endoliths to identify a "core endolithic cyanobacterial microbiome" and assess global diversification of euendolithic cyanobacteria. The cyanobacterial families Phormidesmiaceae, Nodosilineaceae, Nostocaceae, and Xenococcaceae were the most prevalent, found in >92% of categories surveyed. All four known euendolith clusters were detected in both intertidal and subtidal habitats, in the North Atlantic, Mediterranean, and South Pacific oceans, across temperate latitudes, and within rock, travertine tiles, coral, shell, and coralline algae substrata. Analysis of the genetic variation within clusters revealed many organisms to be unique to substratum type and location, suggesting high diversity and niche specificity. Euendoliths are known to have important effects on their hosts. This is particularly important when hosts are globally significant ecological engineers or habitat-forming species. The findings of this study indicate high ubiquity and diversity of euendolithic cyanobacteria, suggesting high adaptability, which may lead to increased community and ecosystem-level effects with changing climatic conditions favoring the biochemical mechanisms of cyanobacterial bioerosion.

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Recruitment of mussels is a complex process with the successful arrival of individuals hinging on the availability of suitable habitats. We examined the effects of adult mussels as settlement habitat and the degree to which the suitability of habitat they offer is species-specific by comparing the recruitment success of intertidal mussels. We hypothesised that mussel recruitment and early growth are dictated by the quality of habitat offered by conspecifics adults. We used a unique experimental arena on the south coast of South Africa, where Mytilus galloprovincialis and two lineages of Perna perna co-exist. Treatments were based on the translocation of individuals of M. galloprovincialis, western- and eastern lineage of P. perna to a single site, where artificial beds were created and sampled monthly over one year. Recruit's number, their sizes and growth were greater within beds of the western lineage of Perna than eastern lineage or Mytilus beds. The results clearly demonstrate that the quality of settlement habitat offered by adult beds differs among adult lineages/species and affects rates of settlement and the early growth of recruits. This effect extends to the intraspecific level; we found greater differences in density and growth of recruits between lineages of Perna than between either lineage and M. galloprovincialis. Supplementary Information: The online version contains supplementary material available at 10.1007/s10750-022-04994-7.

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Our understanding of how anthropogenic stressors such as climate change and plastic pollution interact with biodiversity is being widened to include diversity below the species level, i.e., intraspecific variation. The emerging appreciation of the key ecological importance of intraspecific diversity and its potential loss in the Anthropocene, further highlights the need to assess the relative importance of intraspecific versus interspecific diversity. One such issue is whether a species responds as a homogenous whole to plastic pollution. Using manipulative field transplant experiments and laboratory-controlled hydrodynamic simulations, we assessed the relative effects of intraspecific and interspecific diversity on microplastic trapping in coastal biogenic habitats dominated by two key bioengineers, the brown intertidal macroalgae Fucus vesiculosus and F. guiryi. At the individual level, northern morphotypes of F. guiryi trapped more microplastics than southern individuals, and F. vesiculosus trapped more microplastics than F. guiryi. Canopy density varied among species, however, leading to reversed patterns of microplastic accumulation, with F. guiryi canopies accumulating more microplastics than those of F. vesiculosus, while no differences were observed between the canopies of F. guiryi morphotypes. We emphasize the importance of assessing the effects of intraspecific variation which, along with other crucial factors such as canopy density, flow velocity and polymer composition, modulates the extent of microplastic accumulation in coastal biogenic habitats. Our findings indicate that a realistic estimation of plastic accumulation in biogenic habitats requires an understanding of within- and between-species traits at both the individual and population levels.

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BACKGROUND: Estimates suggest that at least 30 000 children develop multidrug-resistant or rifampicin-resistant tuberculosis each year. Despite household contact management (HCM) being widely recommended, it is rarely done. METHODS: We used mathematical modelling to evaluate the potential country-level and global effects and cost-effectiveness of multidrug-resistant or rifampicin-resistant tuberculosis HCM for children younger than 15 years who are living with a person with newly diagnosed multidrug-resistant or rifampicin-resistant tuberculosis. We compared a baseline of no HCM with several HCM strategies and tuberculosis preventive therapy regimens, calculating the effect on multidrug-resistant or rifampicin-resistant tuberculosis cases, deaths, and health-system costs. All HCM strategies involved the screening of children for prevalent tuberculosis disease but with tuberculosis preventive therapy either not given or targeted dependent on age, HIV status, and result of tuberculin skin test. We evaluated the use of fluoroquinolones (ie, levofloxacin and moxifloxacin), delamanid, and bedaquiline as tuberculosis preventive therapy. FINDINGS: Compared with a baseline without HCM, HCM for all adults diagnosed with multidrug-resistant or rifampicin-resistant tuberculosis in 2019 would have entailed screening 227 000 children (95% uncertainty interval [UI]: 205 000-252 000) younger than 15 years globally, and averted 2350 tuberculosis deaths (1940-2790), costing an additional US$63 million (74-95 million). If all the children within the household who had been in contact with the person with multidrug-resistant or rifampicin-resistant tuberculosis received tuberculosis preventive therapy with levofloxacin, 5620 incident tuberculosis cases (95% UI 4540-6890) and an additional 1240 deaths (970-1540) would have been prevented. Incremental cost-effectiveness ratios were lower than half of per-capita gross domestic product for most interventions in most countries. Targeting only children younger than 5 years and those living with HIV reduced the number of incident cases and deaths averted, but improved cost-effectiveness. Tuberculosis preventive therapy with delamanid increased the effect, in terms of reduced incidence and mortality, compared with levofloxacin. INTERPRETATION: HCM for patients with multidrug-resistant or rifampicin-resistant tuberculosis is cost-effective in most settings and could avert a substantial proportion of multidrug-resistant or rifampicin-resistant tuberculosis cases and deaths in children globally. FUNDING: UK Medical Research Council.

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