Perspectives for personalized therapy for patients with multidrug-resistant tuberculosis

Identifying risk factors for recurrent multidrug resistant tuberculosis based on patient's record data from 2016 to 2021: retrospective study

Globally, the prevalence of multidrug-resistant tuberculosis (MDR-TB) has been increasing recently. This is a major public health concern, as MDR-TB is more difficult to treat and has poorer outcomes compared to drug-sensitive tuberculosis. The main objective of the study was to identify risk factors for recurrent multidrug-resistant tuberculosis, at Alert Specialized Hospital, Addis Ababa, by using different parametric shared frailty models. From January 2016 to December 2021, a retrospective study was conducted on MDR-TB patients at Alert Specialized Hospital in Addis Ababa. The data for the study were collected from the medical records of MDR-TB patients at the hospital during this time period. Gamma and inverse-Gaussian shared frailty models were used to analyze the dataset, with the exponential, Weibull, and lognormal distributions included as baseline hazard functions. The data were analyzed using R statistical software. The median recurrence time of the patients was 12 months, and 149 (34.3%) had recurrences. The clustering effect was statistically significant for multiple drug-resistant tuberculosis patients' recurrence. According to the Weibull-Inverse-Gaussian model, factors that reduced time to MDR-TB recurrence included lower weight (ɸ = 0.944), smoking (ɸ = 0.045), alcohol use (ɸ = 0.631), hemoptysis (ɸ = 0.041), pneumonia (ɸ = 0.564), previous anti-TB treatment (ɸ = 0.106), rural residence (ɸ = 0.163), and chronic diseases like diabetes (ɸ = 0.442) were associated with faster recurrence. While, higher education (ɸ = 3.525) and age (ɸ = 1.021) extended time to recurrence. For weight increment, smokers and alcohol users, clinical complications of hemoptysis and pneumonia, patients with pulmonary disease who had a history of previous anti-TB treatment, and being rural residents are prognostic factors. There was a significant clustering effect at the Alert Specialized Hospital in Addis Ababa, Ethiopia. The Weibull-Inverse Gaussian Shared Frailty Model was chosen as the best model for predicting the time to recurrence of MDR-TB.

Targeting Mycobacterium tuberculosis iron-scavenging tools: a recent update on siderophores inhibitors

Among the various bacterial infections, tuberculosis (TB) remains a life-threatening infectious disease responsible as the most significant cause of mortality and morbidity worldwide. The co-infection of human immunodeficiency virus (HIV) in association with TB burdens the healthcare system substantially. Notably, M.tb possesses defence against most antitubercular antibiotic drugs, and the efficacy of existing frontline anti-TB drugs is waning. Also, new and recurring cases of TB from resistant bacteria such as multidrug-resistant TB (MDR), extensively drug-resistant TB (XDR), and totally drug-resistant TB (TDR) strains are increasing. Hence, TB begs the scientific community to explore the new therapeutic class of compounds with their novel mechanism. M.tb requires iron from host cells to sustain, grow, and carry out several biological processes. M.tb has developed strategic methods of acquiring iron from the surrounding environment. In this communication, we discuss an overview of M.tb iron-scavenging tools. Also, we have summarized recently identified MbtA and MbtI inhibitors, which prevent M.tb from scavenging iron. These iron-scavenging tool inhibitors have the potential to be developed as anti-TB agents/drugs.

Implementation of targeted next-generation sequencing for the diagnosis of drug-resistant tuberculosis in low-resource settings: a programmatic model, challenges, and initial outcomes

Targeted next-generation sequencing (tNGS) from clinical specimens has the potential to become a comprehensive tool for routine drug-resistance (DR) prediction of Mycobacterium tuberculosis complex strains (MTBC), the causative agent of tuberculosis (TB). However, TB mainly affects low- and middle-income countries, in which the implementation of new technologies have specific needs and challenges. We propose a model for programmatic implementation of tNGS in settings with no or low previous sequencing capacity/experience. We highlight the major challenges and considerations for a successful implementation. This model has been applied to build NGS capacity in Namibia, an upper middle-income country located in Southern Africa and suffering from a high-burden of TB and TB-HIV, and we describe herein the outcomes of this process.

Targeting mycobacterial membranes and membrane proteins: Progress and limitations

Among the various bacterial infections, tuberculosis continues to hold center stage. Its causative agent, Mycobacterium tuberculosis, possesses robust defense mechanisms against most front-line antibiotic drugs and host responses due to their complex cell membranes with unique lipid molecules. It is now well-established that bacteria change their membrane composition to optimize their environment to survive and elude drug action. Thus targeting membrane or membrane components is a promising avenue for exploiting the chemical space focussed on developing novel membrane-centric anti-bacterial small molecules. These approaches are more effective, non-toxic, and can attenuate resistance phenotype. We present the relevance of targeting the mycobacterial membrane as a practical therapeutic approach. The review highlights the direct and indirect targeting of membrane structure and function. Direct membrane targeting agents cause perturbation in the membrane potential and can cause leakage of the cytoplasmic contents. In contrast, indirect membrane targeting agents disrupt the function of membrane-associated proteins involved in cell wall biosynthesis or energy production. We discuss the chronological chemical improvements in various scaffolds targeting specific membrane-associated protein targets, their clinical evaluation, and up-to-date account of their ''mechanisms of action, potency, selectivity'' and limitations. The sources of anti-TB drugs/inhibitors discussed in this work have emerged from target-based identification, cell-based phenotypic screening, drug repurposing, and natural products. We believe this review will inspire the exploration of uncharted chemical space for informing the development of new scaffolds that can inhibit novel mycobacterial membrane targets.

Can digital adherence technologies reduce inequity in tuberculosis treatment success? Evidence from a randomised controlled trial

INTRODUCTION

Tuberculosis (TB) is a global health emergency and low treatment adherence among patients is a major barrier to ending the TB epidemic. The WHO promotes digital adherence technologies (DATs) as facilitators for improving treatment adherence in resource-limited settings. However, limited research has investigated whether DATs improve outcomes for high-risk patients (ie, those with a high probability of an unsuccessful outcome), leading to concerns that DATs may cause intervention-generated inequality.

METHODS

We conducted secondary analyses of data from a completed individual-level randomised controlled trial in Nairobi, Kenya during 2016-2017, which evaluated the average intervention effect of a novel DAT-based behavioural support programme. We trained a causal forest model to answer three research questions: (1) Was the effect of the intervention heterogeneous across individuals? (2) Was the intervention less effective for high-risk patients? nd (3) Can differentiated care improve programme effectiveness and equity in treatment outcomes?

RESULTS

We found that individual intervention effects-the percentage point reduction in the likelihood of an unsuccessful treatment outcome-ranged from 4.2 to 12.4, with an average of 8.2. The intervention was beneficial for 76% of patients, and most beneficial for high-risk patients. Differentiated enrolment policies, targeted at high-risk patients, have the potential to (1) increase the average intervention effect of DAT services by up to 28.5% and (2) decrease the population average and standard deviation (across patients) of the probability of an unsuccessful treatment outcome by up to 8.5% and 31.5%, respectively.

CONCLUSION

This DAT-based intervention can improve outcomes among high-risk patients, reducing inequity in the likelihood of an unsuccessful treatment outcome. In resource-limited settings where universal provision of the intervention is infeasible, targeting high-risk patients for DAT enrolment is a worthwhile strategy for programmes that involve human support sponsors, enabling them to achieve the highest possible impact for high-risk patients at a substantially improved cost-effectiveness ratio.

Transcontinental spread and evolution of Mycobacterium tuberculosis W148 European/Russian clade toward extensively drug resistant tuberculosis

Transmission-driven multi-/extensively drug resistant (M/XDR) tuberculosis (TB) is the largest single contributor to human mortality due to antimicrobial resistance. A few major clades of the Mycobacterium tuberculosis complex belonging to lineage 2, responsible for high prevalence of MDR-TB in Eurasia, show outstanding transnational distributions. Here, we determined factors underlying the emergence and epidemic spread of the W148 clade by genome sequencing and Bayesian demogenetic analyses of 720 isolates from 23 countries. We dated a common ancestor around 1963 and identified two successive epidemic expansions in the late 1980s and late 1990s, coinciding with major socio-economic changes in the post-Soviet Era. These population expansions favored accumulation of resistance mutations to up to 11 anti-TB drugs, with MDR evolving toward additional resistances to fluoroquinolones and second-line injectable drugs within 20 years on average. Timescaled haplotypic density analysis revealed that widespread acquisition of compensatory mutations was associated with transmission success of XDR strains. Virtually all W148 strains harbored a hypervirulence-associated ppe38 gene locus, and incipient recurrent emergence of prpR mutation-mediated drug tolerance was detected. The outstanding genetic arsenal of this geographically widespread M/XDR strain clade represents a “perfect storm” that jeopardizes the successful introduction of new anti-M/XDR-TB antibiotic regimens.

An outbreak of the multidrug-resistant Mycobacterium tuberculosis lineage W148 has spread widely across Russia, Central Asia and Europe. Here, the authors use whole genome sequences of ~700 isolates of this lineage collected over ~20 years to analyze its spread, evolution of drug resistance, and impact of compensatory mutations.

Semi-Automated Therapeutic Drug Monitoring as a Pillar toward Personalized Medicine for Tuberculosis Management

Standard tuberculosis (TB) management has failed to control the growing number of drug-resistant TB cases worldwide. Therefore, innovative approaches are required to eradicate TB. Model-informed precision dosing and therapeutic drug monitoring (TDM) have become promising tools for adjusting anti-TB drug doses corresponding with individual pharmacokinetic profiles. These are crucial to improving the treatment outcome of the patients, particularly for those with complex comorbidity and a high risk of treatment failure. Despite the actual benefits of TDM at the bedside, conventional TDM encounters several hurdles related to laborious, time-consuming, and costly processes. Herein, we review the current practice of TDM and discuss the main obstacles that impede it from successful clinical implementation. Moreover, we propose a semi-automated TDM approach to further enhance precision medicine for TB management.

Application of Next Generation Sequencing for Diagnosis and Clinical Management of Drug-Resistant Tuberculosis: Updates on Recent Developments in the Field

The World Health Organization’s End TB Strategy prioritizes universal access to an early diagnosis and comprehensive drug susceptibility testing (DST) for all individuals with tuberculosis (TB) as a key component of integrated, patient-centered TB care. Next generation whole genome sequencing (WGS) and its associated technology has demonstrated exceptional potential for reliable and comprehensive resistance prediction for Mycobacterium tuberculosis isolates, allowing for accurate clinical decisions. This review presents a descriptive analysis of research describing the potential of WGS to accelerate delivery of individualized care, recent advances in sputum-based WGS technology and the role of targeted sequencing for resistance detection. We provide an update on recent research describing the mechanisms of resistance to new and repurposed drugs and the dynamics of mixed infections and its potential implication on TB diagnosis and treatment. Whilst the studies reviewed here have greatly improved our understanding of recent advances in this arena, it highlights significant challenges that remain. The wide-spread introduction of new drugs in the absence of standardized DST has led to rapid emergence of drug resistance. This review highlights apparent gaps in our knowledge of the mechanisms contributing to resistance for these new drugs and challenges that limit the clinical utility of next generation sequencing techniques. It is recommended that a combination of genotypic and phenotypic techniques is warranted to monitor treatment response, curb emerging resistance and further dissemination of drug resistance.

Has the Time Come for Systematic Therapeutic Drug Monitoring of First-Line and WHO Group A Antituberculosis Drugs?

ABSTRACT

Tuberculosis (TB) is a major global health issue, with approximately 10 million people being infected each year, and is the leading cause of mortality from infectious disease, with 1.5 million deaths a year. Optimal TB treatment requires a combination of drugs for an adequate treatment duration owing to persistent organisms, hardly accessible infection sites, and a high risk of resistance selection. Long-term therapy increases the risk of patients' loss of adherence, adverse drug reactions, and drug-drug interactions, potentially leading to treatment failure. The high interpatient variability of TB drug exposure is another point eliciting interest in therapeutic drug monitoring (TDM) to optimize treatment. Studies reporting clinically relevant exposure thresholds, which might be proposed as targets toward treatment personalization, are discussed. Practical TDM strategies have also been reported to circumvent issues related to delayed drug absorption and the need for multiple samples when evaluating the area under the curve of drug concentrations. The need for treatment individualization is further emphasized because of the development of multidrug-resistant TB or extensively drug-resistant TB. Finally, the willingness to shorten the treatment duration while maintaining success is also a driver for ensuring adequate exposure to TB drugs with TDM. The aim of the present review was to underline the role of TDM in drug-susceptible TB and World Health Organization group A TB drugs.

Novel treatments in multidrug-resistant tuberculosis

The management of multidrug-resistant tuberculosis (TB) is associated with low treatment success, high mortality and failure rates. New drugs and novel short-therapeutic regimens have only recently helped overcome these obstacles. We carried out a narrative literature review aimed at summarizing the scientific evidence on the recent therapeutic advances in the field of drug-resistant TB. Experimental and observational studies on novel (i.e. bedaquiline, delamanid, pretomanid) drugs and novel regimens and the main pharmacological characteristics of the newest compounds are described. We also highlight the main scientific evidence on therapeutic strategies complementary to standard chemotherapy (i.e. new approaches to drug delivery, host-directed therapy, surgery, new collapse therapy, rehabilitation, and palliative care).

Modelling the global burden of drug-resistant tuberculosis avertable by a post-exposure vaccine

There have been notable advances in the development of vaccines against active tuberculosis (TB) disease for adults and adolescents. Using mathematical models, we seek to estimate the potential impact of a post-exposure TB vaccine, having 50% efficacy in reducing active disease, on global rifampicin-resistant (RR-) TB burden. In 30 countries that together accounted for 90% of global RR-TB incidence in 2018, a future TB vaccine could avert 10% (95% credible interval: 9.7-11%) of RR-TB cases and 7.3% (6.6-8.1%) of deaths over 2020-2035, with India, China, Indonesia, Pakistan, and the Russian Federation having the greatest contribution. This impact would increase to 14% (12-16%) and 31% (29-33%) respectively, when combined with improvements in RR-TB diagnosis and treatment relative to a scenario of no vaccine and no such improvements. A future TB vaccine could have important implications for the global control of RR-TB, especially if implemented alongside enhancements in management of drug resistance.

Therapeutic drug monitoring in patients with tuberculosis and concurrent medical problems

INTRODUCTION

Therapeutic drug monitoring (TDM) has been recommended for treatment optimization in tuberculosis (TB) but is only is used in certain countries e.g. USA, Germany, the Netherlands, Sweden and Tanzania. Recently, new drugs have emerged and PK studies in TB are continuing, which contributes further evidence for TDM in TB. The aim of this review is to provide an update on drugs used in TB, treatment strategies for these drugs, and TDM to support broader implementation.

AREAS COVERED

This review describes the different drug classes used for TB, multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB), along with their pharmacokinetics, dosing strategies, TDM and sampling strategies. Moreover, the review discusses TDM for patient TB and renal or liver impairment, patients co-infected with HIV or hepatitis, and special patient populations - children and pregnant women.

EXPERT OPINION

TB treatment has a long history of using 'one size fits all.' This has contributed to treatment failures, treatment relapses, and the selection of drug-resistant isolates. While challenging in resource-limited circumstances, TDM offers the clinician the opportunity to individualize and optimize treatment early in treatment. This approach may help to refine treatment and thereby reduce adverse effects and poor treatment outcomes. Funding, training, and randomized controlled trials are needed to advance the use of TDM for patients with TB.

Perspective for Precision Medicine for Tuberculosis

Tuberculosis is a bacterial infectious disease that is mainly transmitted from human to human via infectious aerosols. Currently, tuberculosis is the leading cause of death by an infectious disease world-wide. In the past decade, the number of patients affected by tuberculosis has increased by ~20 percent and the emergence of drug-resistant strains of Mycobacterium tuberculosis challenges the goal of elimination of tuberculosis in the near future. For the last 50 years, management of patients with tuberculosis has followed a standardized management approach. This standardization neglects the variation in human susceptibility to infection, immune response, the pharmacokinetics of drugs, and the individual duration of treatment needed to achieve relapse-free cure. Here we propose a package of precision medicine-guided therapies that has the prospect to drive clinical management decisions, based on both host immunity and M. tuberculosis strains genetics. Recently, important scientific discoveries and technological advances have been achieved that provide a perspective for individualized rather than standardized management of patients with tuberculosis. For the individual selection of best medicines and host-directed therapies, personalized drug dosing, and treatment durations, physicians treating patients with tuberculosis will be able to rely on these advances in systems biology and to apply them at the bedside.

Multidrug-resistant Mycobacterium tuberculosis: a report of cosmopolitan microbial migration and an analysis of best management practices

Background

Tuberculosis (TB) control is a primary global health priority but the goal to eliminate TB is being threatened by the increase in incidence of multidrug-resistant tuberculosis (MDR-TB). With this series of seven MDR-TB cases in migrant patients with identical Mycobacterium tuberculosis strains we aim to illustrate the challenges encountered during therapy and follow-up: language barriers, access to care for migrant patients, depression due to isolation, adverse reactions to the treatment, management of pediatric TB, further contact tracing. We also discuss best practices for the management of complex MDR-TB cases in settings with low overall TB incidence focusing on modern diagnostic assays and an individualized and an interdisciplinary therapeutic approach.

Methods

We describe a case series of seven consecutively diagnosed MDR-TB patients, six of them treated at our tertiary care hospital between May 2018 and March 2020. Epidemiologic data was gained by semi-structured patient interviews and reconstruction of the migration route. The origin of the cluster was confirmed by genotyping of the TB-strains.

Results

Six related patients were diagnosed with pulmonary MDR-TB between May and August 2018. All had a positive Interferon-Gamma-Release Assay (IGRA), in five patients sputum microscopy was positive for acid-fast bacilli (AFB). The genetic and phenotypical drug susceptibility test did not match with MDR-TB strains from an East-African origin. The index patient was identified through genetical fingerprinting. By changing the therapy to a modern MDR-TB regime and using an interdisciplinary and culture-sensitive approach, all patients improved clinically and radiologically.

Conclusion

Human migration plays an important role for the global spread of MDR-TB in low incidence countries. Early case detection and adequate treatment are key to prevention of outbreaks. Especially language barriers and complex migration routes make genotyping of TB-strains a crucial tool to identify cases clusters, the potential index patient and transmission dynamics. We are fortunate enough to experience times in which new TB-antibiotics were made available and in which molecular assays revolutionized TB-diagnostics. We need to take advantage of that and develop personalized therapies for patients suffering from drug resistant TB.

Polymersomes Eradicating Intracellular Bacteria

Mononuclear phagocytes such as monocytes, tissue-specific macrophages, and dendritic cells are primary actors in both innate and adaptive immunity. These professional phagocytes can be parasitized by intracellular bacteria, turning them from housekeepers to hiding places and favoring chronic and/or disseminated infection. One of the most infamous is the bacteria that cause tuberculosis (TB), which is the most pandemic and one of the deadliest diseases, with one-third of the world's population infected and an average of 1.8 million deaths/year worldwide. Here we demonstrate the effective targeting and intracellular delivery of antibiotics to infected macrophages both in vitro and in vivo, using pH-sensitive nanoscopic polymersomes made of PMPC-PDPA block copolymer. Polymersomes showed the ability to significantly enhance the efficacy of the antibiotics killing Mycobacterium bovis, Mycobacterium tuberculosis, and another established intracellular pathogen, Staphylococcus aureus. Moreover, they demonstrated to easily access TB-like granuloma tissues-one of the harshest environments to penetrate-in zebrafish models. We thus successfully exploited this targeting for the effective eradication of several intracellular bacteria, including M. tuberculosis, the etiological agent of human TB.

Host-Directed Therapy as a Novel Treatment Strategy to Overcome Tuberculosis: Targeting Immune Modulation

Tuberculosis (TB) is one of the leading causes of mortality and morbidity, particularly in developing countries, presenting a major threat to the public health. The currently recommended long term treatment regimen with multiple antibiotics is associated with poor patient compliance, which in turn, may contribute to the emergence of multi-drug resistant TB (MDR-TB). The low global treatment efficacy of MDR-TB has highlighted the necessity to develop novel treatment options. Host-directed therapy (HDT) together with current standard anti-TB treatments, has gained considerable interest, as HDT targets novel host immune mechanisms. These immune mechanisms would otherwise bypass the antibiotic bactericidal targets to kill Mycobacterium tuberculosis (Mtb), which may be mutated to cause antibiotic resistance. Additionally, host-directed therapies against TB have been shown to be associated with reduced lung pathology and improved disease outcome, most likely via the modulation of host immune responses. This review will provide an update of host-directed therapies and their mechanism(s) of action against Mycobacterium tuberculosis.

Molecular modeling of a series of dehydroquinate dehydratase type II inhibitors of Mycobacterium tuberculosis and design of new binders

Tuberculosis, caused by Mycobacterium tuberculosis (M. tuberculosis), is still responsible for a large number of fatal cases, especially in developing countries with alarming rates of incidence and prevalence worldwide. Mycobacterium tuberculosis has a remarkable ability to develop new resistance mechanisms to the conventional antimicrobials treatment. Because of this, there is an urgent need for novel bioactive compounds for its treatment. The dehydroquinate dehydratase II (DHQase II) is considered a key enzyme of shikimate pathway, and it can be used as a promising target for the design of new bioactive compounds with antibacterial action. The aim of this work was the construction of QSAR models to aid the design of new potential DHQase II inhibitors. For that purpose, various molecular modeling approaches, such as activity cliff, QSAR models and computer-aided ligand design were utilized. A predictive in silico 4D-QSAR model was built using a database comprising 86 inhibitors of DHQase II, and the model was used to predict the activity of the designed ligands. The obtained model proved to predict well the DHQase II inhibition for an external validation dataset ([Formula: see text] = 0.72). Also, the Activity Cliff analysis shed light on important structural features applied to the ligand design.

Tuberculosis, HIV, and viral hepatitis diagnostics in eastern Europe and central Asia: high time for integrated and people-centred services

Globally, high rates (and in the WHO European region an increasing prevalence) of co-infection with tuberculosis and HIV and HIV and hepatitis C virus exist. In eastern European and central Asian countries, the tuberculosis, HIV, and viral hepatitis programmes, including diagnostic services, are separate vertical structures. In this Personal View, we consider underlying reasons for the poor integration for these diseases, particularly in the WHO European region, and how to address this with an initial focus on diagnostic services. In part, this low integration has reflected different diagnostic development histories, global funding sources, and sample types used for diagnosis (eg, typically sputum for tuberculosis and blood for HIV and hepatitis C). Cooperation between services improved as patients with tuberculosis needed routine testing for HIV and vice versa, but financial, infection control, and logistical barriers remain. Multidisease diagnostic platforms exist, but to be used optimally, appropriate staff training and sensible understanding of different laboratory and infection control risks needs rapid implementation. Technically these ideas are all feasible. Poor coordination between these vertical systems remains unhelpful. There is a need to increase political and operational integration of diagnostic and treatment services and bring them closer to patients.

Treatment of Drug-Resistant Tuberculosis. An Official ATS/CDC/ERS/IDSA Clinical Practice Guideline

Background: The American Thoracic Society, U.S. Centers for Disease Control and Prevention, European Respiratory Society, and Infectious Diseases Society of America jointly sponsored this new practice guideline on the treatment of drug-resistant tuberculosis (DR-TB). The document includes recommendations on the treatment of multidrug-resistant TB (MDR-TB) as well as isoniazid-resistant but rifampin-susceptible TB.Methods: Published systematic reviews, meta-analyses, and a new individual patient data meta-analysis from 12,030 patients, in 50 studies, across 25 countries with confirmed pulmonary rifampin-resistant TB were used for this guideline. Meta-analytic approaches included propensity score matching to reduce confounding. Each recommendation was discussed by an expert committee, screened for conflicts of interest, according to the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) methodology.Results: Twenty-one Population, Intervention, Comparator, and Outcomes questions were addressed, generating 25 GRADE-based recommendations. Certainty in the evidence was judged to be very low, because the data came from observational studies with significant loss to follow-up and imbalance in background regimens between comparator groups. Good practices in the management of MDR-TB are described. On the basis of the evidence review, a clinical strategy tool for building a treatment regimen for MDR-TB is also provided.Conclusions: New recommendations are made for the choice and number of drugs in a regimen, the duration of intensive and continuation phases, and the role of injectable drugs for MDR-TB. On the basis of these recommendations, an effective all-oral regimen for MDR-TB can be assembled. Recommendations are also provided on the role of surgery in treatment of MDR-TB and for treatment of contacts exposed to MDR-TB and treatment of isoniazid-resistant TB.

Management of drug-resistant tuberculosis

Drug-resistant tuberculosis is a major public health concern in many countries. Over the past decade, the number of patients infected with Mycobacterium tuberculosis resistant to the most effective drugs against tuberculosis (ie, rifampicin and isoniazid), which is called multidrug-resistant tuberculosis, has continued to increase. Globally, 4·6% of patients with tuberculosis have multidrug-resistant tuberculosis, but in some areas, like Kazakhstan, Kyrgyzstan, Moldova, and Ukraine, this proportion exceeds 25%. Treatment for patients with multidrug-resistant tuberculosis is prolonged (ie, 9-24 months) and patients with multidrug-resistant tuberculosis have less favourable outcomes than those treated for drug-susceptible tuberculosis. Individualised multidrug-resistant tuberculosis treatment with novel (eg, bedaquiline) and repurposed (eg, linezolid, clofazimine, or meropenem) drugs and guided by genotypic and phenotypic drug susceptibility testing can improve treatment outcomes. Some clinical trials are evaluating 6-month regimens to simplify management and improve outcomes of patients with multidrug-resistant tuberculosis. Here we review optimal diagnostic and treatment strategies for patients with drug-resistant tuberculosis and their contacts.

Monitoring Treatment of Childhood Tuberculosis and the Role of Therapeutic Drug Monitoring

Most children tolerate the first-line antibiotics used to treat Mycobacterium tuberculosis (TB) very well. The most common adverse effect is gastrointestinal distress unrelated to hepatotoxicity; the latter is seen in less than 1% of children. Despite the infrequency of hepatotoxicity, the potential long-term impact of hepatic insufficiency dictates that all children receiving antimycobacterial therapy should be evaluated periodically by symptom screening and physical examination. Routine measurement of transaminases in previously healthy, asymptomatic children is discouraged, as up to 40% of children will have transient, asymptomatic transaminase elevation that should not alter clinical management; measurement of serum liver enzymes is reserved for children who develop symptoms and those with existing liver disease or taking other potentially hepatotoxic drugs. Caregivers and personnel distributing directly-observed therapy need to be cognizant of potential drug toxicities and have a clear understanding of what to do if a child develops symptoms. There are substantial inter-patient variations in serum antibiotic concentrations when the same milligram per kilogram dose is given to different children of varying ages and sizes, reflecting differences in drug absorption and metabolism. While these variations may not impact the outcome of previously healthy children with mild disease, outcomes for children with human immunodeficiency virus infection or severe disease can be worse if sub-therapeutic drug concentrations are achieved. Therapeutic drug monitoring, wherein serum drug concentrations are used to optimize medication doses, should be considered for children with severe disease or if there is concern about alterations in drug absorption or metabolism.

Towards tailored regimens in the treatment of drug-resistant tuberculosis: a retrospective study in two Italian reference Centres

Background

The increased incidence of drug-resistant TB is a major challenge for effective TB control. Limited therapeutic options and poor treatment outcomes of DR-TB may increase drug-resistance rates. The objective of the study is to retrospectively compare MDR-TB and pre-XDR-TB treatment regimens and outcomes in two large TB reference centres in Italy from January 2000 to January 2015.

Methods

A retrospective, multicentre study was conducted at the Regional TB Reference Centre Villa Marelli Institute (Milan) and at the Reference Center for MDR-TB and HIV-TB, Eugenio Morelli Hospital (Sondalo). The supra-national Reference Laboratory in Milan performed DST. Inclusion criteria were: age ≥ 18 and culture-confirmed diagnosis of MDR- or pre-XDR TB. Chi-square or Fisher exact test was used to detect differences in the comparison between treatment outcomes, therapeutic regimens, and drug-resistances. Computations were performed with STATA 15.

Results

A total of 134 patients were selected. Median (IQR) age at admission was 33 (26–41) years and 90 patients (67.2%) were male. Pulmonary TB was diagnosed in 124 (92.5%) patients. MDR- and pre-XDR-TB cases were 91 (67.9%) and 43 (32.1%), respectively. The WHO shorter MDR-TB regimen could have been prescribed in 16/84 (19.1%) patients. Treatment success was not statistically different between MDR- and pre-XDR-TB (81.3% VS. 81.4%; P = 0.99). Mortality in MDR-TB and pre-XDR-TB groups was 4.4 and 9.3%, respectively (P = 0.2). Median duration of treatment was 18 months and a total of 110 different regimens were administered. Exposure to linezolid, meropenem, and amikacin was associated with a better outcome in both groups (P = 0.001, P < 0.001, and P = 0.004, respectively).

Conclusions

Tailored treatment regimens based on DST results can achieve successful outcomes in patients with pre-XDR-TB.

Potential drug-drug interactions between antiretroviral therapy and treatment regimens for multi-drug resistant tuberculosis: Implications for HIV care of MDR-TB co-infected individuals

HIV-positive TB co-infected patients are at increased risk of multidrug-resistant (MDR)-TB compared to HIV-negative patients. Co-treatment of MDR-TB and HIV is common particularly in Sub-Saharan Africa where the co-morbidity is endemic. We discuss potential cellular metabolic pathway-mediated drug-drug interactions and the possible effect on HIV treatment outcomes of commonly prescribed antiretroviral therapy.

Role and value of whole genome sequencing in studying tuberculosis transmission

BACKGROUND

Tuberculosis (TB) remains a serious public health threat worldwide. Theoretically ultimate resolution of whole genome sequencing (WGS) for Mycobacterium tuberculosis complex (MTBC) strain classification makes this technology very attractive for epidemiological investigations.

OBJECTIVES

To summarize the evidence available in peer-reviewed publications on the role and place of WGS in detection of TB transmission.

SOURCES

A total of 69 peer-reviewed publications identified in Pubmed database.

CONTENT

Evidence from >30 publications suggests that a cut-off value of fewer than six single nucleotide polymorphisms between strains efficiently excludes cases that are not the result of recent transmission and could be used for the identification of drug-sensitive isolates involved in direct human-to-human TB transmission. Sensitivity of WGS to identify epidemiologically linked isolates is high, reaching 100% in eight studies with specificity (17%-95%) highly dependent on the settings. Drug resistance and specific phylogenetic lineages may be associated with accelerated mutation rates affecting genetic distances. WGS can be potentially used to distinguish between true relapses and re-infections but in high-incidence low-diversity settings this would require consideration of epidemiological links and minority alleles. Data from four studies looking into within-host diversity highlight a need for developing criteria for acceptance or rejection of WGS relatedness results depending on the proportion of minority alleles.

IMPLICATIONS

WGS will potentially allow for more targeted public health actions preventing unnecessary investigations of false clusters. Consensus on standardization of raw data quality control processing criteria, analytical pipelines and reporting language is yet to be reached.

Improving the rates of Aspergillus detection: an update on current diagnostic strategies

INTRODUCTION

The spectrum of disease caused by Aspergillus spp. is dependent on the immune system of the host, and ranges from invasive aspergillosis (IA) to chronic pulmonary aspergillosis (CPA). Early and reliable diagnosis of Aspergillus disease is important to decrease associated morbidity and mortality. Areas covered: The following review will give an update on current diagnostic strategies for the diagnosis of IA and CPA. Expert commentary: Several new diagnostics for IA (including point-of-care tests) are now available to complement galactomannan testing. In particular, immunoPET/MRI imaging may be a promising approach for diagnosing IA in the near future. Notably, nearly all new biomarkers and tests for IA have been evaluated in the hematology setting only. Validation of biomarkers and tests is therefore needed for the increasing proportion of patients who develop IA outside the hematology setting. As an important first step, reliable definitions of IA are needed for non-hematology settings as clinical presentation and radiologic findings differ in these settings. CPA diagnosis is based on a combination of radiological findings in chest CT, mycological evidence (e.g. by the Aspergillus-specific IgG assay), exclusion of alternative diagnosis and chronicity. ([18F]FDG) PET/CT and immuno PET/MRI imaging are promising new imaging approaches.

Current research toward optimizing dosing of first-line antituberculosis treatment

Introduction: Drug concentrations in tuberculosis patients on standard regimens vary widely with clinically important consequences.

Areas covered: We review the available literature identifying factors correlated with pharmacokinetic variability of antituberculosis drugs. Based on population pharmacokinetic models and the weight, height, and sex distributions in a large data base of African tuberculosis patients, we propose simplified weight-based doses of the available fixed dose combination(FDC) for adults with drug susceptible tuberculosis. Emerging studies will support optimized weight-based dosing for children. Other sources of important pharmacokinetic variability include genetic variants, drug-drug interactions, formulation quality, and methods of preparation and administration.

Expert commentary: Optimized weight band-based dosing will result in more equitable distribution of drug exposures by weight. The use of high doses of isoniazid in patients with drug-resistant tuberculosis would be safer and more effective if a feasible test was developed to allow stratified dosing according to acetylator type. There is an urgent need for more suitable formulations of many second-line drugs for children. The adoption of new technologies and efficient FDC design may allow further advances for patients and treatment programs. Lastly, current efforts to ensure adequate quality of antituberculosis drug products are not preventing the use of substandard products to treat patients with tuberculosis.

Analysis of the clinical antibacterial and antituberculosis pipeline

This analysis of the global clinical antibacterial pipeline was done in support of the Global Action Plan on Antimicrobial Resistance. The study analysed to what extent antibacterial and antimycobacterial drugs for systemic human use as well as oral non-systemic antibacterial drugs for Clostridium difficile infections were active against pathogens included in the WHO priority pathogen list and their innovativeness measured by their absence of cross-resistance (new class, target, mode of action). As of July 1, 2018, 30 new chemical entity (NCE) antibacterial drugs, ten biologics, ten NCEs against Mycobacterium tuberculosis, and four NCEs against C difficile were identified. Of the 30 NCEs, 11 are expected to have some activity against at least one critical priority pathogen expressing carbapenem resistance. The clinical pipeline is dominated by derivatives of established classes and most development candidates display limited innovation. New antibacterial drugs without pre-existing cross-resistance are under-represented and are urgently needed, especially for geographical regions with high resistance rates among Gram-negative bacteria and M tuberculosis.

Toward the understanding of human tuberculosis

Content List ‐ Read more articles from the symposium: “The 10th International Conference on the Pathogenesis of Mycobacterial Infections”.