Mixed infections in tuberculosis: The missing part in a puzzle

New insight in molecular detection of Mycobacterium tuberculosis

Mycobacterium tuberculosis, the causative agent of tuberculosis, is a pathogenic bacterium that has claimed millions of lives since the Middle Ages. According to the World Health Organization's report, tuberculosis ranks among the ten deadliest diseases worldwide. The presence of an extensive array of genes and diverse proteins within the cellular structure of this bacterium has provided us with a potent tool for diagnosis. While the culture method remains the gold standard for tuberculosis diagnosis, it is possible that molecular diagnostic methods, emphasis on the identification of mutation genes (e.g., rpoB and gyrA) and single nucleotide polymorphisms, could offer a safe and reliable alternative. Over the past few decades, as our understanding of molecular genetics has expanded, methods have been developed based on gene expansion and detection. These methods typically commence with DNA amplification through nucleic acid targeted techniques such as polymerase chain reaction. Various molecular compounds and diverse approaches have been employed in molecular assays. In this review, we endeavor to provide an overview of molecular assays for the diagnosis of tuberculosis with their properties (utilization, challenges, and functions). The ultimate goal is to explore the potential of replacing traditional bacterial methods with these advanced molecular diagnostic techniques.

The occurrence rate of Haarlem and Beijing genotypes among Middle Eastern isolates of multi drug resistant Mycobacterium tuberculosis: A systematic review and meta-analysis

Antibiotic resistance is a serious problem that poses a major challenge to tuberculosis control worldwide. Many developing countries still struggle with this infection in term of various aspects as it remains a major health concern. A number of developing countries are located in the Middle East, one of the world's most important regions. The control of this infection remains largely suboptimal despite intensive research in the field, and the mechanisms that lead to its progression have not yet been fully understood. Therefore, TB control must be amended through the identification of new strategies. For this reason, monitoring genetic characterizations of TB strains by molecular typing methods in different geographical regions can be important to setting local programs and global strategies to control TB infection. It is important to know the genotype of Mycobacterium tuberculosis strains to evaluate the occurrence of outbreaks and the transmission of this disease. Beijing and Haarlem genotypes are the most prevalent and, in these families, there is greater association with drug resistance, resulting in more severe forms of TB and higher levels of treatment failure than in other families. The current study is planned to systematically conduct a review using a meta-analysis to show the prevalence of Beijing and Haarlem genotypes in the Middle Eastern MDR-TB cases. M. tuberculosis strains pose particular epidemiological and clinical concerns as they can endanger tuberculosis control programs.

Tuberculosis and lung cancer: metabolic pathways play a key role

Despite the fact that some cases of tuberculosis (TB) are undiagnosed and untreated, it remains a serious global public health issue. In the diagnosis, treatment, and control of latent and active TB, there may be a lack of effectiveness. An understanding of metabolic pathways can be fundamental to treat latent TB infection and active TB disease. Rather than targeting Mycobacterium tuberculosis, the control strategies aim to strengthen host responses to infection and reduce chronic inflammation by effectively enhancing host resistance to infection. The pathogenesis and progression of TB are linked to several metabolites and metabolic pathways, and they are potential targets for host-directed therapies. Additionally, metabolic pathways can contribute to the progression of lung cancer in patients with latent or active TB. A comprehensive metabolic pathway analysis is conducted to highlight lung cancer development in latent and active TB. The current study aimed to emphasize the association between metabolic pathways of tumor development in patients with latent and active TB. Health control programs around the world are compromised by TB and lung cancer due to their special epidemiological and clinical characteristics. Therefore, presenting the importance of lung cancer progression through metabolic pathways occurring upon TB infection can open new doors to improving control of TB infection and active TB disease while stressing that further evaluations are required to uncover this correlation.

An insight to the recent advancements in detection of Mycobacterium tuberculosis using biosensors: A systematic review

Since ancient times, Tuberculosis (TB) has been a severe invasive illness that has been prevalent for thousands of years and is also known as "consumption" or phthisis. TB is the most common chronic lung bacterial illness in the world, killing over 2 million people each year, caused by Mycobacterium tuberculosis (MTB). As per the reports of WHO, in spite of technology advancements, the average rate of decline in global TB infections from 2000-2018 was only 1.6% per year, and the worldwide reduction in TB deaths was only 11%. In addition, COVID-19 pandemic has reversed years of global progress in tackling TB with fewer diagnosed cases. The majority of undiagnosed patients of TB are found in low- and middle-income countries where the GeneXpert MTB/RIF assay and sputum smear microscopy have been approved by the WHO as reference procedures for quickly detecting TB. Biosensors, like other cutting-edge technologies, have piqued researchers' interest since they offer a quick and accurate way to identify MTB. Modern integrated technologies allow for the rapid, low-cost, and highly precise detection of analytes in extremely little amounts of sample by biosensors. Here in this review, we outlined the severity of tuberculosis (TB) and the most recent developments in the biosensors sector, as well as their various kinds and benefits for TB detection. The review also emphasizes how widespread TB is and how it needs accurate diagnosis and effective treatment.

Fusarium diversity associated with diseased cereals in China, with an updated phylogenomic assessment of the genus

Fusarium species are important cereal pathogens that cause severe production losses to major cereal crops such as maize, rice, and wheat. However, the causal agents of Fusarium diseases on cereals have not been well documented because of the difficulty in species identification and the debates surrounding generic and species concepts. In this study, we used a citizen science initiative to investigate diseased cereal crops (maize, rice, wheat) from 250 locations, covering the major cereal-growing regions in China. A total of 2 020 Fusarium strains were isolated from 315 diseased samples. Employing multi-locus phylogeny and morphological features, the above strains were identified to 43 species, including eight novel species that are described in this paper. A world checklist of cereal-associated Fusarium species is provided, with 39 and 52 new records updated for the world and China, respectively. Notably, 56 % of samples collected in this study were observed to have co-infections of more than one Fusarium species, and the detailed associations are discussed. Following Koch's postulates, 18 species were first confirmed as pathogens of maize stalk rot in this study. Furthermore, a high-confidence species tree was constructed in this study based on 1 001 homologous loci of 228 assembled genomes (40 genomes were sequenced and provided in this study), which supported the "narrow" generic concept of Fusarium (= Gibberella). This study represents one of the most comprehensive surveys of cereal Fusarium diseases to date. It significantly improves our understanding of the global diversity and distribution of cereal-associated Fusarium species, as well as largely clarifies the phylogenetic relationships within the genus. Taxonomic novelties: New species: Fusarium erosum S.L. Han, M.M. Wang & L. Cai, Fusarium fecundum S.L. Han, M.M. Wang & L. Cai, Fusarium jinanense S.L. Han, M.M. Wang & L. Cai, Fusarium mianyangense S.L. Han, M.M. Wang & L. Cai, Fusarium nothincarnatum S.L. Han, M.M. Wang & L. Cai, Fusarium planum S.L. Han, M.M. Wang & L. Cai, Fusarium sanyaense S.L. Han, M.M. Wang & L. Cai, Fusarium weifangense S.L. Han, M.M. Wang & L. Cai. Citation: Han SL, Wang MM, Ma ZY, Raza M, Zhao P, Liang JM, Gao M, Li YJ, Wang JW, Hu DM, Cai L (2023). Fusarium diversity associated with diseased cereals in China, with an updated phylogenomic assessment of the genus. Studies in Mycology 104: 87-148. doi: 10.3114/sim.2022.104.02.

Clinical application value of metagenomic next-generation sequencing in the diagnosis of central nervous system infections

Objectives: The purpose of this study is to evaluate the clinical application value of metagenomic next-generation sequencing (mNGS) in central nervous system (CNS) infections. Methods: Both mNGS and routine examination of cerebrospinal fluid (CSF) samples from patients with CNS infections retrospectively analyzed the efficacy of mNGS in this cohort and were ultimately compared with a clinical diagnosis. Results: A total of 94 cases consistent with CNS infections were included in the analysis. The positive rate for mNGS is 60.6% (57/94), which is significantly higher than 20.2% (19/94; p < 0.01) detected using conventional methods. mNGS detected 21 pathogenic strains that could not be detected by routine testing. Routine tests were positive for two pathogens but negative for mNGS. The sensitivity and specificity of mNGS in the diagnosis of central nervous system infections were 89.5% and 44%, respectively, when compared with traditional tests. At discharge, 20 (21.3%) patients were cured, 55 (58.5%) patients showed improvements, five (5.3%) patients did not recover, and two (2.1%) patients died. Conclusion: mNGS has unique advantages in the diagnosis of central nervous system infections. mNGS tests can be performed when patients are clinically suspected of having a central nervous system infection but no pathogenic evidence.

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.

Detection of Mycobacterium tuberculosis multiple strains in sputum samples from patients with pulmonary tuberculosis in south western Uganda using MIRU-VNTR

Infections with multiple strains of Mycobacterium tuberculosis are now widely recognized as a common occurrence. Identification of patients infected with multiple strains provides both insight into the disease dynamics and the epidemiology of tuberculosis. Analysis of Mycobacterial Interspersed Repetitive Unit-Variable-Number Tandem Repeats (MIRU-VNTR) has been shown to be highly sensitive in detecting multiple M. tuberculosis strains even in sputum. The goal of this study was to identify cases of multiple M. tuberculosis strain infections among patients diagnosed with pulmonary tuberculosis in Southwestern Uganda and assessment of factors associated with multiple strain infections. DNA extracted directly from 78 sputum samples, each from an individual patient, was analyzed using the standard 24 loci MIRU-VNTR typing. Five (6.4%) of the 78 patients were infected with multiple strains of M. tuberculosis with all of them being the newly diagnosed cases while two-thirds of them were co-infected with HIV. Exact regression analysis projected that the natives were more likely to harbor multiple strains (OR; 0.981, 95% CI 0–7.926) as well as those with a high microbial load (OR; 0.390, 95% CI 0–3.8167). Despite these findings being not statistically significant due to the small sample size, this points to a critical component of disease dynamics that has clinical implications and emphasizes a need for a study using a larger cohort. It is also essential to study the potential factors associated with higher risk of exposure to newly diagnosed and HIV positive patients at the community level. In addition, our ability to detect multiple M. tuberculosis strains using the standard 24 loci MIRU-VNTR typing especially with allelic diversity in loci 2059 and 3171, which are excluded from the 15-locus MIRU-VNTR, lead us to recommend the use of this genotyping technique, especially in areas with tuberculosis endemicity similar to this study.

Detection of Minority Variants and Mixed Infections in Mycobacterium tuberculosis by Direct Whole-Genome Sequencing on Noncultured Specimens Using a Specific-DNA Capture Strategy

Detection of mixed Mycobacterium tuberculosis (MTB) infections is essential, particularly when resistance mutations are present in minority bacterial populations that may affect patients' disease evolution and treatment. Whole-genome sequencing (WGS) has extended the amount of key information available for the diagnosis of MTB infection, including the identification of mixed infections. Having genomic information at diagnosis for early intervention requires carrying out WGS directly on the clinical samples. However, few studies have been successful with this approach due to the low representation of MTB DNA in sputa. In this study, we evaluated the ability of a strategy based on specific MTB DNA enrichment by using a newly designed capture platform (MycoCap) to detect minority variants and mixed infections by WGS on controlled mixtures of MTB DNAs in a simulated sputum genetic background. A pilot study was carried out with 12 samples containing 98% of a DNA pool from sputa of patients without MTB infection and 2% of MTB DNA mixtures at different proportions. Our strategy allowed us to generate sequences with a quality equivalent to those obtained from culture: 62.5× depth coverage and 95% breadth coverage (for at least 20× reads). Assessment of minority variant detection was carried out by manual analysis and allowed us to identify heterozygous positions up to a 95:5 ratio. The strategy also automatically distinguished mixed infections up to a 90:10 proportion. Our strategy efficiently captures MTB DNA in a nonspecific genetic background, allows detection of minority variants and mixed infections, and is a promising tool for performing WGS directly on clinical samples. IMPORTANCE We present a new strategy to identify mixed infections and minority variants in Mycobacterium tuberculosis by whole-genome sequencing. The objective of the strategy is the direct detection in patient sputum; in this way, minority populations of resistant strains can be identified at the time of diagnosis, facilitating identification of the most appropriate treatment for the patient from the first moment. For this, a platform for capturing M. tuberculosis-specific DNA was designed to enrich the clinical sample and obtain quality sequences.

Possible Transmission Mechanisms of Mixed Mycobacterium tuberculosis Infection in High HIV Prevalence Country, Botswana

Tuberculosis caused by concurrent infection with multiple Mycobacteriumtuberculosis strains (i.e., mixed infection) challenges clinical and epidemiologic paradigms. We explored possible transmission mechanisms of mixed infection in a population-based, molecular epidemiology study in Botswana during 2012–2016. We defined mixed infection as multiple repeats of alleles at >2 loci within a discrete mycobacterial interspersed repetitive unit–variable-number tandem-repeat (MIRU-VNTR) result. We compared mixed infection MIRU-VNTR results with all study MIRU-VNTR results by considering all permutations at each multiple allele locus; matched MIRU-VNTR results were considered evidence of recently acquired strains and nonmatched to any other results were considered evidence of remotely acquired strains. Among 2,051 patients, 34 (1.7%) had mixed infection, of which 23 (68%) had recently and remotely acquired strains. This finding might support the mixed infection mechanism of recent transmission and simultaneous remote reactivation. Further exploration is needed to determine proportions of transmission mechanisms in settings where mixed infections are prevalent.

Genomic analyses of Mycobacterium tuberculosis from human lung resections reveal a high frequency of polyclonal infections

Polyclonal infections occur when at least two unrelated strains of the same pathogen are detected in an individual. This has been linked to worse clinical outcomes in tuberculosis, as undetected strains with different antibiotic resistance profiles can lead to treatment failure. Here, we examine the amount of polyclonal infections in sputum and surgical resections from patients with tuberculosis in the country of Georgia. For this purpose, we sequence and analyse the genomes of Mycobacterium tuberculosis isolated from the samples, acquired through an observational clinical study (NCT02715271). Access to the lung enhanced the detection of multiple strains (40% of surgery cases) as opposed to just using a sputum sample (0-5% in the general population). We show that polyclonal infections often involve genetically distant strains and can be associated with reversion of the patient's drug susceptibility profile over time. In addition, we find different patterns of genetic diversity within lesions and across patients, including mutational signatures known to be associated with oxidative damage; this suggests that reactive oxygen species may be acting as a selective pressure in the granuloma environment. Our results support the idea that the magnitude of polyclonal infections in high-burden tuberculosis settings is underestimated when only testing sputum samples.

Clinical and public health utility of Mycobacterium tuberculosis whole genome sequencing

The World Health Organization (WHO) estimates that around 10 million people develop tuberculosis (TB) every year, with 1.5 million deaths attributed to TB in 2019 (World Health Organization, 2020). The majority of the disease burden occurs in low-income countries, where access to diagnostics and tailored treatment remains problematic. The current COVID-19 pandemic further threatens to impact global TB control by diverting resources, reducing notifications and hence significantly increasing deaths attributable to TB (World Health Organization, 2020). Whole genome sequencing (WGS) is becoming increasingly accessible, and has particular value in the diagnosis and management of TB disease (Cabibbe et al., 2018; Meehan et al., 2019). Not only does it have the potential to give more rapid and complete information on drug-resistance, but the high discriminatory power it offers allows detection of clusters and transmission pathways, as well as likely contamination events, mixed infections and to differentiate between re-infection and relapse with much greater confidence than previous typing methods.

Overlapping prison/community tuberculosis outbreaks in Costa Rica revealed by alternative analysis of suboptimal material

Costa Rica has a low incidence of tuberculosis. Thus, identifying transmission hotspots is key to implement interventions. A tuberculosis outbreak was suspected in a prison in Costa Rica. Given the suboptimal quality of the samples received in our laboratory in Madrid, we applied alternative schemes for their analysis. In the first scheme, we bypassed the standard approach of applying systematic mycobacterial interspersed repetitive units-variable number of tandem repeats (MIRU-VNTR) and used a strain-specific polymerase chain reaction (PCR) that allowed identifying a cluster involving six cases (C1). The second scheme followed the canonical MIRU-VNTR path coupled with a whole-genomic amplification step, by which a second unsuspected overlapping cluster (C2), was detected in the same prison. These findings justified the implementation of a surveillance programme adapted to local resources based on a tailored multiplex allele-specific oligonucleotide (ASO)-PCR targeting C1 and C2. Presence of the C2 strain at a different prison was determined. ASO-PCR was applied extensively and alerted to the active circulation of one of the strains within and beyond prisons. Our study shows that alternative methodological strategies may provide useful data in settings with lack of resources for performing systematic standard molecular epidemiology programmes and/or with suboptimal material for analysis.

Effect of mixed strain infections on clinical and epidemiological features of tuberculosis in Florida

Mixed infections with genetically distinct Mycobacterium tuberculosis (MTB) strains within a single host have been documented in different settings; however, this phenomenon is rarely considered in the management and care of new and relapse tuberculosis (T.B.) cases. This study aims to establish the epidemiological and clinical features of mixed infections among culture-confirmed T.B. patients enrolled in tuberculosis care at the Florida Department of Health (FDOH) and measure its association with T.B. mortality. We analyzed de-identified surveillance data of T.B. cases enrolled in T.B. care from April 2008 to January 2018. Mixed MTB infection was determined by the presence of more than one Copy Number Variant (CNV) in at least one locus, based on the genotype profile pattern of at least one isolate using 24-locus Mycobacterial Interspersed Repetitive Unit-Variable Number Tandem Repeat (MIRU-VNTR). The prevalence of mixed MTB infections among the 4944 culture-confirmed TB cases included in this analysis was 2.6% (129). Increased odds of mixed infections were observed among middle-aged patients, 45-64 years (AOR = 2.38; 95% CI: 0.99, 5.69; p = 0.0513), older adults 65 years and above (AOR = 3.95; 95% CI: 1.63, 9.58; p = 0.0023) and patients with diabetes (OR = 1.77; 95% CI: 1.12, 2.80; p = 0.0150). There was no significant association between mixed infections and death. Our study provides insight into the epidemiological and clinical characteristics of patients with mixed MTB infections, which is essential in the management of T.B. patients.

Sources of Multidrug Resistance in Patients With Previous Isoniazid-Resistant Tuberculosis Identified Using Whole Genome Sequencing: A Longitudinal Cohort Study

BACKGROUND

Meta-analysis of patients with isoniazid-resistant tuberculosis (TB) given standard first-line anti-TB treatment indicated an increased risk of multidrug-resistant TB (MDR-TB) emerging (8%), compared to drug-sensitive TB (0.3%). Here we use whole genome sequencing (WGS) to investigate whether treatment of patients with preexisting isoniazid-resistant disease with first-line anti-TB therapy risks selecting for rifampicin resistance, and hence MDR-TB.

METHODS

Patients with isoniazid-resistant pulmonary TB were recruited and followed up for 24 months. Drug susceptibility testing was performed by microscopic observation drug susceptibility assay, mycobacterial growth indicator tube, and by WGS on isolates at first presentation and in the case of re-presentation. Where MDR-TB was diagnosed, WGS was used to determine the genomic relatedness between initial and subsequent isolates. De novo emergence of MDR-TB was assumed where the genomic distance was 5 or fewer single-nucleotide polymorphisms (SNPs), whereas reinfection with a different MDR-TB strain was assumed where the distance was 10 or more SNPs.

RESULTS

Two hundred thirty-nine patients with isoniazid-resistant pulmonary TB were recruited. Fourteen (14/239 [5.9%]) patients were diagnosed with a second episode of TB that was multidrug resistant. Six (6/239 [2.5%]) were identified as having evolved MDR-TB de novo and 6 as having been reinfected with a different strain. In 2 cases, the genomic distance was between 5 and 10 SNPs and therefore indeterminate.

CONCLUSIONS

In isoniazid-resistant TB, de novo emergence and reinfection of MDR-TB strains equally contributed to MDR development. Early diagnosis and optimal treatment of isoniazid-resistant TB are urgently needed to avert the de novo emergence of MDR-TB during treatment.

Molecular epidemiology of leprosy: An update

Molecular epidemiology investigations are notoriously challenging in the leprosy field mainly because the inherent characteristics of the disease as well as its yet uncultivated causative agents, Mycobacterium leprae and M. lepromatosis. Despite significant developments in understanding the biology of leprosy bacilli through genomic approaches, the exact mechanisms of transmission is still unclear and the factors underlying pathological variation of the disease in different patients remain as major gaps in our knowledge about leprosy. Despite these difficulties, the last two decades have seen the development of genotyping procedures based on PCR-sequencing of target loci as well as by the genome-wide analysis of an increasing number of geographically diverse isolates of leprosy bacilli. This has provided a foundation for molecular epidemiology studies that are bringing a better understanding of strain evolution associated with ancient human migrations, and phylogeographical insights about the spread of disease globally. This review discusses the advantages and drawbacks of the main tools available for molecular epidemiological investigations of leprosy and summarizes various methods ranging from PCR-based genotyping to genome-typing techniques. We also describe their main applications in analyzing the short-range and long-range transmission of the disease. Finally, we summarise the current gaps and challenges that remain in the field of molecular epidemiology of leprosy.

QuantTB - a method to classify mixed Mycobacterium tuberculosis infections within whole genome sequencing data

BACKGROUND

Mixed infections of Mycobacterium tuberculosis and antibiotic heteroresistance continue to complicate tuberculosis (TB) diagnosis and treatment. Detection of mixed infections has been limited to molecular genotyping techniques, which lack the sensitivity and resolution to accurately estimate the multiplicity of TB infections. In contrast, whole genome sequencing offers sensitive views of the genetic differences between strains of M. tuberculosis within a sample. Although metagenomic tools exist to classify strains in a metagenomic sample, most tools have been developed for more divergent species, and therefore cannot provide the sensitivity required to disentangle strains within closely related bacterial species such as M. tuberculosis. Here we present QuantTB, a method to identify and quantify individual M. tuberculosis strains in whole genome sequencing data. QuantTB uses SNP markers to determine the combination of strains that best explain the allelic variation observed in a sample. QuantTB outputs a list of identified strains, their corresponding relative abundances, and a list of drugs for which resistance-conferring mutations (or heteroresistance) have been predicted within the sample.

RESULTS

We show that QuantTB has a high degree of resolution and is capable of differentiating communities differing by less than 25 SNPs and identifying strains down to 1× coverage. Using simulated data, we found QuantTB outperformed other metagenomic strain identification tools at detecting strains and quantifying strain multiplicity. In a real-world scenario, using a dataset of 50 paired clinical isolates from a study of patients with either reinfections or relapses, we found that QuantTB could detect mixed infections and reinfections at rates concordant with a manually curated approach.

CONCLUSION

QuantTB can determine infection multiplicity, identify hetero-resistance patterns, enable differentiation between relapse and re-infection, and clarify transmission events across seemingly unrelated patients - even in low-coverage (1×) samples. QuantTB outperforms existing tools and promises to serve as a valuable resource for both clinicians and researchers working with clinical TB samples.

Diagnosis of osteoarticular tuberculosis via metagenomic next-generation sequencing: A case report

Osteoarticular tuberculosis (OAT) may cause severe complications and disability. Due to its indolent nature, OAT is difficult to diagnose in the early stages. Diagnosis by conventional culture is time-consuming and insensitive, and polymerase chain reaction-based molecular diagnostic methods are incapable of excluding co-infections. Metagenomic next-generation sequencing (mNGS) may identify a broad spectrum of microorganisms, including Mycobacterium, bacteria and fungi, in clinical specimens. Therefore, the diagnosis of OAT may be rapidly performed using mNGS. The present study reports on a case of OAT. The patient presented with right knee swelling and pain for 1 year; his C-reactive protein levels and erythrocyte sedimentation rate were markedly elevated. Although multiple pre-operative cultures were negative, mNGS was finally used to successfully detect the underlying pathogen. The result was confirmed by other molecular biology methods and Mycobacterium culture. Anti-tuberculosis therapy was administered accordingly and the patient finally recovered. In conclusion mNGS, with the ability to detect Mycobacterium and other microorganisms in a single assay, is an emerging approach for rapidly and accurately diagnosing OAT. This method may provide significant support to guide physicians in selecting the appropriate pharmacotherapy and surgical treatments.

Early Detection of Emergent Extensively Drug-Resistant Tuberculosis by Flow Cytometry-Based Phenotyping and Whole-Genome Sequencing

A critical gap in tuberculosis (TB) treatment is detection of emergent drug resistance. We hypothesized that advanced phenotyping with whole-genome sequencing (WGS) will detect low-frequency Mycobacterium tuberculosis drug resistance. We assessed a reporter mycobacteriophage (Φ²GFP10) in vitro to detect drug-resistant subpopulations and predict M. tuberculosis bactericidal activity in this pilot study. Subsequently, we prospectively studied 20 TB patients with serial Φ²GFP10, Xpert MTB/RIF, and M. tuberculosis culture through end of treatment. WGS was performed, and single nucleotide polymorphisms (SNPs) were examined to detect mixed infection in selected M. tuberculosis isolates. Resistant M. tuberculosis isolates were detected at 1:100,000, and changes in cytometry-gated events were predictive of in vitro M. tuberculosis bactericidal activity using the Φ²GFP10 assay. Emergent drug resistance was detected in one patient by Φ²GFP10 at 3 weeks but not by conventional testing (M. tuberculosis culture and GeneXpert). WGS revealed a phylogeographically distinct extensively drug-resistant tuberculosis (XDR-TB) genome, identical to an XDR-TB isolate from the patient's spouse. Variant lineage-specific SNPs were present early, suggesting mixed infection as the etiology of emergent resistance with temporal trends providing evidence for selection during treatment. Φ²GFP10 can detect low-frequency drug-resistant M. tuberculosis and with WGS characterize emergent M. tuberculosis resistance. In areas of high TB transmission and drug resistance, rapid screening for heteroresistance should be considered.

Mixed Mycobacterium tuberculosis-Strain Infections Are Associated With Poor Treatment Outcomes Among Patients With Newly Diagnosed Tuberculosis, Independent of Pretreatment Heteroresistance

Background

Heteroresistant Mycobacterium tuberculosis infections (defined as concomitant infection with drug-resistant and drug-susceptible strains) may explain the higher risk of poor tuberculosis treatment outcomes observed among patients with mixed-strain M. tuberculosis infections. We investigated the clinical effect of mixed-strain infections while controlling for pretreatment heteroresistance in a population-based sample of patients with tuberculosis starting first-line tuberculosis therapy in Botswana.

Methods

We performed 24-locus mycobacterial interspersed repetitive unit-variable number tandem-repeat analysis and targeted deep sequencing on baseline primary cultured isolates to detect mixed infections and heteroresistance, respectively. Drug-sensitive, micro-heteroresistant, macro-heteroresistant, and fixed-resistant infections were defined as infections in which the frequency of resistance was <0.1%, 0.1%-4%, 5%-94%, and ≥95%, respectively, in resistance-conferring domains of the inhA promoter, the katG gene, and the rpoB gene.

Results

Of the 260 patients with tuberculosis included in the study, 25 (9.6%) had mixed infections and 30 (11.5%) had poor treatment outcomes. Micro-heteroresistance, macro-heteroresistance, and fixed resistance were found among 11 (4.2%), 2 (0.8%), and 11 (4.2%), respectively, for isoniazid and 21 (8.1%), 0 (0%), and 10 (3.8%), respectively, for rifampicin. In multivariable analysis, mixed infections but not heteroresistant infections independently predicted poor treatment outcomes.

Conclusions

Among patients starting first-line tuberculosis therapy in Botswana, mixed infections were associated with poor tuberculosis treatment outcomes, independent of heteroresistance.

The human microbiota in pulmonary tuberculosis: Not so innocent bystanders

Mycobacterium tuberculosis (Mtb) infection is a worldwide health concern, which needs robust and efficient control strategies, and the evaluation of human microbiota can be very important in this regard. Dysbiosis of normal microbiota is an important issue in the pathogenesis of Mtb. However, only few studies demonstrated the interaction between Mtb infection and microbiota. The current study aimed at reviewing literature on gut and lung microbiota in Mtb infection. Eleven articles regarding gut and lung microbiota composition in individuals with Mtb infection were selected, and then the importance of gut-lung axis in Mtb infection was evaluated. Also the relationship between microbiota composition and Mtb infection were discussed in terms of treatment, epigenetic field, and biomarkers.

Exosomes in tuberculosis: Still terra incognita?

Today, diagnosis, vaccination, and treatment of tuberculosis (TB) remain major clinical challenges. Therefore, an introduction of new diagnostic measures and biomarkers is necessary to improve infection control. The ideal biomarker for TB infection can be defined as a host or pathogen-derived biomolecule, which is potent for identifying infection and determining its clinical stage. Exosomes, defined as cell-derived nanovesicles released into biological fluids, are involved in cell-cell communication and immune modulation. These vesicles have emerged as a new platform for improving the clinical diagnosis and prognosis of different infectious diseases and cancers. The role of these nanovehicles, as alternative biomarkers for the improvement of TB diagnosis and treatment, has been demonstrated in a significant body of literature. In this review, we summarized recent progress in the clinical application of exosome-based biomarkers in TB infection.

Molecular characterization and drug susceptibility profile of Mycobacterium tuberculosis isolates from Northeast Bangladesh

Tuberculosis (TB) remains a major public health problem worldwide including in Bangladesh. Molecular epidemiological tools provide genotyping profiles of Mycobacterium tuberculosis (M. tuberculosis) strains that can give insight into the transmission of TB in a specific region. The objective of the study was to identify the genetic diversity and drug susceptibility profile of M. tuberculosis strains circulating in the northeast Bangladesh. A total of 244 smear-positive sputum specimens were collected from two referral hospitals in Mymensingh and Netrakona districts. The isolated strains were genotyped by deletion analysis, spoligotyping, and MIRU-VNTR typing. We also analyzed the distributions of drug susceptibility pattern and demographic data among different genotypes. All isolates were identified as M. tuberculosis and among them 167 strains (68.44%) were 'ancestral' and the remaining 77 (31.56%) were 'modern' type. Spoligotyping analysis yielded 119 distinct patterns, among them, 86 isolates had unique patterns and the remaining 158 were grouped into 33 distinct clusters containing 2 to 18 isolates. The predominant spoligotypes belong to the EAI lineage strains, comprising 66 (27.04%) isolates followed by Beijing (7.38%), T1 (6.15%), CAS1-Delhi (5.33), LAM9 (3.28%), MANU-2 and X2. MIRU-VNTR analysis revealed 167 isolates (68%) had unique patterns, whereas 77 (32%) were grouped into 26 clusters and the rate of recent transmission was 20.9%, suggesting that the majority of TB cases in this region are caused by the reactivation of previous TB infections rather than recent transmission. About 136 (55.7%) isolates were sensitive to four anti-TB drugs, 69 (28.3%) were resistant to one or more (except rifampicin and isoniazid combination) drugs and 39 (15.9%) were MDR. In conclusion, our study provides a first insight into molecular characterization and drug resistance profile of M. tuberculosis strains in northeast Bangladesh which will ultimately contribute to the national TB control program.

Nano-biosensing approaches on tuberculosis: Defy of aptamers

Tuberculosis is a major global health problem caused by the bacterium Mycobacterium tuberculosis (Mtb) complex. According to WHO reports, 53 million TB patients died from 2000 to 2016. Therefore, early diagnosis of the disease is of great importance for global health care programs. The restrictions of traditional methods have encouraged the development of innovative methods for rapid, reliable, and cost-effective diagnosis of tuberculosis. In recent years, aptamer-based biosensors or aptasensors have drawn great attention to sensitive and accessible detection of tuberculosis. Aptamers are small short single-stranded molecules of DNA or RNA that fold to a unique form and bind to targets. Once combined with nanomaterials, nano-scale aptasensors provide powerful analytical platforms for diagnosing of tuberculosis. Various groups designed and studied aptamers specific for the whole cells of M. tuberculosis, mycobacterial proteins and IFN-γ for early diagnosis of TB. Advantages such as high specificity and strong affinity, potential for binding to a larger variety of targets, increased stability, lower costs of synthesis and storage requirements, and lower probability of contamination make aptasensors pivotal alternatives for future TB diagnostics. In recent years, the concept of SOMAmer has opened new horizons in high precision detection of tuberculosis biomarkers. This review article provides a description of the research progresses of aptamer-based and SOMAmer-based biosensors and nanobiosensors for the detection of tuberculosis.