Whole genome sequencing of Mycobacterium tuberculosis for detection of drug resistance: a systematic review

Whole-genome sequencing analysis of multidrug-resistant Mycobacterium tuberculosis from Java, Indonesia

Introduction. Multidrug-resistant tuberculosis (MDR-TB) is a major public health problem globally, including in Indonesia. Whole-genome sequencing (WGS) analysis has rarely been used for the study of TB and MDR-TB in Indonesia.Aim. We evaluated the use of WGS for drug-susceptibility testing (DST) and to investigate the population structure of drug-resistant Mycobacterium tuberculosis in Java, Indonesia.Methodology. Thirty suspected MDR-TB isolates were subjected to MGIT 960 system (MGIT)-based DST and to WGS. Phylogenetic analysis was done using the WGS data. Results obtained using MGIT-based DST and WGS-based DST were compared.Results. Agreement between WGS and MGIT was 93.33 % for rifampicin, 83.33 % for isoniazid and 76.67 % for streptomycin but only 63.33 % for ethambutol. Moderate WGS-MGIT agreement was found for second-line drugs including amikacin, kanamycin and fluoroquinolone (73.33-76.67 %). MDR-TB was more common in isolates of the East Asian Lineage (63.3%). No evidence of clonal transmission of DR-TB was found among members of the tested population.Conclusion. Our study demonstrated the applicability of WGS for DST and molecular epidemiology of DR-TB in Java, Indonesia. We found no transmission of DR-TB in Indonesia.

Citywide Transmission of Multidrug-resistant Tuberculosis Under China's Rapid Urbanization: A Retrospective Population-based Genomic Spatial Epidemiological Study

BACKGROUND

Population movement could extend multidrug-resistant tuberculosis (MDR-TB) transmission and complicate its global prevalence. We sought to identify the high-risk populations and geographic sites of MDR-TB transmission in Shenzhen, the most common destination for internal migrants in China.

METHODS

We performed a population-based, retrospective study in patients diagnosed with MDR-TB in Shenzhen during 2013-2017. By defining genomic clusters with a threshold of 12-single-nucleotide polymorphism distance based on whole-genome sequencing of their clinical strains, the clustering rate was calculated to evaluate the level of recent transmission. Risk factors were identified by multivariable logistic regression. To further delineate the epidemiological links, we invited the genomic-clustered patients to an in-depth social network investigation.

RESULTS

In total, 105 (25.2%) of the 417 enrolled patients with MDR-TB were grouped into 40 genome clusters, suggesting recent transmission of MDR strains. The adjusted risk for student to have a clustered strain was 4.05 (95% confidence interval, 1.06-17.0) times greater than other patients. The majority (70%, 28/40) of the genomic clusters involved patients who lived in different districts, with residences separated by an average of 8.76 kilometers. Other than household members, confirmed epidemiological links were also identified among classmates and workplace colleagues.

CONCLUSIONS

These findings demonstrate that local transmission of MDR-TB is a serious problem in Shenzhen. While most transmission occurred between people who lived distant from each other, there was clear evidence that transmission occurred in schools and workplaces, which should be included as targeted sites for active case finding.The average residential distance between genomic-clustered cases was more than 8 kilometers, while schools and workplaces, identified as sites of transmission in this study, deserve increased vigilance for targeted case finding of multidrug-resistant tuberculosis.

Tuberculosis in children: screening, diagnosis and management

PURPOSE OF REVIEW

The present review focuses on recent advances and current challenges in screening, diagnosis and management of tuberculosis (TB) in children, encompassing TB infection and TB disease, and public health priorities for screening and family engagement.

RECENT FINDINGS

Although awareness has improved in recent years that children in TB endemic areas suffer a huge disease burden, translation into better prevention and care remains challenging. Recent WHO guidelines have incorporated screening of all household contacts of pulmonary TB cases, but implementation in high incidence settings remains limited. Improved tests using noninvasive samples, such as the lateral flow urinary lipoarabinomannan assay and the new Xpert Ultra assay applied to induced sputum or stool in young children, are showing promise and further assessment is eagerly awaited. From a treatment perspective, child-friendly dispersible fixed dose combination tablets are now widely available with excellent acceptability and tolerance reported in young children.

SUMMARY

High-level government commitment to TB control as a public health priority and feasible strategies to achieve this are required to contain the global epidemic, whereas strong engagement of local TB clinics and affected families in TB prevention is essential to limit secondary cases and protect exposed children.

Detection of low-frequency resistance-mediating SNPs in next-generation sequencing data of Mycobacterium tuberculosis complex strains with binoSNP

Accurate drug resistance detection is key for guiding effective tuberculosis treatment. While genotypic resistance can be rapidly detected by molecular methods, their application is challenged by mixed mycobacterial populations comprising both susceptible and resistant cells (heteroresistance). For this, next-generation sequencing (NGS) based approaches promise the determination of variants even at low frequencies. However, accurate methods for a valid detection of low-frequency variants in NGS data are currently lacking. To tackle this problem, we developed the variant detection tool binoSNP which allows the determination of low-frequency single nucleotide polymorphisms (SNPs) in NGS datasets from Mycobacterium tuberculosis complex (MTBC) strains. By taking a reference-mapped file as input, binoSNP evaluates each genomic position of interest using a binomial test procedure. binoSNP was validated using in-silico, in-vitro, and serial patient isolates datasets comprising varying genomic coverage depths (100-500×) and SNP allele frequencies (1-30%). Overall, the detection limit for low-frequency SNPs depends on the combination of coverage depth and allele frequency of the resistance-associated mutation. binoSNP allows for valid detection of resistance associated SNPs at a 1% frequency with a coverage ≥400×. In conclusion, binoSNP provides a valid approach to detect low-frequency resistance-mediating SNPs in NGS data from clinical MTBC strains. It can be implemented in automated, end-user friendly analysis tools for NGS data and is a step forward towards individualized TB therapy.

[Molecular diagnosis of tuberculosis]

Tuberculosis is caused by the M. tuberculosis complex. Its slow growth delays the bacteriological diagnosis based on phenotypic tests. Molecular biology has significantly reduced this delay, notably thanks to the deployment of the Xpert® MTB/RIF test (Cepheid), which detects the M. tuberculosis complex and rifampicin resistance in 2hours. Other tests detecting isoniazid and second-line antituberculous drugs resistance have been developed. However, the performances of molecular tests are significantly reduced if the acid-fast bacilli microscopy screening is negative. It is therefore crucial to limit their indication to strong clinical suspicions. Resistance detection tests only explore certain characterized positions; however, not all drug-resistance mutations are known. Moreover, the performances vary for different antituberculous drugs. The advent of genomic sequencing is promising. Its integration into routine workflow still needs to be evaluated and the data analysis remains to be standardized. The rise of molecular biology techniques has revolutionized the diagnosis of tuberculosis and drug resistance. However, they remain screening tests; results still have to be confirmed by phenotypic reference methods.

Molecular characterisation of multidrug-resistant Mycobacterium tuberculosis isolates from a high-burden tuberculosis state in Brazil

Tuberculosis (TB) is the leading cause of death among infectious diseases worldwide. Among the estimated cases of drug-resistant TB, approximately 60% occur in the BRICS countries (Brazil, Russia, India, China and South Africa). Among Brazilian states, primary and acquired multidrug-resistant TB (MDR-TB) rates were the highest in Rio Grande do Sul (RS). This study aimed to perform molecular characterisation of MDR-TB in the State of RS, a high-burden Brazilian state. We performed molecular characterisation of MDR-TB cases in RS, defined by drug susceptibility testing, using 131 Mycobacterium tuberculosis (M.tb) DNA samples from the Central Laboratory. We carried out MIRU-VNTR 24loci, spoligotyping, sequencing of the katG, inhA and rpoB genes and RD^Rio sublineage identification. The most frequent families found were LAM (65.6%) and Haarlem (22.1%). RD^Rio deletion was observed in 42 (32%) of the M.tb isolates. Among MDR-TB cases, eight (6.1%) did not present mutations in the studied genes. In 116 (88.5%) M.tb isolates, we found mutations associated with rifampicin (RIF) resistance in rpoB gene, and in 112 isolates (85.5%), we observed mutations related to isoniazid resistance in katG and inhA genes. An insertion of 12 nucleotides (CCAGAACAACCC) at the 516 codon in the rpoB gene, possibly responsible for a decreased interaction of RIF and RNA polymerase, was found in 19/131 of the isolates, belonging mostly to LAM and Haarlem families. These results enable a better understanding of the dynamics of transmission and evolution of MDR-TB in the region.

Urinary tuberculosis: still a challenge

BACKGROUND

Urinary tuberculosis (TB) is a challenging disease to cope with, as there has been no noticeable difference in basic diagnostic and therapeutic options in clinical practice over time.

PURPOSE

The aim of the current review was the critical assessment and evaluation of TB, which remains a major global health problem.

METHODS

The available literature regarding TB in the PubMed database was extensively searched.

RESULTS

New interdisciplinary team approaches such as next-generation sequencing are promising for the diagnosis and treatment of the disease. The epidemiology of the disease is changing with globalization and increasing migration events; however, the knowledge here is limited. Despite ongoing destruction, kidney functions need to be preserved as much as possible, and relatively rapid development of minimally invasive techniques relieved the surgeons in this regard. Experience is increasing in minimally invasive techniques that provide better comfort for patients compared to extensive radical surgeries.

CONCLUSIONS

Knowing the pathogenesis of urinary TB is essential for understanding the range of clinical manifestations. The onset of the disease is usually insidious. Despite modern TB drugs, reconstructive surgery, and minimally invasive procedures, progression cannot be prevented in some patients, and patient selection is essential, but we still do not have sufficient information and objective parameters to predict progression.

Using a Heat Diffusion Model to Detect Potential Drug Resistance Genes of Mycobacterium tuberculosis

BACKGROUND

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), is one of the oldest known and most dangerous diseases. Although the spread of TB was controlled in the early 20th century using antibiotics and vaccines, TB has again become a threat because of increased drug resistance. There is still a lack of effective treatment regimens for a person who is already infected with multidrug-resistant Mtb (MDR-Mtb) or extensively drug-resistant Mtb (XDRMtb). In the past decades, many research groups have explored the drug resistance profiles of Mtb based on sequence data by GWAS, which identified some mutations that were significantly linked with drug resistance, and attempted to explain the resistance mechanisms. However, they mainly focused on several significant mutations in drug targets (e.g. rpoB, katG). Some genes which are potentially associated with drug resistance may be overlooked by the GWAS analysis.

OBJECTIVE

In this article, our motivation is to detect potential drug resistance genes of Mtb using a heat diffusion model.

METHODS

All sequencing data, which contained 127 samples of Mtb, i.e. 34 ethambutol-, 65 isoniazid-, 53 rifampicin- and 45 streptomycin-resistant strains. The raw sequence data were preprocessed using Trimmomatic software and aligned to the Mtb H37Rv reference genome using Bowtie2. From the resulting alignments, SAMtools and VarScan were used to filter sequences and call SNPs. The GWAS was performed by the PLINK package to obtain the significant SNPs, which were mapped to genes. The P-values of genes calculated by GWAS were transferred into a heat vector. The heat vector and the Mtb protein-protein interactions (PPI) derived from the STRING database were inputted into the heat diffusion model to obtain significant subnetworks by HotNet2. Finally, the most significant (P < 0.05) subnetworks associated with different phenotypes were obtained. To verify the change of binding energy between the drug and target before and after mutation, the method of molecular dynamics simulation was performed using the AMBER software.

RESULTS

We identified significant subnetworks in rifampicin-resistant samples. Excitingly, we found rpoB and rpoC, which are drug targets of rifampicin. From the protein structure of rpoB, the mutation location was extremely close to the drug binding site, with a distance of only 3.97 Å. Molecular dynamics simulation revealed that the binding energy of rpoB and rifampicin decreased after D435V mutation. To a large extent, this mutation can influence the affinity of drug-target binding. In addition, topA and pyrG were reported to be linked with drug resistance, and might be new TB drug targets. Other genes that have not yet been reported are worth further study.

CONCLUSION

Using a heat diffusion model in combination with GWAS results and protein-protein interactions, the significantly mutated subnetworks in rifampicin-resistant samples were found. The subnetwork not only contained the known targets of rifampicin (rpoB, rpoC), but also included topA and pyrG, which are potentially associated with drug resistance. Together, these results offer deeper insights into drug resistance of Mtb, and provides potential drug targets for finding new antituberculosis drugs.

Whole genome sequencing of Mycobacterium tuberculosis isolates and clinical outcomes of patients treated for multidrug-resistant tuberculosis in Tanzania

BACKGROUND

Tuberculosis (TB), particularly multi- and or extensive drug resistant TB, is still a global medical emergency. Whole genome sequencing (WGS) is a current alternative to the WHO-approved probe-based methods for TB diagnosis and detection of drug resistance, genetic diversity and transmission dynamics of Mycobacterium tuberculosis complex (MTBC). This study compared WGS and clinical data in participants with TB.

RESULTS

This cohort study performed WGS on 87 from MTBC DNA isolates, 57 (66%) and 30 (34%) patients with drug resistant and susceptible TB, respectively. Drug resistance was determined by Xpert® MTB/RIF assay and phenotypic culture-based drug-susceptibility-testing (DST). WGS and bioinformatics data that predict phenotypic resistance to anti-TB drugs were compared with participant's clinical outcomes. They were 47 female participants (54%) and the median age was 35 years (IQR): 29-44). Twenty (23%) and 26 (30%) of participants had TB/HIV co-infection BMI < 18 kg/m2 respectively. MDR-TB participants had MTBC with multiple mutant genes, compared to those with mono or polyresistant TB, and the majority belonged to lineage 3 Central Asian Strain (CAS). Also, MDR-TB was associated with delayed culture-conversion (median: IQR (83: 60-180 vs. 51:30-66) days). WGS had high concordance with both culture-based DST and Xpert® MTB/RIF assay in detecting drug resistance (kappa = 1.00).

CONCLUSION

This study offers comparison of mutations detected by Xpert and WGS with phenotypic DST of M. tuberculosis isolates in Tanzania. The high concordance between the different methods and further insights provided by WGS such as PZA-DST, which is not routinely performed in most resource-limited-settings, provides an avenue for inclusion of WGS into diagnostic matrix of TB including drug-resistant TB.

Pathogen Genomics in Public Health

Rapid advances in DNA sequencing technology ("next-generation sequencing") have inspired optimism about the potential of human genomics for "precision medicine." Meanwhile, pathogen genomics is already delivering "precision public health" through more effective investigations of outbreaks of foodborne illnesses, better-targeted tuberculosis control, and more timely and granular influenza surveillance to inform the selection of vaccine strains. In this article, we describe how public health agencies have been adopting pathogen genomics to improve their effectiveness in almost all domains of infectious disease. This momentum is likely to continue, given the ongoing development in sequencing and sequencing-related technologies.

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.

Whole genome sequencing, analyses of drug resistance-conferring mutations, and correlation with transmission of Mycobacterium tuberculosis carrying katG-S315T in Hanoi, Vietnam

Drug-resistant tuberculosis (TB) is a serious global problem, and pathogen factors involved in the transmission of isoniazid (INH)-resistant TB have not been fully investigated. We performed whole genome sequencing of 332 clinical Mycobacterium tuberculosis (Mtb) isolates collected from patients newly diagnosed with smear-positive pulmonary TB in Hanoi, Vietnam. Using a bacterial genome-wide approach based on linear mixed models, we investigated the associations between 31-bp k-mers and clustered strains harboring katG-S315T, a major INH-resistance mutation in the present cohort and in the second panel previously published in South Africa. Five statistically significant genes, namely, PPE18/19, gid, emrB, Rv1588c, and pncA, were shared by the two panels. We further identified variants of the genes responsible for these k-mers, which are relevant to the spread of INH-resistant strains. Phylogenetic convergence test showed that variants relevant to PPE46/47-like chimeric genes were significantly associated with the same phenotype in Hanoi. The associations were further confirmed after adjustment for the confounders. These findings suggest that genomic variations of the pathogen facilitate the expansion of INH-resistance TB, at least in part, and our study provides a new insight into the mechanisms by which drug-resistant Mtb maintains fitness and spreads in Asia and Africa.

From genotype to antibiotic susceptibility phenotype in the order Enterobacterales: a clinical perspective

OBJECTIVES

Predicting the antibiotic susceptibility phenotype from genomic data is challenging, especially for some specific antibiotics in the order Enterobacterales. Here we aimed to assess the performance of whole genomic sequencing (WGS) for predicting the antibiotic susceptibility in various Enterobacterales species using the detection of antibiotic resistance genes (ARGs), specific mutations and a knowledge-based decision algorithm.

METHODS

We sequenced (Illumina MiSeq, 2×250 bp) 187 clinical isolates from species possessing (n = 98) or not (n = 89) an intrinsic AmpC-type cephalosporinase. Phenotypic antibiotic susceptibility was performed by the disc diffusion method. Reads were assembled by A5-miseq and ARGs were identified from the ResFinder database using Diamond. Mutations on GyrA and ParC topoisomerases were studied. Piperacillin, piperacillin-tazobactam, ceftazidime, cefepime, meropenem, amikacin, gentamicin and ciprofloxacin were considered for prediction.

RESULTS

A total of 1496 isolate/antibiotic combinations (187 isolates × 8 antibiotics) were considered. In 230 cases (15.4%), no attempt of prediction was made because it could not be supported by current knowledge. Among the 1266 attempts, 1220 (96.4%) were correct (963 for predicting susceptibility and 257 for predicting resistance), 24 (1.9%) were major errors (MEs) and 22 (1.7%) were very major errors (VMEs). Concordance were similar between non-AmpC and AmpC-producing Enterobacterales (754/784 (96.2%) vs 466/482 (96.7%), chi-square test p 0.15), but more VMEs were observed in non-AmpC producing strains than in those producing an AmpC (19/784 (2.4%) vs 3/466 (0.6%), chi-square test p 0.02). The majority of VMEs were putatively due to the overexpression of chromosomal genes.

CONCLUSIONS

In conclusion, the inference of antibiotic susceptibility from genomic data showed good performances for non-AmpC and AmpC-producing Enterobacterales species. However, more knowledge about the mechanisms underlying the derepression of AmpC are needed.

Fluoroquinolone heteroresistance in Mycobacterium tuberculosis: detection by genotypic and phenotypic assays in experimentally mixed populations

Heteroresistance - the simultaneous presence of drug-susceptible and -resistant organisms - is common in Mycobacterium tuberculosis. In this study, we aimed to determine the limit of detection (LOD) of genotypic assays to detect gatifloxacin-resistant mutants in experimentally mixed populations. A fluoroquinolone-susceptible M. tuberculosis mother strain (S) and its in vitro selected resistant daughter strain harbouring the D94G mutation in gyrA (R) were mixed at different ratio’s. Minimum inhibitory concentrations (MICs) against gatifloxacin were determined, while PCR-based techniques included: line probe assays (Genotype MTBDRsl and GenoScholar-FQ + KM TB II), Sanger sequencing and targeted deep sequencing. Droplet digital PCR was used as molecular reference method. A breakpoint concentration of 0.25 mg/L allows the phenotypic detection of ≥1% resistant bacilli, whereas at 0.5 mg/L ≥ 5% resistant bacilli are detected. Line probe assays detected ≥5% mutants. Sanger sequencing required the presence of around 15% mutant bacilli to be detected as (hetero) resistant, while targeted deep sequencing detected ≤1% mutants. Deep sequencing and phenotypic testing are the most sensitive methods for detection of fluoroquinolone-resistant minority populations, followed by line probe assays (provided that the mutation is confirmed by a mutation band), while Sanger sequencing proved to be the least sensitive method.

Deciphering drug resistance in Mycobacterium tuberculosis using whole-genome sequencing: progress, promise, and challenges

Tuberculosis (TB) is a global infectious threat that is intensified by an increasing incidence of highly drug-resistant disease. Whole-genome sequencing (WGS) studies of Mycobacterium tuberculosis, the causative agent of TB, have greatly increased our understanding of this pathogen. Since the first M. tuberculosis genome was published in 1998, WGS has provided a more complete account of the genomic features that cause resistance in populations of M. tuberculosis, has helped to fill gaps in our knowledge of how both classical and new antitubercular drugs work, and has identified specific mutations that allow M. tuberculosis to escape the effects of these drugs. WGS studies have also revealed how resistance evolves both within an individual patient and within patient populations, including the important roles of de novo acquisition of resistance and clonal spread. These findings have informed decisions about which drug-resistance mutations should be included on extended diagnostic panels. From its origins as a basic science technique, WGS of M. tuberculosis is becoming part of the modern clinical microbiology laboratory, promising rapid and improved detection of drug resistance, and detailed and real-time epidemiology of TB outbreaks. We review the successes and highlight the challenges that remain in applying WGS to improve the control of drug-resistant TB through monitoring its evolution and spread, and to inform more rapid and effective diagnostic and therapeutic strategies.

Personalized Approach as a Basis for the Future Diagnosis of Tuberculosis (Literature Review)

The global spread of tuberculosis remains one of actual problems of public health despite of introduction of public health safety programs. Early, rapid and accurate identification of M. tuberculosis and determination of drug susceptibility are essential for treatment and management of this disease. Delay in delivering results prolongs potentially inappropriate antituberculosis therapy, contributing to emergence of drug resistance, reducing treatment options and increasing treatment duration and associated costs, resulting in increased mortality and morbidity. Faster, more comprehensive diagnostics will enable earlier use of the most appropriate drug regimen, thus improving patient outcomes and reducing overall healthcare costs. The treatment of infection based on the using of massive antimicrobial therapy with analysis of bacterial strains resistance to first line drugs (FLD) isoniazid (INH), rifampin (RIF), pyrazinamide (PZA), ethambutol (EMB) and streptomycin (SM). However, the public health practitioners pay no attention to functional activity of human immune system genes. The interaction of bacterial genomes and immune system genes plays the major role in infection progress. There is growing evidence that, together with human and environmental factors, Mycobacterium tuberculosis complex strain diversity contributes to the variable outcome of infection and disease in human TB. We suppose that the future of diagnosis and treatment of tuberculosis lies in the field of personal medicine with comprehensive analysis of host and pathogen genes.

Whole genomic sequencing as a tool for diagnosis of drug and multidrug-resistance tuberculosis in an endemic region in Mexico

Background

Whole genome sequencing (WGS) has been proposed as a tool for diagnosing drug resistance in tuberculosis. However, reports of its effectiveness in endemic countries with important numbers of drug resistance are scarce. The goal of this study was to evaluate the effectiveness of this procedure in isolates from a tuberculosis endemic region in Mexico.

Methods

WGS analysis was performed in 81 tuberculosis positive clinical isolates with a known phenotypic profile of resistance against first-line drugs (isoniazid, rifampin, ethambutol, pyrazinamide and streptomycin). Mutations related to drug resistance were identified for each isolate; drug resistant genotypes were predicted and compared with the phenotypic profile. Genotypes and transmission clusters based on genetic distances were also characterized.

Findings

Prediction by WGS analysis of resistance against isoniazid, rifampicin, ethambutol, pyrazinamide and streptomycin showed sensitivity values of 84%, 96%, 71%, 75% and 29%, while specificity values were 100%, 94%, 90%, 90% and 98%, respectively. Prediction of multidrug resistance showed a sensitivity of 89% and specificity of 97%. Moreover, WGS analysis revealed polymorphisms related to second-line drug resistance, enabling classification of eight and two clinical isolates as pre- and extreme drug-resistant cases, respectively. Lastly, four lineages were identified in the population (L1, L2, L3 and L4). The most frequent of these was L4, which included 90% (77) of the isolates. Six transmission clusters were identified; the most frequent was TC6, which included 13 isolates with a L4.1.1 and a predominantly multidrug-resistant condition.

Conclusions

The results illustrate the utility of WGS for establishing the potential for prediction of resistance against first and second line drugs in isolates of tuberculosis from the region. They also demonstrate the feasibility of this procedure for use as a tool to support the epidemiological surveillance of drug- and multidrug-resistant tuberculosis.

Comparisons of whole-genome sequencing and phenotypic drug susceptibility testing for Mycobacterium tuberculosis causing MDR-TB and XDR-TB in Thailand

Drug-resistant tuberculosis (TB) is a major public health problem. There is little information regarding the genotypic-phenotypic association of anti-TB drugs, especially for second-line drugs. This study compared phenotypic drug susceptibility testing (DST) with predictions based on whole-genome sequencing (WGS) data for 266 Mycobacterium tuberculosis isolates. Phenotypic DST used the standard proportional method. Clinical isolates of M. tuberculosis collected in Thailand between 1998 and 2013 comprised 51 drug-sensitive strains, six mono-resistant strains, two multiple-resistant strains, 88 multi-drug-resistant strains, 95 pre-extensively drug-resistant strains and 24 extensively drug-resistant strains. WGS analysis was performed using the computer programs PhyResSE and TB-Profiler. TB-Profiler had higher average concordance with phenotypic DST than PhyResSE for both first-line (91.96% vs. 91.4%) and second-line (79.67% vs. 78.20%) anti-TB drugs. The average sensitivity for all anti-TB drugs was also higher (83.13% vs. 72.08%) with slightly lower specificity (83.50% vs. 86.68%). Regardless of the program used, isoniazid, rifampicin and amikacin had the highest concordance with phenotypic DST (96.2%, 93.5% and 95.6%, respectively). Ethambutol, ethionamide and fluoroquinolones had the lowest concordance (87.34%, 81.44% and 73.85%, respectively). Concordance rates of ofloxacin (a second-generation fluoroquinolone), levofloxacin, moxifloxacin and gatifloxacin (third- and fourth-generation fluoroquinolones) were 91.79%, 76.62%, 72.64% and 57.35%, respectively. Discordance between phenotypic and WGS-based DSTs may be due, in part, to the choice of critical concentration and variable reproducibility of the phenotypic tests. It may also be due to limitations of the mutation databases (especially for the second-line drugs) and the analysis program used. Mutations related to fluoroquinolone resistance, especially the later generations, need to be identified.

Molecular and genomic typing for tuberculosis surveillance: A survey study in 26 European countries

BACKGROUND

Molecular typing and whole genome sequencing (WGS) information is used for (inter-) national outbreak investigations. To assist the implementation of these techniques for tuberculosis (TB) surveillance and outbreak investigations at European level there is a need for inter-country collaboration and standardization. This demands more information on molecular typing practices and capabilities of individual countries. We aimed to review the use of molecular/genomic typing for TB surveillance in European Union and European Economic Area countries in 2016; assess its public health value; and collect experiences on typing data use for cross-border cluster investigations.

METHOD

A web-based questionnaire was provided to all TB National Focal Points. The questionnaire consisted of three parts: i) Use and integration of molecular and genomic typing data into TB surveillance; ii) Cross-border cluster investigation and international collaboration, and iii) Perception and evaluation of public health benefits of molecular and genomic typing for TB surveillance.

RESULTS

Of 26 responding countries, 20 used molecular typing for TB surveillance, including nine applying WGS. The level of integration into the national surveillance was heterogeneous. Among six countries not using typing for TB surveillance, more than half planned its implementation soon. Overall, most countries perceived an added public health value of molecular typing for TB control. Concerning international cluster investigations, countries had little experience and did not have standard protocols to exchange typing data.

CONCLUSION

Our study shows a wide use of molecular and genomic typing data for TB surveillance in EU/EEA countries and reveals that transition to WGS-based typing is ongoing or is considered in most countries. However, our results also show a high heterogeneity in the use and integration of typing data for TB surveillance. Standardization of typing data use for TB surveillance is needed and formal procedures should be developed to facilitate international collaboration.

Whole-Genome Sequencing of Drug-Resistant Mycobacterium tuberculosis Strains, Tunisia, 2012-2016

To investigate transmission of drug-resistant strains of Mycobacterium tuberculosis in Tunisia, we performed whole-genome sequencing on 46 multidrug-resistant strains isolated during 2012-2016. Core-genome multilocus sequence typing grouped 30 strains (65.2%) into 3 clusters, indicating extensive recent transmission and Haarlem clone predominance. Whole-genome sequencing might help public health services undertake appropriate control actions.

Application of next-generation sequencing to detect variants of drug-resistant Mycobacterium tuberculosis: genotype-phenotype correlation

BACKGROUND

Drug resistance in Mycobacterium tuberculosis (MTB) is a major health issue worldwide. Recently, next-generation sequencing (NGS) technology has begun to be used to detect resistance genes of MTB. We aimed to assess the clinical usefulness of Ion S5 NGS TB research panel for detecting MTB resistance in Korean tuberculosis patients.

METHODS

Mycobacterium tuberculosis with various drug resistance profiles including susceptible strains (N = 36) were isolated from clinical specimens. Nucleic acids were extracted from inactivated culture medium and underwent amplicon-based NGS to detect resistance variants in eight genes (gyrA, rpoB, pncA, katG, eis, rpsL, embB, and inhA). Data from previous studies using the same panel were merged to yield pooled sensitivity and specificity values for detecting drug resistance compared to phenotype-based methods.

RESULTS

The sequencing reactions were successful for all samples. A total of 24 variants were considered to be related to resistance, and 6 of them were novel. Agreement between the phenotypic and genotypic results was excellent for isoniazid, rifampicin, and ethambutol, and was poor for streptomycin, amikacin, and kanamycin. The negative predictive values were greater than 97% for all drug classes, while the positive predictive values varied (44% to 100%). There was a possibility that common mutations could not be detected owing to the low coverage.

CONCLUSIONS

We successfully applied NGS for genetic analysis of drug resistances in MTB, as well as for susceptible strains. We obtained lists of polymorphisms and possible polymorphisms, which could be used as a guide for future tests applying NGS in mycobacteriology laboratories. When analyzing the results of NGS, coverage analysis of each samples for each gene and benign polymorphisms not related to drug resistance should be considered.

Genetic Diversity of Multi- and Extensively Drug-Resistant Mycobacterium tuberculosis Isolates in the Capital of Iran, Revealed by Whole-Genome Sequencing

The emergence and spread of multidrug resistant (MDR) Mycobacterium tuberculosis complex (MTBC) strains is a critical global health problem. Between 2014 and 2018, 606 MTBC strains were isolated from 13,892 suspected pulmonary tuberculosis (TB) patients in Tehran, Iran, including 16 (2.6%) MDR-TB cases. A combination of phenotypic and genotypic methods (whole-genome sequencing) was employed for the identification of additional drug resistances and strain-to-strain genetic distances as a marker for recent transmission events. MDR and extensively drug-resistant (XDR) TB cases were almost exclusively infected by lineage 2/Beijing strains (14/16, P < 0.001). We further showed that recent transmission and/or recent introduction of lineage 2/Beijing strains contribute to high XDR-TB rates among all MDR-TB cases and should be considered an emerging threat for TB control in Tehran. In addition, the extensive pre-existing drug resistance profiles of MDR/XDR strains will further challenge TB diagnostics in the region.

Advances in the molecular diagnosis of tuberculosis: From probes to genomes

Tuberculosis, disease caused by Mycobacterium tuberculosis, is currently the leading cause of death by a single infectious agent worldwide. Early, rapid and accurate identification of M. tuberculosis and the determination of drug susceptibility is essential for the treatment and management of this disease. Tuberculosis diagnosis is mainly based on chest radiography, smear microscopy and bacteriological culture. Smear microscopy has variable sensitivity, mainly in patients co-infected with the human immunodeficiency virus (HIV). Conventional culture for M. tuberculosis isolation, identification and drug susceptibility testing requires several weeks owning to the slow growth of M. tuberculosis. The delay in the time to results drives the prolongation of potentially inappropriate antituberculosis therapy contributing to the emergence of drug resistance, reducing treatment options and increasing treatment duration and associated costs, resulting in increased mortality and morbidity. For these reasons, novel diagnostic methods are need for timely identification of M. tuberculosis and determination of the antibiotic susceptibility profile of the infecting strain. Molecular methods offer enhanced sensitivity and specificity, early detection and the capacity to detect mixed infections. These technologies have improved turnaround time, cost effectiveness and are amenable for point-of-care testing. However, although these methods produce results within hours from sample collection, the phenotypic susceptibility testing is still needed for the determination of drug susceptibility and quantify the susceptibility levels of a given strain towards individual antibiotics. This review presents the history, advances and forthcoming promises in the molecular diagnosis of tuberculosis. An overview on the general principles, diagnostic value and the main advantages and disadvantages of the molecular methods used for the detection and identification of M. tuberculosis and its associated disease, is provided. It will be also discussed how the current phenotypic methods should be used in combination with the genotypic methods for rapid antituberculosis susceptibility testing.

Evaluation of whole genome sequencing and software tools for drug susceptibility testing of Mycobacterium tuberculosis

OBJECTIVES

Culture-based assays are currently the reference standard for drug susceptibility testing for Mycobacterium tuberculosis. They provide good sensitivity and specificity but are time consuming. The objective of this study was to evaluate whether whole genome sequencing (WGS), combined with software tools for data analysis, can replace routine culture-based assays for drug susceptibility testing of M. tuberculosis.

METHODS

M. tuberculosis cultures sent to the Finnish mycobacterial reference laboratory in 2014 (n = 211) were phenotypically tested by Mycobacteria Growth Indicator Tube (MGIT) for first-line drug susceptibilities. WGS was performed for all isolates using the Illumina MiSeq system, and data were analysed using five software tools (PhyResSE, Mykrobe Predictor, TB Profiler, TGS-TB and KvarQ). Diagnostic time and reagent costs were estimated for both methods.

RESULTS

The sensitivity of the five software tools to predict any resistance among strains was almost identical, ranging from 74% to 80%, and specificity was more than 95% for all software tools except for TGS-TB. The sensitivity and specificity to predict resistance to individual drugs varied considerably among the software tools. Reagent costs for MGIT and WGS were €26 and €143 per isolate respectively. Turnaround time for MGIT was 19 days (range 10-50 days) for first-line drugs, and turnaround time for WGS was estimated to be 5 days (range 3-7 days).

CONCLUSIONS

WGS could be used as a prescreening assay for drug susceptibility testing with confirmation of resistant strains by MGIT. The functionality and ease of use of the software tools need to be improved.

Dissecting whole-genome sequencing-based online tools for predicting resistance in Mycobacterium tuberculosis: can we use them for clinical decision guidance?

Whole-genome sequencing (WGS)-based bioinformatics platforms for the rapid prediction of resistance will soon be implemented in the Tuberculosis (TB) laboratory, but their accuracy assessment still needs to be strengthened. Here, we fully-sequenced a total of 54 multidrug-resistant (MDR) and five susceptible TB strains and performed, for the first time, a simultaneous evaluation of the major four free online platforms (TB Profiler, PhyResSE, Mykrobe Predictor and TGS-TB). Overall, the sensitivity of resistance prediction ranged from 84.3% using Mykrobe predictor to 95.2% using TB profiler, while specificity was higher and homogeneous among platforms. TB profiler revealed the best performance robustness (sensitivity, specificity, PPV and NPV above 95%), followed by TGS-TB (all parameters above 90%). We also observed a few discrepancies between phenotype and genotype, where, in some cases, it was possible to pin-point some "candidate" mutations (e.g., in the rpsL promoter region) highlighting the need for their confirmation through mutagenesis assays and potential review of the anti-TB genetic databases. The rampant development of the bioinformatics algorithms and the tremendously reduced time-frame until the clinician may decide for a definitive and most effective treatment will certainly trigger the technological transition where WGS-based bioinformatics platforms could replace phenotypic drug susceptibility testing for TB.

Drug-Resistant tuberculosis - primary transmission and management

The DOTS strategy assisted global tuberculosis (TB) control, but was unable to prevent the emergence and spread of drug-resistant strains. Genomic evidence confirms the transmission of drug-resistant Mycobacterium tuberculosis strains in many different settings, indicative of epidemic spread. These findings emphasise the need for enhanced infection control measures in health care and congregate settings. Young children in TB endemic areas are particularly vulnerable. Although advances in TB drug and vaccine development are urgently needed, improved access to currently available preventive therapy and treatment for drug resistant TB could reduce the disease burden and adverse outcomes experienced by children. We review new insights into the transmission dynamics of drug resistant TB, the estimated disease burden in children and optimal management strategies to consider.

Mycobacterium tuberculosis and whole-genome sequencing: how close are we to unleashing its full potential?

BACKGROUND

Nearly two decades after completion of the genome sequence of Mycobacterium tuberculosis (MTB), and with the advent of next generation sequencing technologies (NGS), whole-genome sequencing (WGS) has been applied to a wide range of clinical scenarios. Starting in 2017, England is the first country in the world to pioneer its use on a national scale for the diagnosis of tuberculosis, detection of drug resistance, and typing of MTB.

AIMS

This narrative review critically analyses the current applications of WGS for MTB and explains how close we are to realizing its full potential as a diagnostic, epidemiologic, and research tool.

SOURCES

We searched for reports (both original articles and reviews) published in English up to 31 May 2017, with combinations of the following keywords: whole-genome sequencing, Mycobacterium, and tuberculosis. MEDLINE, Embase, and Scopus were used as search engines. We included articles that covered different aspects of whole-genome sequencing in relation to MTB.

CONTENT

This review focuses on three main themes: the role of WGS for the prediction of drug susceptibility, MTB outbreak investigation and genetic diversity, and research applications of NGS.

IMPLICATIONS

Many of the original expectations have been accomplished, and we believe that with its unprecedented sensitivity and power, WGS has the potential to address many unanswered questions in the near future. However, caution is still needed when interpreting WGS data as there are some important limitations to be aware of, from correct interpretation of drug susceptibilities to the bioinformatic support needed.

Insight of Genus Corynebacterium: Ascertaining the Role of Pathogenic and Non-pathogenic Species

This review gathers recent information about genomic and transcriptomic studies in the Corynebacterium genus, exploring, for example, prediction of pathogenicity islands and stress response in different pathogenic and non-pathogenic species. In addition, is described several phylogeny studies to Corynebacterium, exploring since the identification of species until biological speciation in one species belonging to the genus Corynebacterium. Important concepts associated with virulence highlighting the role of Pld protein and Tox gene. The adhesion, characteristic of virulence factor, was described using the sortase mechanism that is associated to anchorage to the cell wall. In addition, survival inside the host cell and some diseases, were too addressed for pathogenic corynebacteria, while important biochemical pathways and biotechnological applications retain the focus of this review for non-pathogenic corynebacteria. Concluding, this review broadly explores characteristics in genus Corynebacterium showing to have strong relevance inside the medical, veterinary, and biotechnology field.

Rapid diagnosis of tuberculosis. Detection of drug resistance mechanisms

Tuberculosis is still a serious public health problem, with 10.8 million new cases and 1.8 million deaths worldwide in 2015. The diversity among members of the Mycobacterium tuberculosis complex, the causal agent of tuberculosis, is conducive to the design of different methods for rapid diagnosis. Mutations in the genes involved in resistance mechanisms enable the bacteria to elude the treatment. We have reviewed the methods for the rapid diagnosis of M. tuberculosis complex and the detection of susceptibility to drugs, both of which are necessary to prevent the onset of new resistance and to establish early, appropriate treatment.

The variability and reproducibility of whole genome sequencing technology for detecting resistance to anti-tuberculous drugs

BACKGROUND

The emergence of resistance to anti-tuberculosis drugs is a serious and growing threat to public health. Next-generation sequencing is rapidly gaining traction as a diagnostic tool for investigating drug resistance in Mycobacterium tuberculosis to aid treatment decisions. However, there are few little data regarding the precision of such sequencing for assigning resistance profiles.

METHODS

We investigated two sequencing platforms (Illumina MiSeq, Ion Torrent PGM™) and two rapid analytic pipelines (TBProfiler, Mykrobe predictor) using a well characterised reference strain (H37Rv) and clinical isolates from patients with tuberculosis resistant to up to 13 drugs. Results were compared to phenotypic drug susceptibility testing. To assess analytical robustness individual DNA samples were subjected to repeated sequencing.

RESULTS

The MiSeq and Ion PGM systems accurately predicted drug-resistance profiles and there was high reproducibility between biological and technical sample replicates. Estimated variant error rates were low (MiSeq 1 per 77 kbp, Ion PGM 1 per 41 kbp) and genomic coverage high (MiSeq 51-fold, Ion PGM 53-fold). MiSeq provided superior coverage in GC-rich regions, which translated into incremental detection of putative genotypic drug-specific resistance, including for resistance to para-aminosalicylic acid and pyrazinamide. The TBProfiler bioinformatics pipeline was concordant with reported phenotypic susceptibility for all drugs tested except pyrazinamide and para-aminosalicylic acid, with an overall concordance of 95.3%. When using the Mykrobe predictor concordance with phenotypic testing was 73.6%.

CONCLUSIONS

We have demonstrated high comparative reproducibility of two sequencing platforms, and high predictive ability of the TBProfiler mutation library and analytical pipeline, when profiling resistance to first- and second-line anti-tuberculosis drugs. However, platform-specific variability in coverage of some genome regions may have implications for predicting resistance to specific drugs. These findings may have implications for future clinical practice and thus deserve further scrutiny, set within larger studies and using updated mutation libraries.