SpolPred: rapid and accurate prediction of Mycobacterium tuberculosis spoligotypes from short genomic sequences

Delineating the evolutionary pathway to multidrug-resistant outbreaks of a Mycobacterium tuberculosis L4.1.2.1/Haarlem sublineage

OBJECTIVES

We sought to capture the evolutionary itinerary of the Mycobacterium tuberculosis L4.1.2.1/Haarlem sublineage in northern Tunisia, where it caused a major multidrug-resistant (MDR) tuberculosis outbreak in a context strictly negative for HIV infection.

METHODS

We combined whole genome sequencing and Bayesian approaches using a representative collection of drug-susceptible and drug-resistant L4.1.2.1/Haarlem clinical strains (n = 121) recovered from the outbreak region over 16 years.

RESULTS

In the absence of drug resistance, the L4.1.2.1/Haarlem sublineage showed a propensity for rapid transmission as witnessed by the high clustering (44.6%) and recent transmission rates (25%), as well as the reduced mean distance between genome pairs. The entire pool of L4.1.2.1/Haarlem MDR strains was found to be linked to either the aforementioned major outbreak (68 individuals, 2001-2016) or to a minor, newly uncovered outbreak (six cases, 2001-2011). Strikingly, the two outbreaks descended independently from a common ancestor that can be dated back to 1886.

CONCLUSIONS

Our data point to the intrinsic propensity for rapid transmission of the M. tuberculosis L4.1.2.1/Haarlem sublineage in northern Tunisia, linking the overall MDR tuberculosis epidemic to a single ancestor. These findings bring out the important role of the bacillus' genetic background in the emergence of successful MDR M. tuberculosis clones.

Spoligotyping of Mycobacterium tuberculosis - Comparing in vitro and in silico approaches

Spoligotyping is one of the molecular typing methods widely used for exploring the genetic variety of Mycobacterium tuberculosis. The aim of this study was to compare the spoligoprofiles of M. tuberculosis clinical isolates, obtained using in vitro and in silico approaches. The study included 230 M. tuberculosis isolates, recovered from Poland and Lithuania between 2018 and 2021. Spoligotyping in vitro was performed with a commercially available kit. Whole genome sequencing (WGS) was done with Illumina NovaSeq 6000 sequencer. Spoligotype International Types (SITs) were assigned according to the SITVIT2 database or using three different in silico tools, and based on WGS data, namely SpoTyping, SpolPred, and lorikeet. Upon in vitro spoligotyping, the isolates produced 65 different spoligotypes. Spoligotypes inferred from the WGS data were congruent with in vitro generated patterns in 81.7% (188/230) for lorikeet and 81.3% (187/230) for SpolPred and SpoTyping. Spacers 18 and 31 produced the highest ratio of discrepant results between in vitro and in silico approaches, with their signals discordantly assigned for 15 (6.5%) and 9 (3.9%) isolates, respectively. All three in silico approaches used were similarly efficient for M. tuberculosis spoligotype prediction. However, only SpoTyping could predict spoligotypes without a need for manual curation. Thus, we consider it as the most accurate tool. Its use is further advocated by the shortest time of analysis. A relatively high (ca. 20%) discordance between in vitro and in silico spoligotyping results was observed. While we discourage comparing conventional spoligotyping with in silico equivalents, we advise the use of the latter, as it improves the accuracy of spoligopatterns, and thus depicts the relatedness between the isolates more reliably.

simpiTB - a pipeline designed to extract meaningful information from whole genome sequencing data of Mycobacterium tuberculosis complex, allows to combine genomic, phylogenetic and clustering analyses in existing SITVIT databases

Data obtained from new sequencing technologies are evolving rapidly, leading to the development of specific bioinformatic tools, pipelines and softwares. Several algorithms and tools are today available allowing a better identification and description of Mycobacterium tuberculosis complex (MTBC) isolates worldwide. Our approach consists in applying existing methods to analyze DNA sequencing data (from FASTA or FASTQ files), and tentatively extract meaningful information that would facilitate identification as well as a better understanding and management of MTBC isolates (taking into account whole genome sequencing and classical genotyping data). The aim of this study is to propose a pipeline analysis allowing to potentially simplify MTBC data analysis by providing different ways to interpret genomic or genotyping information based on existing tools. Furthermore, we propose a "reconciledTB" list making a link with results directly obtained from whole genome sequencing (WGS) data and results obtained from classical genotyping analysis (data inferred from SpoTyping and MIRUReader). Data visualization graphics and trees generated provide additional elements to better understand and confer associations among information overlap analyses. Additionally, comparison between data entered in an international genotyping database (SITVITEXTEND) and ensuing data obtained from the pipeline not only provide meaningful information, but further suggest that simpiTB could also be suitable for new data integration in specific TB genotyping databases.

Comparison of in silico predicted Mycobacterium tuberculosis spoligotypes and lineages from whole genome sequencing data

Bacterial strain-types in the Mycobacterium tuberculosis complex underlie tuberculosis disease, and have been associated with drug resistance, transmissibility, virulence, and host-pathogen interactions. Spoligotyping was developed as a molecular genotyping technique used to determine strain-types, though recent advances in whole genome sequencing (WGS) technology have led to their characterization using SNP-based sub-lineage nomenclature. Notwithstanding, spoligotyping remains an important tool and there is a need to study the congruence between spoligotyping-based and SNP-based sub-lineage assignation. To achieve this, an in silico spoligotype prediction method ("Spolpred2") was developed and integrated into TB-Profiler. Lineage and spoligotype predictions were generated for > 28 k isolates and the overlap between strain-types was characterized. Major spoligotype families detected were Beijing (25.6%), T (18.6%), LAM (13.1%), CAS (9.4%), and EAI (8.3%), and these broadly followed known geographic distributions. Most spoligotypes were perfectly correlated with the main MTBC lineages (L1-L7, plus animal). Conversely, at lower levels of the sub-lineage system, the relationship breaks down, with only 65% of spoligotypes being perfectly associated with a sub-lineage at the second or subsequent levels of the hierarchy. Our work supports the use of spoligotyping (membrane or WGS-based) for low-resolution surveillance, and WGS or SNP-based systems for higher-resolution studies.

Genomic changes underpinning the emergence of a successful Mycobacterium tuberculosis Latin American and Mediterranean clonal complex

Introduction

The Latin American and Mediterranean sublineage (L4.3/LAM) is the most common generalist sublineage of Mycobacterium tuberculosis lineage 4 (L4), yet certain L4.3/LAM genotypes appear to be confined to particular geographic regions. This is typically the case of a L4.3/LAM clonal complex (CC), TUN4.3_CC1, which is the most preponderant in Tunisia (61.5% of L4.3/LAM).

Methods

Here, we used whole-genome sequencing data of 346 globally distributed L4 clinical strains, including 278 L4.3/LAM isolates, to reconstruct the evolutionary history of TUN4.3_CC1 and delineate critical genomic changes underpinning its success.

Results and Discussion

Phylogenomic coupled to phylogeographic analyses indicated that TUN4.3_CC1 has evolved locally, being confined mainly to North Africa. Maximum likelihood analyses using the site and branch-site models of the PAML package disclosed strong evidence of positive selection in the gene category "cell wall and cell processes" of TUN4.3_CC1. Collectively, the data indicate that TUN4.3_CC1 has inherited several mutations, which could have potentially contributed to its evolutionary success. Of particular interest are amino acid replacements at the esxK and eccC2 genes of the ESX/Type VII secretion system, which were found to be specific to TUN4.3_CC1, being common to almost all isolates. Because of its homoplastic nature, the esxK mutation could potentially have endowed TUN4.3_CC1 with a selective advantage. Moreover, we noticed the occurrence of additional, previously described homoplasic nonsense mutations in ponA1 and Rv0197. The mutation in the latter gene, a putative oxido-reductase, has previously been shown to be correlated with enhanced transmissibility in vivo. In sum, our findings unveiled several features underpinning the success of a locally evolved L4.3/LAM clonal complex, lending further support to the critical role of genes encoded by the ESX/type VII secretion system.

Evolutionary history and spread of the Mycobacterium tuberculosis Latin American and Mediterranean (L4.3/LAM) sublineage, Tunisia

BACKGROUND

To infer the origin and spread of the Mycobacterium tuberculosis Latin American and Mediterranean (L4.3/LAM) sublineage in a Mediterranean country, Tunisia, where it predominates.

METHODS

We combined Bayesian (STRUCTURE) and maximum likelihood (MIGRAINE) estimation approaches based on a global 24-loci mycobacterial interspersed repetitive units-variable numbers of tandem repeats (MIRU-VNTR24) genotyping dataset consisting of 1573 L4.3/LAM clinical strains from four continents, including 252 isolates originating from Tunisia.

RESULTS

Phylogenetic analyses coupled with Bayesian estimations suggested that the most predominant L4.3/LAM subpopulation in Tunisia (65.07%), which is dominated by a single clonal complex, TUN4.3_CC1 (94.51%), has evolved from an ancestral pool that is restricted to Europe and Africa, contrasting with the remaining L4.3/LAM subpopulations whose ancestry was traced all over the word. Maximum likelihood analysis revealed that TUN4.3_CC1 has been undergoing a demographic expansion since 131 years ago (CI95%: 90.7-205), thus explaining its preponderance relative to the second most predominant CC, TUN4.3_CC2, whose population was found under contraction.

CONCLUSIONS

The preponderance of L4.3/LAM in Tunisia stems from a 130-year expansion process of a locally evolved clone.

Investigating the Diversity of Tuberculosis Spoligotypes with Dimensionality Reduction and Graph Theory

The spoligotype is a graphical description of the CRISPR locus present in Mycobacterium tuberculosis, which has the particularity of having only 68 possible spacers. This spoligotype, which can be easily obtained either in vitro or in silico, allows to have a summary information of lineage or even antibiotic resistance (when known to be associated to a particular cluster) at a lower cost. The objective of this article is to show that this representation is richer than it seems, and that it is under-exploited until now. We first recall an original way to represent these spoligotypes as points in the plane, allowing to highlight possible sub-lineages, particularities in the animal strains, etc. This graphical representation shows clusters and a skeleton in the form of a graph, which led us to see these spoligotypes as vertices of an unconnected directed graph. In this paper, we therefore propose to exploit in detail the description of the variety of spoligotypes using a graph, and we show to what extent such a description can be informative.

Bedaquiline Drug Resistance Emergence Assessment in MDR-TB (DREAM): a 5-Year Prospective In-Vitro Surveillance Study of Bedaquiline and Other Second-Line Drug-Susceptibility Testing in MDR-TB Isolates

Bedaquiline Drug Resistance Emergence Assessment in Multidrug-resistant-tuberculosis (MDR-TB) (DREAM) was a 5-year (2015-2019) phenotypic drug-resistance surveillance study across 11 countries. DREAM assessed the susceptibility of 5036 MDR-TB isolates of bedaquiline-treatment-naïve patients to bedaquiline and other anti-tuberculosis drugs by the 7H9 broth microdilution (BMD) and 7H10/7H11 agar dilution (AD) minimal inhibitory concentration (MIC) methods. Bedaquiline AD MIC quality control (QC) range for the H37Rv reference strain was unchanged, but the BMD MIC QC range (0.015-0.12 μg/ml) was adjusted compared with ranges from a multilaboratory, multicountry reproducibility study conforming to Clinical and Laboratory Standards Institute Tier-2 criteria. Epidemiological cut-off values of 0.12 μg/ml by BMD and 0.25 μg/ml by AD were consistent with previous bedaquiline breakpoints. An area of technical uncertainty or Intermediate category was set at 0.25 μg/ml and 0.5 μg/ml for BMD and AD, respectively. When applied to the 5036 MDR-TB isolates, bedaquiline-susceptible, intermediate and bedaquiline-resistant rates were 97.9%, 1.5% and 0.6%, respectively, for BMD, and 98.8%, 0.8% and 0.4% for AD. Resistance rates were: ofloxacin 35.1%, levofloxacin 34.2%, moxifloxacin 33.3%, 1.5% linezolid and 2% clofazimine. Phenotypic cross resistance between bedaquiline and clofazimine was 0.4% in MDR-TB and 1% in pre-extensively drug-resistant (pre-XDR-TB)/XDR-TB populations. Co-resistance to bedaquiline and linezolid, and clofazimine and linezolid, were 0.1% and 0.3%, respectively, in MDR-TB, and 0.2% and 0.4% in pre-XDR-TB/XDR-TB populations. Resistance rates to bedaquiline appear to be low in the bedaquiline-treatment-naïve population. No treatment-limiting patterns for cross-resistance and co-resistance have been identified with key TB drugs to date.

Whole-genome sequencing as a tool for studying the microevolution of drug-resistant serial Mycobacterium tuberculosis isolates

Treatment of drug-resistant tuberculosis requires extended use of more toxic and less effective drugs and may result in retreatment cases due to failure, abandonment or disease recurrence. It is therefore important to understand the evolutionary process of drug resistance in Mycobacterium tuberculosis. We here in describe the microevolution of drug resistance in serial isolates from six previously treated patients. Drug resistance was initially investigated through phenotypic methods, followed by genotypic approaches. The use of whole-genome sequencing allowed the identification of mutations in the katG, rpsL and rpoB genes associated with drug resistance, including the detection of rare mutations in katG and mixed populations of strains. Molecular docking simulation studies of the impact of observed mutations on isoniazid binding were also performed. Whole-genome sequencing detected 266 single nucleotide polymorphisms between two isolates obtained from one patient, suggesting a case of exogenous reinfection. In conclusion, sequencing technologies can detect rare mutations related to drug resistance, identify subpopulations of resistant strains, and identify diverse populations of strains due to exogenous reinfection, thus improving tuberculosis control by guiding early implementation of appropriate clinical and therapeutic interventions.

Genetic diversity of candidate loci linked to Mycobacterium tuberculosis resistance to bedaquiline, delamanid and pretomanid

Tuberculosis (TB), caused by Mycobacterium tuberculosis, is one of the deadliest infectious diseases worldwide. Multidrug and extensively drug-resistant strains are making disease control difficult, and exhausting treatment options. New anti-TB drugs bedaquiline (BDQ), delamanid (DLM) and pretomanid (PTM) have been approved for the treatment of multi-drug resistant TB, but there is increasing resistance to them. Nine genetic loci strongly linked to resistance have been identified (mmpR5, atpE, and pepQ for BDQ; ddn, fgd1, fbiA, fbiB, fbiC, and fbiD for DLM/PTM). Here we investigated the genetic diversity of these loci across >33,000 M. tuberculosis isolates. In addition, epistatic mutations in mmpL5-mmpS5 as well as variants in ndh, implicated for DLM/PTM resistance in M. smegmatis, were explored. Our analysis revealed 1,227 variants across the nine genes, with the majority (78%) present in isolates collected prior to the roll-out of BDQ and DLM/PTM. We identified phylogenetically-related mutations, which are unlikely to be resistance associated, but also high-impact variants such as frameshifts (e.g. in mmpR5, ddn) with likely functional effects, as well as non-synonymous mutations predominantly in MDR-/XDR-TB strains with predicted protein destabilising effects. Overall, our work provides a comprehensive mutational catalogue for BDQ and DLM/PTM associated genes, which will assist with establishing associations with phenotypic resistance; thereby, improving the understanding of the causative mechanisms of resistance for these drugs, leading to better treatment outcomes.

A Bioinformatics Whole-Genome Sequencing Workflow for Clinical Mycobacterium tuberculosis Complex Isolate Analysis, Validated Using a Reference Collection Extensively Characterized with Conventional Methods and In Silico Approaches

The use of whole-genome sequencing (WGS) for routine typing of bacterial isolates has increased substantially in recent years. For Mycobacterium tuberculosis (MTB), in particular, WGS has the benefit of drastically reducing the time required to generate results compared to most conventional phenotypic methods. Consequently, a multitude of solutions for analyzing WGS MTB data have been developed, but their successful integration in clinical and national reference laboratories is hindered by the requirement for their validation, for which a consensus framework is still largely absent. We developed a bioinformatics workflow for (Illumina) WGS-based routine typing of MTB complex (MTBC) member isolates allowing complete characterization, including (sub)species confirmation and identification (16S, csb/RD, hsp65), single nucleotide polymorphism (SNP)-based antimicrobial resistance (AMR) prediction, and pathogen typing (spoligotyping, SNP barcoding, and core genome multilocus sequence typing). Workflow performance was validated on a per-assay basis using a collection of 238 in-house-sequenced MTBC isolates, extensively characterized with conventional molecular biology-based approaches supplemented with public data. For SNP-based AMR prediction, results from molecular genotyping methods were supplemented with in silico modified data sets, allowing us to greatly increase the set of evaluated mutations. The workflow demonstrated very high performance with performance metrics of >99% for all assays, except for spoligotyping, where sensitivity dropped to ∼90%. The validation framework for our WGS-based bioinformatics workflow can aid in the standardization of bioinformatics tools by the MTB community and other SNP-based applications regardless of the targeted pathogen(s). The bioinformatics workflow is available for academic and nonprofit use through the Galaxy instance of our institute at https://galaxy.sciensano.be.

CRISPRbuilder-TB: "CRISPR-builder for tuberculosis". Exhaustive reconstruction of the CRISPR locus in mycobacterium tuberculosis complex using SRA

Mycobacterium tuberculosis complex (MTC) CRISPR locus diversity has long been studied solely investigating the presence/absence of a known set of spacers. Unveiling the genetic mechanisms of its evolution requires a more exhaustive reconstruction in a large amount of representative strains.

In this article, we point out and resolve, with a new pipeline, the problem of CRISPR reconstruction based directly on short read sequences in M. tuberculosis. We first show that the process we set up, that we coin as “CRISPRbuilder-TB” (https://github.com/cguyeux/CRISPRbuilder-TB), allows an efficient reconstruction of simulated or real CRISPRs, even when including complex evolutionary steps like the insertions of mobile elements. Compared to more generalist tools, the whole process is much more precise and robust, and requires only minimal manual investigation. Second, we show that more than 1/3 of the currently complete genomes available for this complex in the public databases contain largely erroneous CRISPR loci. Third, we highlight how both the classical experimental in vitro approach and the basic in silico spoligotyping provided by existing analytic tools miss a whole diversity of this locus in MTC, by not capturing duplications, spacer and direct repeats variants, and IS6110 insertion locations. This description is extended in a second article that describes MTC-CRISPR diversity and suggests general rules for its evolution. This work opens perspectives for an in-depth exploration of M. tuberculosis CRISPR loci diversity and of mechanisms involved in its evolution and its functionality, as well as its adaptation to other CRISPR locus-harboring bacterial species.

In this article, we tackle the bioinformatical issue of the reconstruction of the Mycobacterium tuberculosis complex CRISPR locus using short read sequences without requiring genome assembly. We first show that many complete genomes, as found in public databases and often reconstructed by de novo assemblies, often contain errors on this locus as well as on other repeated sequences. We provide an in-depth description of our new method, designated as ‘CRISPRbuilder-TB’, and we show that our method provides much more exhaustive and reliable information (on DR variants, spacer diversity, global structure) than Crass and CRISPR_detector. The new and unsuspected genomic diversity we detected is described in a companion paper. Scripts are available to adapt the tool to other species.

Genetic Diversity and Potential Paths of Transmission of Mycobacterium bovis in the Amazon: The Discovery of M. bovis Lineage Lb1 Circulating in South America

Bovine tuberculosis (bTB) has yet to be eradicated in Brazil. Herds of cattle and buffalo are important sources of revenue to people living in the banks of the Amazon River basin. A better understanding of Mycobacterium bovis (M. bovis) populational structure and transmission dynamics affecting these animals can significantly contribute in efforts to improve their sanitary status. Herein, we sequenced the whole genome of 22 M. bovis isolates (15 from buffalo and 7 from cattle) from 10 municipalities in the region of the Lower Amazon River Basin in Brazil and performed phylogenomic analysis and Single Nucleotide Polymorphism (SNP)-based transmission inference to evaluate population structure and transmission networks. Additionally, we compared these genomes to others obtained in unrelated studies in the Marajó Island (n = 15) and worldwide (n = 128) to understand strain diversity in the Amazon and to infer M. bovis lineages. Our results show a higher genomic diversity of M. bovis genomes obtained in the Lower Amazon River region when compared to the Marajó Island, while no significant difference was observed between M. bovis genomes obtained from cattle and buffalo (p ≥ 0.05). This high genetic diversity is reflected by the weak phylogenetic clustering of M. bovis from the Lower Amazon River region based on geographic proximity and in the detection of only two putative transmission clusters in the region. One of these clusters is the first description of inter-species transmission between cattle and buffalo in the Amazon, bringing implications to the bTB control program. Surprisingly, two M. bovis lineages were detected in our dataset, namely Lb1 and Lb3, constituting the first description of Lb1 in South America. Most of the strains of this study (13/22) and all 15 strains of the Marajó Island carried no clonal complex marker, suggesting that the recent lineage classification better describe the diversity of M. bovis in the Amazon.

Novel methods included in SpolLineages tool for fast and precise prediction of Mycobacterium tuberculosis complex spoligotype families

Bioinformatic tools are currently being developed to better understand the Mycobacterium tuberculosis complex (MTBC). Several approaches already exist for the identification of MTBC lineages using classical genotyping methods such as mycobacterial interspersed repetitive units-variable number of tandem DNA repeats and spoligotyping-based families. In the recently released SITVIT2 proprietary database of the Institut Pasteur de la Guadeloupe, a large number of spoligotype families were assigned by either manual curation/expertise or using an in-house algorithm. In this study, we present two complementary data-driven approaches allowing fast and precise family prediction from spoligotyping patterns. The first one is based on data transformation and the use of decision tree classifiers. In contrast, the second one searches for a set of simple rules using binary masks through a specifically designed evolutionary algorithm. The comparison with the three main approaches in the field highlighted the good performances of our contributions and the significant runtime gain. Finally, we propose the 'SpolLineages' software tool (https://github.com/dcouvin/SpolLineages), which implements these approaches for MTBC spoligotype families' identification.

Robust barcoding and identification of Mycobacterium tuberculosis lineages for epidemiological and clinical studies

BACKGROUND

Tuberculosis, caused by bacteria in the Mycobacterium tuberculosis complex (MTBC), is a major global public health burden. Strain-specific genomic diversity in the known lineages of MTBC is an important factor in pathogenesis that may affect virulence, transmissibility, host response and emergence of drug resistance. Fast and accurate tracking of MTBC strains is therefore crucial for infection control, and our previous work developed a 62-single nucleotide polymorphism (SNP) barcode to inform on the phylogenetic identity of 7 human lineages and 64 sub-lineages.

METHODS

To update this barcode, we analysed whole genome sequencing data from 35,298 MTBC isolates (~ 1 million SNPs) covering 9 main lineages and 3 similar animal-related species (M. tuberculosis var. bovis, M. tuberculosis var. caprae and M. tuberculosis var. orygis). The data was partitioned into training (N = 17,903, 50.7%) and test (N = 17,395, 49.3%) sets and were analysed using an integrated phylogenetic tree and population differentiation (FST) statistical approach.

RESULTS

By constructing a phylogenetic tree on the training MTBC isolates, we characterised 90 lineages or sub-lineages or species, of which 30 are new, and identified 421 robust barcoding mutations, of which a minimal set of 90 was selected that included 20 markers from the 62-SNP barcode. The barcoding SNPs (90 and 421) discriminated perfectly the 86 MTBC isolate (sub-)lineages in the test set and could accurately reconstruct the clades across the combined 35k samples.

CONCLUSIONS

The validated 90 SNPs can be used for the rapid diagnosis and tracking of MTBC strains to assist public health surveillance and control. To facilitate this, the SNP markers have now been incorporated into the TB-Profiler informatics platform ( https://github.com/jodyphelan/TBProfiler ).

Successful expansion of Mycobacterium tuberculosis Latin American and Mediterranean sublineage (L4.3/LAM) in Tunisia mainly driven by a single, long-established clonal complex

OBJECTIVES

To explore the evolutionary history of Mycobacterium tuberculosis Latin American and Mediterranean (L4.3/LAM) sublineage in Tunisia, where it predominates.

METHODS

High-resolution genotyping of 252 L4.3/LAM clinical strains was undertaken, and whole-genome sequencing was performed on 31 representative isolates.

RESULTS

Genotyping data coupled with Bayesian analyses split the Tunisian L4.3/LAM strain collection into two divergent entities (65.07% vs 34.92%): a major subpopulation, dominated by a single clonal complex (CC), TUN4.3_CC1 (94.51%); and a minor subpopulation, dominated by TUN4.3_CC2 (42.04%). TUN4.3_CC1 is clearly thriving in Tunisia, accounting for 61.5% of the L4.3/LAM sublineage. TUN4.3_CC1 displayed higher mean allelic richness compared with TUN4.3_CC2 and predominated throughout the entire region, indicating a long-established history. The very low proportion of drug resistance among TUN4.3_CC1 isolates is indicative of their intrinsic ability to spread successfully in the host population. Genomic analyses further confirmed the clear genetic separation between the two main CCs (pairwise fixation index 0.56), and suggested the relatively ancient origin of TUN4.3_CC1. Consistent with its successful expansion, TUN4.3_CC1 showed reduced mean pairwise genetic distance between genomes.

CONCLUSIONS

These findings link the successful expansion of L4.3/LAM in Tunisia to a single long-established clone.

Unexpected diversity of CRISPR unveils some evolutionary patterns of repeated sequences in Mycobacterium tuberculosis

BACKGROUND

Diversity of the CRISPR locus of Mycobacterium tuberculosis complex has been studied since 1997 for molecular epidemiology purposes. By targeting solely the 43 spacers present in the two first sequenced genomes (H37Rv and BCG), it gave a biased idea of CRISPR diversity and ignored diversity in the neighbouring cas-genes.

RESULTS

We set up tailored pipelines to explore the diversity of CRISPR-cas locus in Short Reads. We analyzed data from a representative set of 198 clinical isolates as evidenced by well-characterized SNPs. We found a relatively low diversity in terms of spacers: we recovered only the 68 spacers that had been described in 2000. We found no partial or global inversions in the sequences, letting always the Direct Variant Repeats (DVR) in the same order. In contrast, we found an unexpected diversity in the form of: SNPs in spacers and in Direct Repeats, duplications of various length, and insertions at various locations of the IS6110 insertion sequence, as well as blocks of DVR deletions. The diversity was in part specific to lineages. When reconstructing evolutionary steps of the locus, we found no evidence for SNP reversal. DVR deletions were linked to recombination between IS6110 insertions or between Direct Repeats.

CONCLUSION

This work definitively shows that CRISPR locus of M. tuberculosis did not evolve by classical CRISPR adaptation (incorporation of new spacers) since the last most recent common ancestor of virulent lineages. The evolutionary mechanisms that we discovered could be involved in bacterial adaptation but in a way that remains to be identified.

Bacterial and host determinants of cough aerosol culture positivity in patients with drug-resistant versus drug-susceptible tuberculosis

A burgeoning epidemic of drug-resistant tuberculosis (TB) threatens to derail global control efforts. Although the mechanisms remain poorly clarified, drug-resistant strains are widely believed to be less infectious than drug-susceptible strains. Consequently, we hypothesized that lower proportions of patients with drug-resistant TB would have culturable Mycobacterium tuberculosis from respirable, cough-generated aerosols compared to patients with drug-susceptible TB, and that multiple factors, including mycobacterial genomic variation, would predict culturable cough aerosol production. We enumerated the colony forming units in aerosols (≤10 µm) from 452 patients with TB (227 with drug resistance), compared clinical characteristics, and performed mycobacterial whole-genome sequencing, dormancy phenotyping and drug-susceptibility analyses on M. tuberculosis from sputum. After considering treatment duration, we found that almost half of the patients with drug-resistant TB were cough aerosol culture-positive. Surprisingly, neither mycobacterial genomic variants, lineage, nor dormancy status predicted cough aerosol culture positivity. However, mycobacterial sputum bacillary load and clinical characteristics, including a lower symptom score and stronger cough, were strongly predictive, thereby supporting targeted transmission-limiting interventions. Effective treatment largely abrogated cough aerosol culture positivity; however, this was not always rapid. These data question current paradigms, inform public health strategies and suggest the need to redirect TB transmission-associated research efforts toward host-pathogen interactions.

Mycobacterium bovis: From Genotyping to Genome Sequencing

Mycobacterium bovis is the main pathogen of bovine, zoonotic, and wildlife tuberculosis. Despite the existence of programs for bovine tuberculosis (bTB) control in many regions, the disease remains a challenge for the veterinary and public health sectors, especially in developing countries and in high-income nations with wildlife reservoirs. Current bTB control programs are mostly based on test-and-slaughter, movement restrictions, and post-mortem inspection measures. In certain settings, contact tracing and surveillance has benefited from M. bovis genotyping techniques. More recently, whole-genome sequencing (WGS) has become the preferential technique to inform outbreak response through contact tracing and source identification for many infectious diseases. As the cost per genome decreases, the application of WGS to bTB control programs is inevitable moving forward. However, there are technical challenges in data analyses and interpretation that hinder the implementation of M. bovis WGS as a molecular epidemiology tool. Therefore, the aim of this review is to describe M. bovis genotyping techniques and discuss current standards and challenges of the use of M. bovis WGS for transmission investigation, surveillance, and global lineages distribution. We compiled a series of associated research gaps to be explored with the ultimate goal of implementing M. bovis WGS in a standardized manner in bTB control programs.

Using genomics to understand the origin and dispersion of multidrug and extensively drug resistant tuberculosis in Portugal

Portugal is a low incidence country for tuberculosis (TB) disease. Now figuring among TB low incidence countries, it has since the 1990s reported multidrug resistant and extensively drug resistant (XDR) TB cases, driven predominantly by two strain-types: Lisboa3 and Q1. This study describes the largest characterization of the evolutionary trajectory of M/XDR-TB strains in Portugal, spanning a time-period of two decades. By combining whole-genome sequencing and phenotypic susceptibility data for 207 isolates, we report the geospatial patterns of drug resistant TB, particularly the dispersion of Lisboa3 and Q1 clades, which underly 64.2% and 94.0% of all MDR-TB and XDR-TB isolates, respectively. Genomic-based similarity and a phylogenetic analysis revealed multiple clusters (n = 16) reflecting ongoing and uncontrolled recent transmission of M/XDR-TB, predominantly associated with the Lisboa3 and Q1 clades. These clades are now thought to be evolving in a polycentric mode across multiple geographical districts. The inferred evolutionary history is compatible with MDR- and XDR-TB originating in Portugal in the 70's and 80's, respectively, but with subsequent multiple emergence events of MDR and XDR-TB particularly involving the Lisboa3 clade. A SNP barcode was defined for Lisboa3 and Q1 and comparison with a phylogeny of global strain-types (n = 28 385) revealed the presence of Lisboa3 and Q1 strains in Europe, South America and Africa. In summary, Portugal displays an unusual and unique epidemiological setting shaped by >40 years of uncontrolled circulation of two main phylogenetic clades, leading to a sympatric evolutionary trajectory towards XDR-TB with the potential for global reach.

A landscape of genomic alterations at the root of a near-untreatable tuberculosis epidemic

BACKGROUND

Atypical Beijing genotype Mycobacterium tuberculosis strains are widespread in South Africa and have acquired resistance to up to 13 drugs on multiple occasions. It is puzzling that these strains have retained fitness and transmissibility despite the potential fitness cost associated with drug resistance mutations.

METHODS

We conducted Illumina sequencing of 211 Beijing genotype M. tuberculosis isolates to facilitate the detection of genomic features that may promote acquisition of drug resistance and restore fitness in highly resistant atypical Beijing forms. Phylogenetic and comparative genomic analysis was done to determine changes that are unique to the resistant strains that also transmit well. Minimum inhibitory concentration (MIC) determination for streptomycin and bedaquiline was done for a limited number of isolates to demonstrate a difference in MIC between isolates with and without certain variants.

RESULTS

Phylogenetic analysis confirmed that two clades of atypical Beijing strains have independently developed resistance to virtually all the potent drugs included in standard (pre-bedaquiline) drug-resistant TB treatment regimens. We show that undetected drug resistance in a progenitor strain was likely instrumental in this resistance acquisition. In this cohort, ethionamide (ethA A381P) resistance would be missed in first-line drug-susceptible isolates, and streptomycin (gidB L79S) resistance may be missed due to an MIC close to the critical concentration. Subsequent inadequate treatment historically led to amplification of resistance and facilitated spread of the strains. Bedaquiline resistance was found in a small number of isolates, despite lack of exposure to the drug. The highly resistant clades also carry inhA promoter mutations, which arose after ethA and katG mutations. In these isolates, inhA promoter mutations do not alter drug resistance, suggesting a possible alternative role.

CONCLUSION

The presence of the ethA mutation in otherwise susceptible isolates from ethionamide-naïve patients demonstrates that known exposure is not an adequate indicator of drug susceptibility. Similarly, it is demonstrated that bedaquiline resistance can occur without exposure to the drug. Inappropriate treatment regimens, due to missed resistance, leads to amplification of resistance, and transmission. We put these results into the context of current WHO treatment regimens, underscoring the risks of treatment without knowledge of the full drug resistance profile.

Genomic Analysis of Mycobacterium tuberculosis Isolates and Construction of a Beijing Lineage Reference Genome

Tuberculosis (TB), an infectious disease caused by Mycobacterium tuberculosis, kills over 1 million people worldwide annually. Development of drug resistance (DR) in the pathogen is a major challenge for TB control. We conducted whole-genome analysis of seven Taiwan M. tuberculosis isolates: One drug susceptible (DS) and five DR Beijing lineage isolates and one DR Euro-American lineage isolate. Developing a new method for DR mutation identification and applying it to the next-generation sequencing (NGS) data from the 6 Beijing lineage isolates, we identified 13 known and 6 candidate DR mutations and provided experimental support for 4 of them. We assembled the genomes of one DS and two DR Beijing lineage isolates and the Euro-American lineage isolate using NGS data. Moreover, using both PacBio and NGS sequencing data, we obtained a high-quality assembly of an extensive DR Beijing lineage isolate. Comparative analysis of these five newly assembled genomes and two published complete genomes revealed a large number of genetic changes, including gene gains and losses, indels and translocations, suggesting rapid evolution of M. tuberculosis. We found the MazEF toxin–antitoxin system in all the seven isolates studied and several interesting mutations in MazEF proteins. Finally, we used the four assembled Beijing lineage genomes to construct a high-quality Beijing lineage reference genome that is DS and contains all the genes in the four genomes. It contains 212 genes not found in the standard reference H37Rv, which is Euro-American. It is therefore a better reference than H37Rv for the Beijing lineage, the predominant lineage in Asia.

Whole genome sequencing of drug resistant Mycobacterium tuberculosis isolates from a high burden tuberculosis region of North West Pakistan

Tuberculosis (TB), caused by Mycobacterium tuberculosis bacteria, is a leading infectious cause of mortality worldwide, including in Pakistan. Drug resistant M. tuberculosis is an emerging threat for TB control, making it important to detect the underlying genetic mutations, and thereby inform treatment decision making and prevent transmission. Whole genome sequencing has emerged as the new diagnostic to reliably predict drug resistance within a clinically relevant time frame, and its deployment will have the greatest impact on TB control in highly endemic regions. To evaluate the mutations leading to drug resistance and to assess for evidence of the transmission of resistant strains, 81 M. tuberculosis samples from Khyber Pakhtunkhwa province (North West Pakistan) were subjected to whole genome sequencing and standard drug susceptibility testing for eleven anti-TB drugs. We found the majority of M. tuberculosis isolates were the CAS/Delhi strain-type (lineage 3; n = 57; 70.4%) and multi-drug resistant (MDR; n = 62; 76.5%). The most frequent resistance mutations were observed in the katG and rpoB genes, conferring resistance to isoniazid and rifampicin respectively. Mutations were also observed in genes conferring resistance to other first and second-line drugs, including in pncA (pyrazinamide), embB (ethambutol), gyrA (fluoroquinolones), rrs (aminoglycosides), rpsL, rrs and giB (streptomycin) loci. Whilst the majority of mutations have been reported in global datasets, we describe unreported putative resistance markers in katG, ethA (ethionamide), gyrA and gyrB (fluoroquinolones), and pncA. Analysis of the mutations revealed that acquisition of rifampicin resistance often preceded isoniazid in our isolates. We also observed a high proportion (17.6%) of pre-MDR isolates with fluoroquinolone resistance markers, potentially due to unregulated anti-TB drug use. Our isolates were compared to previously sequenced strains from Pakistan in a combined phylogenetic tree analysis. The presence of lineage 2 was only observed in our isolates. Using a cut-off of less than ten genome-wide mutation differences between isolates, a transmission analysis revealed 18 M. tuberculosis isolates clustering within eight networks, thereby providing evidence of drug-resistant TB transmission in the Khyber Pakhtunkhwa province. Overall, we have demonstrated that drug-resistant TB isolates are circulating and transmitted in North West Pakistan. Further, we have shown the usefulness of whole genome sequencing as a diagnostic tool for characterizing M. tuberculosis isolates, which will assist future epidemiological studies and disease control activities in Pakistan.

Mycobacterium tuberculosis whole genome sequencing provides insights into the Manila strain and drug-resistance mutations in the Philippines

The Philippines has a high incidence of tuberculosis disease (TB), with an increasing prevalence of multidrug-resistant Mycobacterium tuberculosis (MDR-TB) strains making its control difficult. Although the M. tuberculosis "Manila" ancient lineage 1 strain-type is thought to be prevalent in the country, with evidence of export to others, little is known about the genetic diversity of circulating strains. By whole genome sequencing (WGS) 178 isolates from the Philippines National Drug Resistance Survey, we found the majority (143/178; 80.3%) belonged to the lineage 1 Manila clade, with the minority belonging to lineages 4 (European-American; n = 33) and 2 (East Asian; n = 2). A high proportion were found to be multidrug-resistant (34/178; 19.1%), established through highly concordant laboratory drug susceptibility testing and in silico prediction methods. Some MDR-TB isolates had near identical genomic variation, providing potential evidence of transmission. By placing the Philippine isolates within a phylogeny of global M. tuberculosis (n > 17,000), we established that they are genetically similar to those observed outside the country, including a clade of Manila-like strain-types in Thailand. An analysis of the phylogeny revealed a set of ~200 SNPs that are specific for the Manila strain-type, and a subset can be used within a molecular barcode. Sixty-eight mutations known to be associated with 10 anti-TB drug resistance were identified in the Philippine strains, and all have been observed in other populations. Whilst nine putative streptomycin resistance conferring markers in gid (8) and rrs (1) genes appear to be novel and with functional consequences. Overall, this study provides an important baseline characterisation of M. tuberculosis genetic diversity for the Philippines, and will fill a gap in global datasets and aid the development of a nation-wide database for epidemiological studies and clinical decision making. Further, by establishing a molecular barcode for detecting Manila strains it will assist with the design of diagnostic tools for disease control activities.

Mycobacterium tuberculosis lineage 1 genetic diversity in Pará, Brazil, suggests common ancestry with east-African isolates potentially linked to historical slave trade

Lineage 1 (L1) is one of seven Mycobacterium tuberculosis complex (MTBC) lineages. The objective of this study was to improve the complex taxonomy of L1 using phylogenetic SNPs, and to look for the origin of the main L1 sublineage prevalent in Para, Brazil. We developed a high-throughput SNPs-typing assay based on 12-L1-specific SNPs. This assay allowed us to experimentally retrieve SNP patterns on nine of these twelve SNPs in 277 isolates previously tentatively assigned to L1 spoligotyping-based sublineages. Three collections were used: Pará-Brazil (71); RIVM, the Netherlands (102), Madagascar (104). One-hundred more results were generated in Silico using the PolyTB database. Based on the final SNPs combination, the samples were classified into 11 clusters (C1-C11). Most isolates within a SNP-based cluster shared a mutual spoligotyping-defined lineage. However, L1/EAI1-SOM (SIT48) and L1/EAI6-BGD1 (SIT591) showed a poor correlation with SNP data and are not monophyletic. L1/EAI8-MDG and L1/EAI3-IND belonged to C5; this result suggests that they share a common ancestor. L1.1.3/SIT129, a spoligotype pattern found in SNPs-cluster C6, was found to be shared between Pará/Brazil and Malawi. SIT129 was independently found to be highly prevalent in Mozambique, which suggests a migration history from East-Africa to Brazil during the 16th-18th slave trade period to Northern Brazil.

Genomic analysis of the emergence of drug-resistant strains of Mycobacterium tuberculosis in the Middle East

Tuberculosis (TB) represents a significant challenge to public health authorities, especially with the emergence of drug-resistant (DR) and multidrug-resistant (MDR) isolates of Mycobacterium tuberculosis. We sought to examine the genomic variations among recently isolated strains of M. tuberculosis in two closely related countries with different population demography in the Middle East. Clinical isolates of M. tuberculosis from both Egypt and Saudi Arabia were subjected to phenotypic and genotypic analysis on gene and genome-wide levels. Isolates with MDR phenotypes were highly prevalent in Egypt (up to 35%) despite its relatively stable population structure (sympatric pattern). MDR-TB isolates were not identified in the isolates from Saudi Arabia despite its active guest worker program (allopatric pattern). However, tuberculosis isolates from Saudi Arabia, where lineage 4 was more prevalent (>65%), showed more diversity than isolates from Egypt, where lineage 3 was the most prevalent (>75%). Phylogenetic and molecular dating analyses indicated that lineages from Egypt were recently diverged (~78 years), whereas those from Saudi Arabia were diverged by over 200 years. Interestingly, DR isolates did not appear to cluster together or spread more widely than drug-sensitive isolates, suggesting poor treatment as the main cause for emergence of drug resistance rather than more virulence or more capacity to persist.

Highlights on the Application of Genomics and Bioinformatics in the Fight Against Infectious Diseases: Challenges and Opportunities in Africa

Genomics and bioinformatics are increasingly contributing to our understanding of infectious diseases caused by bacterial pathogens such as Mycobacterium tuberculosis and parasites such as Plasmodium falciparum. This ranges from investigations of disease outbreaks and pathogenesis, host and pathogen genomic variation, and host immune evasion mechanisms to identification of potential diagnostic markers and vaccine targets. High throughput genomics data generated from pathogens and animal models can be combined with host genomics and patients’ health records to give advice on treatment options as well as potential drug and vaccine interactions. However, despite accounting for the highest burden of infectious diseases, Africa has the lowest research output on infectious disease genomics. Here we review the contributions of genomics and bioinformatics to the management of infectious diseases of serious public health concern in Africa including tuberculosis (TB), dengue fever, malaria and filariasis. Furthermore, we discuss how genomics and bioinformatics can be applied to identify drug and vaccine targets. We conclude by identifying challenges to genomics research in Africa and highlighting how these can be overcome where possible.

Evidence for Host-Bacterial Co-evolution via Genome Sequence Analysis of 480 Thai Mycobacterium tuberculosis Lineage 1 Isolates

Tuberculosis presents a global health challenge. Mycobacterium tuberculosis is divided into several lineages, each with a different geographical distribution. M. tuberculosis lineage 1 (L1) is common in the high-burden areas in East Africa and Southeast Asia. Although the founder effect contributes significantly to the phylogeographic profile, co-evolution between the host and M. tuberculosis may also play a role. Here, we reported the genomic analysis of 480 L1 isolates from patients in northern Thailand. The studied bacterial population was genetically diverse, allowing the identification of a total of 18 sublineages distributed into three major clades. The majority of isolates belonged to L1.1 followed by L1.2.1 and L1.2.2. Comparison of the single nucleotide variant (SNV) phylogenetic tree and the clades defined by spoligotyping revealed some monophyletic clades representing EAI2_MNL, EAI2_NTM and EAI6_BGD1 spoligotypes. Our work demonstrates that ambiguity in spoligotype assignment could be partially resolved if the entire DR region is investigated. Using the information to map L1 diversity across Southeast Asia highlighted differences in the dominant strain-types in each individual country, despite extensive interactions between populations over time. This finding supported the hypothesis that there is co-evolution between the bacteria and the host, and have implications for tuberculosis disease control.

Unexpected Genomic and Phenotypic Diversity of Mycobacterium africanum Lineage 5 Affects Drug Resistance, Protein Secretion, and Immunogenicity

Mycobacterium africanum consists of Lineages L5 and L6 of the Mycobacterium tuberculosis complex (MTBC) and causes human tuberculosis in specific regions of Western Africa, but is generally not transmitted in other parts of the world. Since M. africanum is evolutionarily closely placed between the globally dispersed Mycobacterium tuberculosis and animal-adapted MTBC-members, these lineages provide valuable insight into M. tuberculosis evolution. Here, we have collected 15 M. africanum L5 strains isolated in France over 4 decades. Illumina sequencing and phylogenomic analysis revealed a previously underappreciated diversity within L5, which consists of distinct sublineages. L5 strains caused relatively high levels of extrapulmonary tuberculosis and included multi- and extensively drug-resistant isolates, especially in the newly defined sublineage L5.2. The specific L5 sublineages also exhibit distinct phenotypic characteristics related to in vitro growth, protein secretion and in vivo immunogenicity. In particular, we identified a PE_PGRS and PPE-MPTR secretion defect specific for sublineage L5.2, which was independent of PPE38. Furthermore, L5 isolates were able to efficiently secrete and induce immune responses against ESX-1 substrates contrary to previous predictions. These phenotypes of Type VII protein secretion and immunogenicity provide valuable information to better link genome sequences to phenotypic traits and thereby understand the evolution of the MTBC.

Whole genome SNP analysis suggests unique virulence factor differences of the Beijing and Manila families of Mycobacterium tuberculosis found in Hawaii

While tuberculosis (TB) remains a global disease, the WHO estimates that 62% of the incident TB cases in 2016 occurred in the WHO South-East Asia and Western Pacific regions. TB in the Pacific is composed predominantly of two genetic families of Mycobacterium tuberculosis (Mtb): Beijing and Manila. The Manila family is historically under-studied relative to the families that comprise the majority of TB in Europe and North America (e.g. lineage 4), and it remains unclear why this lineage has persisted in Filipino populations despite the predominance of more globally successful Mtb lineages in most of the world. The Beijing family is of particular interest as it is increasingly associated with drug resistance throughout the world. Both of these lineages are important to the State of Hawaii, where they comprise over two-thirds of TB cases. Here, we performed whole genome sequencing on 82 Beijing family, Manila family, and outgroup clinical Mtb isolates from Hawaii to identify lineage-specific SNPs (SNPs found in all isolates from their respective families, and exclusively in those families) in established virulence factor genes. Six non-silent lineage-specific virulence factor SNPs were found in the Beijing family, including mutations in alternative sigma factor sigG and polyketide synthases pks5 and pks7. The Manila family displayed more than eleven non-silent lineage-specific and characteristic virulence factor mutations, including in genes coding for MCE-family protein Mce1B, two mutations in fatty-acid-AMP ligase FadD26, and virulence-regulating transcriptional regulator VirS. This study further identified an ancient clade that shared some virulence factor mutations with the Manila family, and investigated the relationship of those and other “Manila-like” spoligotypes to the Manila family with this SNP dataset. This work identified a set of virulence genes that are worth pursuing to determine potential differences in transmission or virulence displayed by these two Mtb families.

Genome-wide analysis of multi- and extensively drug-resistant Mycobacterium tuberculosis

To characterize the genetic determinants of resistance to antituberculosis drugs, we performed a genome-wide association study (GWAS) of 6,465 Mycobacterium tuberculosis clinical isolates from more than 30 countries. A GWAS approach within a mixed-regression framework was followed by a phylogenetics-based test for independent mutations. In addition to mutations in established and recently described resistance-associated genes, novel mutations were discovered for resistance to cycloserine, ethionamide and para-aminosalicylic acid. The capacity to detect mutations associated with resistance to ethionamide, pyrazinamide, capreomycin, cycloserine and para-aminosalicylic acid was enhanced by inclusion of insertions and deletions. Odds ratios for mutations within candidate genes were found to reflect levels of resistance. New epistatic relationships between candidate drug-resistance-associated genes were identified. Findings also suggest the involvement of efflux pumps (drrA and Rv2688c) in the emergence of resistance. This study will inform the design of new diagnostic tests and expedite the investigation of resistance and compensatory epistatic mechanisms.

Multi-clonal evolution of multi-drug-resistant/extensively drug-resistant Mycobacterium tuberculosis in a high-prevalence setting of Papua New Guinea for over three decades

An outbreak of multi-drug resistant (MDR) tuberculosis (TB) has been reported on Daru Island, Papua New Guinea. Mycobacterium tuberculosis strains driving this outbreak and the temporal accrual of drug resistance mutations have not been described. Whole genome sequencing of 100 of 165 clinical isolates referred from Daru General Hospital to the Supranational reference laboratory, Brisbane, during 2012–2015 revealed that 95 belonged to a single modern Beijing sub-lineage strain. Molecular dating suggested acquisition of streptomycin and isoniazid resistance in the 1960s, with potentially enhanced virulence mediated by an mycP1 mutation. The Beijing sub-lineage strain demonstrated a high degree of co-resistance between isoniazid and ethionamide (80/95; 84.2 %) attributed to an inhA promoter mutation combined with inhA and ndh coding mutations. Multi-drug resistance, observed in 78/95 samples, emerged with the acquisition of a typical rpoB mutation together with a compensatory rpoC mutation in the 1980s. There was independent acquisition of fluoroquinolone and aminoglycoside resistance, and evidence of local transmission of extensively drug resistant (XDR) strains from 2009. These findings underline the importance of whole genome sequencing in informing an effective public health response to MDR/XDR TB.

Whole genome sequencing of the monomorphic pathogen Mycobacterium bovis reveals local differentiation of cattle clinical isolates

Background

Bovine tuberculosis (bTB) poses serious risks to animal welfare and economy, as well as to public health as a zoonosis. Its etiological agent, Mycobacterium bovis, belongs to the Mycobacterium tuberculosis complex (MTBC), a group of genetically monomorphic organisms featured by a remarkably high overall nucleotide identity (99.9%). Indeed, this characteristic is of major concern for correct typing and determination of strain-specific traits based on sequence diversity. Due to its historical economic dependence on cattle production, Uruguay is deeply affected by the prevailing incidence of Mycobacterium bovis. With the world’s highest number of cattle per human, and its intensive cattle production, Uruguay represents a particularly suited setting to evaluate genomic variability among isolates, and the diversity traits associated to this pathogen.

Results

We compared 186 genomes from MTBC strains isolated worldwide, and found a highly structured population in M. bovis. The analysis of 23 new M. bovis genomes, belonging to strains isolated in Uruguay evidenced three groups present in the country. Despite presenting an expected highly conserved genomic structure and sequence, these strains segregate into a clustered manner within the worldwide phylogeny. Analysis of the non-pe/ppe differential areas against a reference genome defined four main sources of variability, namely: regions of difference (RD), variable genes, duplications and novel genes. RDs and variant analysis segregated the strains into clusters that are concordant with their spoligotype identities. Due to its high homoplasy rate, spoligotyping failed to reflect the true genomic diversity among worldwide representative strains, however, it remains a good indicator for closely related populations.

Conclusions

This study introduces a comprehensive population structure analysis of worldwide M. bovis isolates. The incorporation and analysis of 23 novel Uruguayan M. bovis genomes, sheds light onto the genomic diversity of this pathogen, evidencing the existence of greater genetic variability among strains than previously contemplated.

Electronic supplementary material

The online version of this article (10.1186/s12864-017-4249-6) contains supplementary material, which is available to authorized users.

Complete Genome Sequencing of Mycobacterium bovis SP38 and Comparative Genomics of Mycobacterium bovis and M. tuberculosis Strains

Mycobacterium bovis causes bovine tuberculosis and is the main organism responsible for zoonotic tuberculosis in humans. We performed the sequencing, assembly and annotation of a Brazilian strain of M. bovis named SP38, and performed comparative genomics of M. bovis genomes deposited in GenBank. M. bovis SP38 has a traditional tuberculous mycobacterium genome of 4,347,648 bp, with 65.5% GC, and 4,216 genes. The majority of CDSs (2,805, 69.3%) have predictive function, while 1,206 (30.07%) are hypothetical. For comparative analysis, 31 M. bovis, 32 M. bovis BCG, and 23 Mycobacterium tuberculosis genomes available in GenBank were selected. M. bovis RDs (regions of difference) and Clonal Complexes (CC) were identified in silico. Genome dynamics of bacterial groups were analyzed by gene orthology and polymorphic sites identification. M. bovis polymorphic sites were used to construct a phylogenetic tree. Our RD analyses resulted in the exclusion of three genomes, mistakenly annotated as virulent M. bovis. M. bovis SP38 along with strain 35 represent the first report of CC European 2 in Brazil, whereas two other M. bovis strains failed to be classified within current CC. Results of M. bovis orthologous genes analysis suggest a process of genome remodeling through genomic decay and gene duplication. Quantification, pairwise comparisons and distribution analyses of polymorphic sites demonstrate greater genetic variability of M. tuberculosis when compared to M. bovis and M. bovis BCG (p ≤ 0.05), indicating that currently defined M. tuberculosis lineages are more genetically diverse than M. bovis CC and animal-adapted MTC (M. tuberculosis Complex) species. As expected, polymorphic sites annotation shows that M. bovis BCG are subjected to different evolutionary pressures when compared to virulent mycobacteria. Lastly, M. bovis phylogeny indicates that polymorphic sites may be used as markers of M. bovis lineages in association with CC. Our findings highlight the need to better understand host-pathogen co-evolution in genetically homogeneous and/or diverse host populations, considering the fact that M. bovis has a broader host range when compared to M. tuberculosis. Also, the identification of M. bovis genomes not classified within CC indicates that the diversity of M. bovis lineages may be larger than previously thought or that current classification should be reviewed.

Spoligotyping and whole-genome sequencing analysis of lineage 1 strains of Mycobacterium tuberculosis in Da Nang, Vietnam

Background

Spacer oligonucleotide typing (spoligotyping), a widely used, classical genotyping method for Mycobacterium tuberculosis complex (MTBC), is a PCR-based dot-blot hybridization technique to detect the genetic diversity of the direct repeat (DR) region. Of the seven major MTBC lineages in the world, lineage 1 (Indo-Oceanic) mostly corresponds to the East African–Indian (EAI) spoligotype family in East Africa and Southeast Asia.

Objectives

We investigated the genomic features of Vietnamese lineage 1 strains, comparing spoligotype patterns using whole-genome sequencing (WGS) data.

Methods

M. tuberculosis strains isolated in Da Nang, Vietnam were subjected to conventional spoligotyping, followed by WGS analysis using a high-throughput sequencer. Vietnamese lineage 1 strains were further analyzed with other lineage 1 strains obtained from a public database.

Results

Indicating a major spoligotype in Da Nang, 86 (46.2%) of the 186 isolates belonged to the EAI family or lineage 1. Although typical EAI4-VNM strains are characterized by the deletion of spacers 26 and 27, 65 (75.6%) showed ambiguous signals on spacer 26. De novo assembly of the entire DR region and in silico spoligotyping analysis suggested the absence of spacer 26, and direct sequencing revealed that the 17^th spacer sequence not used for conventional typing, was cross-hybridized to the spacer 26 probe. Vietnamese EAI4-VNM, other EAI-like strains, and those showing a non-EAI pattern lacking many spacers formed a monophyletic group separate from other EAI families in the world.

Conclusion

Information about the alignment of spacers in the entire DR region obtained from WGS data provides a clue for the determination of experimentally ambiguous spoligo patterns. WGS data also helped to analyze the hidden relationships between apparently distinct spoligo patterns.

Application of whole genome sequence analysis to the study of Mycobacterium tuberculosis in Nunavut, Canada

Canada has one of the lowest rates of tuberculosis (TB) in the world, however, among certain sub-populations, disease incidence rates approach those observed in sub-Saharan Africa, and other high incidence regions. In this study, we applied mycobacterial interspersed repetitive unit (MIRU) variable number of tandem repeat (VNTR) and whole genome sequencing (WGS) to the analysis of Mycobacterium tuberculosis isolates obtained from Northern communities in the territory of Nunavut. WGS was carried out using the Illumina MiSeq, with identified variants used to infer phylogenetic relationships and annotated to infer functional implications. Additionally, the sequencing data from these isolates were augmented with publically available WGS to evaluate data from the Nunavut outbreak in the broader Canadian context. In this study, isolates could be classified into four major clusters by MIRU-VNTR analysis. These could be further resolved into sub-clusters using WGS. No evidence for antimicrobial resistance, either genetic or phenotypic, was observed in this cohort. Among most subjects with multiple samples, reactivation/incomplete treatment likely contributed to recurrence. However, isolates from two subjects appeared more likely to have occurred via reinfection, based on the large number of genomic single nucleotide variants detected. Finally, although quite distinct from previously reported Canadian MTB strains, isolates obtained from Nunavut clustered most closely with a cohort of samples originating in the Nunavik region of Northern Quebec. This study demonstrates the benefit of using WGS for discriminatory analysis of MTB in Canada, especially in high incidence regions. It further emphasizes the importance of focusing epidemiological intervention efforts on interrupting transmission chains of endemic TB throughout Northern communities, rather than relying on strategies applied in regions where the majority of TB cases result from importation of foreign strains.

Whole genome sequencing of Mycobacterium bovis to obtain molecular fingerprints in human and cattle isolates from Baja California, Mexico

OBJECTIVES

To determine genetic diversity by comparing the whole genome sequences of cattle and human Mycobacterium bovis isolates from Baja California.

METHODS

A whole genome sequencing strategy was used to obtain the molecular fingerprints of 172 isolates of M. bovis obtained from Baja California, Mexico; 155 isolates were from cattle and 17 isolates were from humans. Spoligotypes were characterized in silico and single nucleotide polymorphism (SNP) differences between the isolates were evaluated.

RESULTS

A total of 12 M. bovis spoligotype patterns were identified in cattle and humans. Two predominant spoligotypes patterns were seen in both cattle and humans: SB0145 and SB1040. The SB0145 spoligotype represented 59% of cattle isolates (n=91) and 65% of human isolates (n=11), while the SB1040 spoligotype represented 30% of cattle isolates (n=47) and 30% of human isolates (n=5). When evaluating SNP differences, the human isolates were intimately intertwined with the cattle isolates.

CONCLUSIONS

All isolates from humans had spoligotype patterns that matched those observed in the cattle isolates, and all human isolates shared common ancestors with cattle in Baja California based on SNP analysis. This suggests that most human tuberculosis caused by M. bovis in Baja California is derived from M. bovis circulating in Baja California cattle. These results reinforce the importance of bovine tuberculosis surveillance and control in this region.

Progenitor strain introduction of Mycobacterium bovis at the wildlife-livestock interface can lead to clonal expansion of the disease in a single ecosystem

Mycobacterium bovis infects multiple wildlife species and domesticated cattle across South Africa, and negatively impacts on livestock trade and movement of wildlife for conservation purposes. M. bovis infection was first reported in the Kruger National Park (KNP) in South Africa during the 1990s, and has since spread to infect numerous animal host species throughout the park and across South Africa. Whole genome sequencing data of 17 M. bovis isolates were analyzed to investigate the genomic diversity among M. bovis isolates causing disease in different animal host species from various locations in South Africa. M. bovis strains analyzed in this study are geographic rather than host species-specific. The clonal expansion of M. bovis in the KNP highlights the effect of an introduction of a transmissible infectious disease leading to a rising epidemic in wildlife, and emphasizes the importance of disease control and movement restriction of species that serve as disease reservoirs. In conclusion, the point source introduction of a single M. bovis strain type in the KNP ecosystem lead to an M. bovis outbreak in this area that affects various host species and poses an infection risk in neighboring rural communities where HIV prevalence is high.

Use of whole-genome sequencing to distinguish relapse from reinfection in a completed tuberculosis clinical trial

BACKGROUND

RIFAQUIN was a tuberculosis chemotherapy trial in southern Africa including regimens with high-dose rifapentine with moxifloxacin. Here, the application of whole-genome sequencing (WGS) is evaluated within RIFAQUIN for identifying new infections in treated patients as either relapses or reinfections. WGS is further compared with mycobacterial interspersed repetitive units-variable number tandem repeats (MIRU-VNTR) typing. This is the first report of WGS being used to evaluate new infections in a completed clinical trial for which all treatment and epidemiological data are available for analysis.

METHODS

DNA from 36 paired samples of Mycobacterium tuberculosis cultured from patients before and after treatment was typed using 24-loci MIRU-VNTR, in silico spoligotyping and WGS. Following WGS, the sequences were mapped against the reference strain H37Rv, the single-nucleotide polymorphism (SNP) differences between pairs were identified, and a phylogenetic reconstruction was performed.

RESULTS

WGS indicated that 32 of the paired samples had a very low number of SNP differences (0-5; likely relapses). One pair had an intermediate number of SNP differences, and was likely the result of a mixed infection with a pre-treatment minor genotype that was highly related to the post-treatment genotype; this was reclassified as a relapse, in contrast to the MIRU-VNTR result. The remaining three pairs had very high SNP differences (>750; likely reinfections).

CONCLUSIONS

WGS and MIRU-VNTR both similarly differentiated relapses and reinfections, but WGS provided significant extra information. The low proportion of reinfections seen suggests that in standard chemotherapy trials with up to 24 months of follow-up, typing the strains brings little benefit to an analysis of the trial outcome in terms of differentiating relapse and reinfection. However, there is a benefit to using WGS as compared to MIRU-VNTR in terms of the additional genotype information obtained, in particular for defining the presence of mixed infections and the potential to identify known and novel drug-resistance markers.

Structure and variation of CRISPR and CRISPR-flanking regions in deleted-direct repeat region Mycobacterium tuberculosis complex strains

Background

CRISPR and CRISPR-flanking genomic regions are important for molecular epidemiology of Mycobacterium tuberculosis complex (MTBC) strains, and potentially for adaptive immunity to phage and plasmid DNA, and endogenous roles in the bacterium. Genotyping in the Israel National Mycobacterium Reference Center Tel-Aviv of over 1500 MTBC strains from 2008–2013 showed three strains with validated negative 43-spacer spoligotypes, that is, with putatively deleted direct repeat regions (deleted-DR/CRISPR regions). Two isolates of each of three negative spoligotype MTBC (a total of 6 isolates) were subjected to Next Generation Sequencing (NGS). As positive controls, NGS was performed for three intact-DR isolates belonging to T3_Eth, the largest multiple-drug-resistant (MDR)-containing African-origin cluster in Israel. Other controls consisted of NGS reads and complete whole genome sequences from GenBank for 20 intact-DR MTBC and for 1 deleted-DR MTBC strain recognized as CAS by its defining RD deletion.

Results

NGS reads from negative spoligotype MTBC mapped to reference H37Rv NC_000962.3 suggested that the DR/CRISPR regions were completely deleted except for retention of the middle IS6110 mobile element. Clonally specific deletion of CRISPR-flanking genes also was observed, including deletion of at least cas2 and cas1 genes. Genomic RD deletions defined lineages corresponding to the major spoligotype families Beijing, EAI, and Haarlem, consistent with 24 loci MIRU-VNTR profiles. Analysis of NGS reads, and analysis of contigs obtained by manual PCR confirmed that all 43 gold standard DR/CRISPR spacers were missing in the deleted-DR genomes.

Conclusions

Although many negative spoligotype strains are recorded as spoligotype-international-type (SIT) 2669 in the SITVIT international database, this is the first time to our knowledge that it has been shown that negative spoligotype strains are found in at least 4 different 24 loci MIRU-VNTR and RD deletion families. We report for the first time negative spoligotype-associated total loss of CRISPR region spacers and repeats, with accompanying clonally specific loss of flanking genes, including at least CRISPR-associated genes cas2 and cas1. Since cas1 deleted E.coli shows increased sensitivity to DNA damage and impaired chromosomal segregation, we discussed the possibility of a similar phenotype in the deleted-DR strains and Beijing family strains as both lack the cas1 gene.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-017-3560-6) contains supplementary material, which is available to authorized users.

In silico region of difference (RD) analysis of Mycobacterium tuberculosis complex from sequence reads using RD-Analyzer

BACKGROUND

Whole-genome sequencing is increasingly used in clinical diagnosis of tuberculosis and study of Mycobacterium tuberculosis complex (MTC). MTC consists of several genetically homogenous mycobacteria species which can cause tuberculosis in humans and animals. Regions of difference (RDs) are commonly regarded as gold standard genetic markers for MTC classification.

RESULTS

We develop RD-Analyzer, a tool that can accurately infer the species and lineage of MTC isolates from sequence reads based on the presence and absence of a set of 31 RDs. Applied on a publicly available diverse set of 377 sequenced MTC isolates from known major species and lineages, RD-Analyzer achieved an accuracy of 98.14 % (370/377) in species prediction and a concordance of 98.47 % (257/261) in Mycobacterium tuberculosis lineage prediction compared to predictions based on single nucleotide polymorphism markers. By comparing respective sequencing read depths on each genomic position between isolates of different sublineages, we were able to identify the known RD markers in different sublineages of Lineage 4 and provide support for six potential delineating markers having high sensitivities and specificities for sublineage prediction. An extended version of RD-Analyzer was thus developed to allow user-defined RDs for lineage prediction.

CONCLUSIONS

RD-Analyzer is a useful and accurate tool for species, lineage and sublineage prediction using known RDs of MTC from sequence reads and is extendable to accepting user-defined RDs for analysis. RD-Analyzer is written in Python and is freely available at https://github.com/xiaeryu/RD-Analyzer .

Methodological and Clinical Aspects of the Molecular Epidemiology of Mycobacterium tuberculosis and Other Mycobacteria

Molecular typing has revolutionized epidemiological studies of infectious diseases, including those of a mycobacterial etiology. With the advent of fingerprinting techniques, many traditional concepts regarding transmission, infectivity, or pathogenicity of mycobacterial bacilli have been revisited, and their conventional interpretations have been challenged. Since the mid-1990s, when the first typing methods were introduced, a plethora of other modalities have been proposed. So-called molecular epidemiology has become an essential subdiscipline of modern mycobacteriology. It serves as a resource for understanding the key issues in the epidemiology of tuberculosis and other mycobacterial diseases. Among these issues are disclosing sources of infection, quantifying recent transmission, identifying transmission links, discerning reinfection from relapse, tracking the geographic distribution and clonal expansion of specific strains, and exploring the genetic mechanisms underlying specific phenotypic traits, including virulence, organ tropism, transmissibility, or drug resistance. Since genotyping continues to unravel the biology of mycobacteria, it offers enormous promise in the fight against and prevention of the diseases caused by these pathogens. In this review, molecular typing methods for Mycobacterium tuberculosis and nontuberculous mycobacteria elaborated over the last 2 decades are summarized. The relevance of these methods to the epidemiological investigation, diagnosis, evolution, and control of mycobacterial diseases is discussed.

Whole Genome Sequence Analysis of a Large Isoniazid-Resistant Tuberculosis Outbreak in London: A Retrospective Observational Study

BACKGROUND

A large isoniazid-resistant tuberculosis outbreak centred on London, United Kingdom, has been ongoing since 1995. The aim of this study was to investigate the power and value of whole genome sequencing (WGS) to resolve the transmission network compared to current molecular strain typing approaches, including analysis of intra-host diversity within a specimen, across body sites, and over time, with identification of genetic factors underlying the epidemiological success of this cluster.

METHODS AND FINDINGS

We sequenced 344 outbreak isolates from individual patients collected over 14 y (2 February 1998-22 June 2012). This demonstrated that 96 (27.9%) were indistinguishable, and only one differed from this major clone by more than five single nucleotide polymorphisms (SNPs). The maximum number of SNPs between any pair of isolates was nine SNPs, and the modal distance between isolates was two SNPs. WGS was able to reveal the direction of transmission of tuberculosis in 16 cases within the outbreak (4.7%), including within a multidrug-resistant cluster that carried a rare rpoB mutation associated with rifampicin resistance. Eleven longitudinal pairs of patient pulmonary isolates collected up to 48 mo apart differed from each other by between zero and four SNPs. Extrapulmonary dissemination resulted in acquisition of a SNP in two of five cases. WGS analysis of 27 individual colonies cultured from a single patient specimen revealed ten loci differed amongst them, with a maximum distance between any pair of six SNPs. A limitation of this study, as in previous studies, is that indels and SNPs in repetitive regions were not assessed due to the difficulty in reliably determining this variation.

CONCLUSIONS

Our study suggests that (1) certain paradigms need to be revised, such as the 12 SNP distance as the gold standard upper threshold to identify plausible transmissions; (2) WGS technology is helpful to rule out the possibility of direct transmission when isolates are separated by a substantial number of SNPs; (3) the concept of a transmission chain or network may not be useful in institutional or household settings; (4) the practice of isolating single colonies prior to sequencing is likely to lead to an overestimation of the number of SNPs between cases resulting from direct transmission; and (5) despite appreciable genomic diversity within a host, transmission of tuberculosis rarely results in minority variants becoming dominant. Thus, whilst WGS provided some increased resolution over variable number tandem repeat (VNTR)-based clustering, it was insufficient for inferring transmission in the majority of cases.

Bioinformatics tools and databases for whole genome sequence analysis of Mycobacterium tuberculosis

Tuberculosis (TB) is an infectious disease of global public health importance caused by Mycobacterium tuberculosis complex (MTC) in which M. tuberculosis (Mtb) is the major causative agent. Recent advancements in genomic technologies such as next generation sequencing have enabled high throughput cost-effective generation of whole genome sequence information from Mtb clinical isolates, providing new insights into the evolution, genomic diversity and transmission of the Mtb bacteria, including molecular mechanisms of antibiotic resistance. The large volume of sequencing data generated however necessitated effective and efficient management, storage, analysis and visualization of the data and results through development of novel and customized bioinformatics software tools and databases. In this review, we aim to provide a comprehensive survey of the current freely available bioinformatics software tools and publicly accessible databases for genomic analysis of Mtb for identifying disease transmission in molecular epidemiology and in rapid determination of the antibiotic profiles of clinical isolates for prompt and optimal patient treatment.

Whole-Genome Sequencing Analysis of Serially Isolated Multi-Drug and Extensively Drug Resistant Mycobacterium tuberculosis from Thai Patients

Multi-drug and extensively drug-resistant tuberculosis (MDR and XDR-TB) are problems that threaten public health worldwide. Only some genetic markers associated with drug-resistant TB are known. Whole-genome sequencing (WGS) is a promising tool for distinguishing between re-infection and persistent infection in isolates taken at different times from a single patient, but has not yet been applied in MDR and XDR-TB. We aim to detect genetic markers associated with drug resistance and distinguish between reinfection and persistent infection from MDR and XDR-TB patients based on WGS analysis. Samples of Mycobacterium tuberculosis (n = 7), serially isolated from 2 MDR cases and 1 XDR-TB case, were retrieved from Siriraj Hospital, Bangkok. The WGS analysis used an Illumina Miseq sequencer. In cases of persistent infection, MDR-TB isolates differed at an average of 2 SNPs across the span of 2–9 months whereas in the case of reinfection, isolates differed at 61 SNPs across 2 years. Known genetic markers associated with resistance were detected from strains susceptible to streptomycin (2/7 isolates), p-aminosalicylic acid (3/7 isolates) and fluoroquinolone drugs. Among fluoroquinolone drugs, ofloxacin had the highest phenotype-genotype concordance (6/7 isolates), whereas gatifloxcain had the lowest (3/7 isolates). A putative candidate SNP in Rv2477c associated with kanamycin and amikacin resistance was suggested for further validation. WGS provided comprehensive results regarding molecular epidemiology, distinguishing between persistent infection and reinfection in M/XDR-TB and potentially can be used for detection of novel mutations associated with drug resistance.

Spoligotyping of Mycobacterium tuberculosis Complex Isolates by Use of Ligation-Based Amplification and Melting Curve Analysis

We report here a ligation-based spoligotyping that can identify unamplified spacers in membrane-based spoligotyping due to asymmetric insertion of IS6110 in the direct repeat locus. Our typing yielded 84.4% (411/487) concordance with traditional typing and 100% (487/487) accuracy when confirmed by DNA sequencing.

Whole genome analysis of Mycobacterium tuberculosis isolates from recurrent episodes of tuberculosis, Finland, 1995-2013

Recurrent tuberculosis (TB) is caused by an endogenous re-activation of the same strain of Mycobacterium tuberculosis (relapse) or exogenous infection with a new strain (re-infection). Recurrence of TB in Finland was analysed in a population-based, 19-year study, and genotyping was used to define relapse and re-infection. The M. tuberculosis isolates from patients with suspected relapse were further analysed by whole genome sequencing (WGS) to determine the number and type of mutations occurring in the bacterial genome between the first and second disease episodes. In addition, publicly available tools (PhyResSE and SpolPred) were used to predict drug resistance and spoligotype profile from the WGS data. Of the 8299 notified TB cases, 48 (0.6%) patients had episodes classified as recurrent. Forty-two patients had more than one culture-confirmed TB episode, and isolates from two episodes in 21 patients were available for genotyping. In 18 patients, the M. tuberculosis isolates obtained from the first and second TB episodes had identical spoligotypes. The WGS analysis of the 36 M. tuberculosis isolates from the 18 suspected relapse patients (average time between isolates 2.8 years) revealed 0 to 38 single nucleotide polymorphisms (median 1, mean 3.78) between the first and second isolate. There seemed to be no direct relation between the number of years between the two isolates, or treatment outcome, and the number of single nucleotide polymorphisms. The results suggest that the mutation rate may depend on multiple host-, strain- and treatment-related factors.