Rapid Nanopore Whole-Genome Sequencing for Anthrax Emergency Preparedness

From Spores to Suffering: Understanding the Role of Anthrax in Bioterrorism

INTRODUCTION

Anthrax, caused by the bacterium Bacillus anthracis, stands as a formidable threat with both natural and bioterrorism-related implications. Its ability to afflict a wide range of hosts, including humans and animals, coupled with its potential use as a bioweapon, underscores the critical importance of understanding and advancing our capabilities to combat this infectious disease. In this context, exploring futuristic approaches becomes imperative, as they hold the promise of not only addressing current challenges but also ushering in a new era in anthrax management. This review delves into strategies to mitigate the impact of anthrax on global health and security, envisioning a future where our arsenal against anthrax is characterized by precision and adaptability.

MATERIALS AND METHODS

This article highlights the significant potential of anthrax as a bioweapon, while also highlighting current knowledge and strategies developed against this deadly pathogen. We have performed an extensive research and literature review in concordance with the criteria outlined by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. A search strategy was conducted by using numerous keywords on various academic databases, yielding an initial set of 546 records along with 80 supplementary articles. The search included research papers, review papers, perspectives, clinical guidelines, and scientific blogs. The primary and secondary screening of the articles were conducted by 2 independent reviewers along with a third reviewer mitigating any discrepancies and biases encountered during the process. A set of inclusion and exclusion criteria were formulated, and a PICO framework was adapted based on which multiple records were analyzed and considered for the review.

RESULTS

In total, 53 articles were selected after completing a comprehensive systematic literature review. This review proposes novel approaches and scientific analysis of the complexities surrounding anthrax in the context of bioterrorism, highlighting the emerging technologies and strategies employed for bioterrorism mitigation.

CONCLUSIONS

The upcoming advancements in anthrax research will be based on cutting-edge technologies and innovative approaches that demonstrate great potential for prevention, detection, and treatment. These advancements may include the incorporation of synthetic biology techniques such as precise manipulation of biological components, nanoscale diagnostics, and Clustered regularly interspaced short palindromic repeats-based technologies, which could revolutionize our ability to combat anthrax on a molecular level. As these progressive methodologies continue to evolve, the integration of these technologies has the potential to redefine our strategies against anthrax, providing more accurate, personalized, and adaptable approaches to address the challenges posed by this infectious threat.

Research progress and application of the third-generation sequencing technologies in forensic medicine

Third-generation sequencing technologies, exemplified by single-molecule real-time sequencing and nanopore sequencing, provide a constellation of advantages, including long read lengths, high throughput, real-time sequencing capabilities, and remarkable portability. These cutting-edge methodologies have provided new tools for genomic analysis in forensic medicine. To gain a comprehensive understanding of the current applications and cutting-edge trends of third-generation sequencing technologies in forensic medicine, this study retrieved relevant literature from the China National Knowledge Infrastructure (CNKI) database and the Web of Science (WOS) database. Using bibliometric software CiteSpace 6.1.R6, the study visualized publication volume, countries, and keywords related to the application of third-generation sequencing technologies in forensic medicine from 2014 to 2023. The review then summarized the foundational principles, characteristics, and promising prospects of third-generation sequencing technologies in forensic medicine. Notably, it highlights their remarkable contributions in forensic individual identification, body fluid identification, forensic epigenetic analysis, microbial analysis and forensic species identification.

Molecular characterization of an outbreak-involved Bacillus anthracis strain confirms the spillover of anthrax from West Africa

BACKGROUND

Anthrax, a zoonotic disease caused by the spore-forming bacterium Bacillus anthracis, remains a major global public health concern, especially in countries with limited resources. Sierra Leone, a West African country historically plagued by anthrax, has almost been out of report on this disease in recent decades. In this study, we described a large-scale anthrax outbreak affecting both animals and humans and attempted to characterize the pathogen using molecular techniques.

METHODS

The causative agent of the animal outbreak in Port Loko District, Sierra Leone, between March and May 2022 was identified using the nanopore sequencing technique. A nationwide active surveillance was implemented from May 2022 to June 2023 to monitor the occurrence of anthrax-specific symptoms in humans. Suspected cases were subsequently verified using quantitative polymerase chain reaction. Full-genome sequencing was accomplished by combining long-read and short-read sequencing methods. Subsequent phylogenetic analysis was performed based on the full-chromosome single nucleotide polymorphisms.

RESULTS

The outbreak in Port Loko District, Sierra Leone, led to the death of 233 animals between March 26th and May 16th, 2022. We ruled out the initial suspicion of Anaplasma species and successfully identified B. anthracis as the causative agent of the outbreak. As a result of the government's prompt response, out of the 49 suspected human cases identified during the one-year active surveillance, only 6 human cases tested positive, all within the first month after the official declaration of the outbreak. The phylogenetic analysis indicated that the BaSL2022 isolate responsible for the outbreak was positioned in the A.Br.153 clade within the TransEuroAsian group of B. anthracis.

CONCLUSIONS

We successfully identified a large-scale anthrax outbreak in Sierra Leone. The causative isolate of B. anthracis, BaSL2022, phylogenetically bridged other lineages in A.Br.153 clade and neighboring genetic groups, A.Br.144 and A.Br.148, eventually confirming the spillover of anthrax from West Africa. Given the wide dissemination of B. anthracis spores, it is highly advisable to effectively monitor the potential reoccurrence of anthrax outbreaks and to launch campaigns to improve public awareness regarding anthrax in Sierra Leone.

Comparison of Illumina and Oxford Nanopore Technology for genome analysis of Francisella tularensis, Bacillus anthracis, and Brucella suis

BACKGROUND

Bacterial epidemiology needs to understand the spread and dissemination of strains in a One Health context. This is important for highly pathogenic bacteria such as Bacillus anthracis, Brucella species, and Francisella tularensis. Whole genome sequencing (WGS) has paved the way for genetic marker detection and high-resolution genotyping. While such tasks are established for Illumina short-read sequencing, Oxford Nanopore Technology (ONT) long-read sequencing has yet to be evaluated for such highly pathogenic bacteria with little genomic variations between strains. In this study, three independent sequencing runs were performed using Illumina, ONT flow cell version 9.4.1, and 10.4 for six strains of each of Ba. anthracis, Br. suis and F. tularensis. Data from ONT sequencing alone, Illumina sequencing alone and two hybrid assembly approaches were compared.

RESULTS

As previously shown, ONT produces ultra-long reads, while Illumina produces short reads with higher sequencing accuracy. Flow cell version 10.4 improved sequencing accuracy over version 9.4.1. The correct (sub-)species were inferred from all tested technologies, individually. Moreover, the sets of genetic markers for virulence, were almost identical for the respective species. The long reads of ONT allowed to assemble not only chromosomes of all species to near closure, but also virulence plasmids of Ba. anthracis. Assemblies based on nanopore data alone, Illumina data alone, and both hybrid assemblies correctly detected canonical (sub-)clades for Ba. anthracis and F. tularensis as well as multilocus sequence types for Br. suis. For F. tularensis, high-resolution genotyping using core-genome MLST (cgMLST) and core-genome Single-Nucleotide-Polymorphism (cgSNP) typing produced highly comparable results between data from Illumina and both ONT flow cell versions. For Ba. anthracis, only data from flow cell version 10.4 produced similar results to Illumina for both high-resolution typing methods. However, for Br. suis, high-resolution genotyping yielded larger differences comparing Illumina data to data from both ONT flow cell versions.

CONCLUSIONS

In summary, combining data from ONT and Illumina for high-resolution genotyping might be feasible for F. tularensis and Ba. anthracis, but not yet for Br. suis. The ongoing improvement of nanopore technology and subsequent data analysis may facilitate high-resolution genotyping for all bacteria with highly stable genomes in future.

Portable nanopore-sequencing technology: Trends in development and applications

Sequencing technology is the most commonly used technology in molecular biology research and an essential pillar for the development and applications of molecular biology. Since 1977, when the first generation of sequencing technology opened the door to interpreting the genetic code, sequencing technology has been developing for three generations. It has applications in all aspects of life and scientific research, such as disease diagnosis, drug target discovery, pathological research, species protection, and SARS-CoV-2 detection. However, the first- and second-generation sequencing technology relied on fluorescence detection systems and DNA polymerization enzyme systems, which increased the cost of sequencing technology and limited its scope of applications. The third-generation sequencing technology performs PCR-free and single-molecule sequencing, but it still depends on the fluorescence detection device. To break through these limitations, researchers have made arduous efforts to develop a new advanced portable sequencing technology represented by nanopore sequencing. Nanopore technology has the advantages of small size and convenient portability, independent of biochemical reagents, and direct reading using physical methods. This paper reviews the research and development process of nanopore sequencing technology (NST) from the laboratory to commercially viable tools; discusses the main types of nanopore sequencing technologies and their various applications in solving a wide range of real-world problems. In addition, the paper collates the analysis tools necessary for performing different processing tasks in nanopore sequencing. Finally, we highlight the challenges of NST and its future research and application directions.

Sequence-based detection and typing procedures for Burkholderia mallei: Assessment and prospects

Although glanders has been eradicated in most of the developed world, the disease still persists in various countries such as Brazil, India, Pakistan, Bangladesh, Nepal, Iran, Bahrain, UAE and Turkey. It is one of the notifiable diseases listed by the World Organization for Animal Health. Occurrence of glanders imposes restriction on equestrian events and restricts equine movement, thus causing economic losses to equine industry. The genetic diversity and global distribution of the causing agent, Burkholderia (B.) mallei, have not been assessed in detail and are complicated by the high clonality of this organism. Among the identification and typing methods, PCR-based methods for distinguishing B. mallei from its close relative B. pseudomallei as well as genotyping using tandem repeat regions (MLVA) are established. The advent and continuous advancement of the sequencing techniques and the reconstruction of closed genomes enable the development of genome guided epidemiological tools. For achieving a higher genomic resolution, genotyping methods based on whole genome sequencing data can be employed, like genome-wide single nucleotide polymorphisms. One of the limitations in obtaining complete genomic sequences for further molecular characterization of B. mallei is its high GC content. In this review, we aim to provide an overview of the widely used detection and typing methods for B. mallei and illustrate gaps that still require development. The genomic features of Burkholderia, their high homology and clonality will be first described from a comparative genomics perspective. Then, the commonly used molecular detection (PCR systems) and typing systems (e.g., multilocus sequence typing, variable number of tandem repeat analysis) will be presented and put in perspective with recently developed genomic methods. Also, the increasing availability of B. mallei genomic sequences and evolution of the sequencing methods offers exciting prospects for further refinement of B. mallei typing, that could overcome the difficulties presently encountered with this particular bacterium.

Subtyping Evaluation of Salmonella Enteritidis Using Single Nucleotide Polymorphism and Core Genome Multilocus Sequence Typing with Nanopore Reads

Whole-genome sequencing (WGS) for public health surveillance and epidemiological investigation of foodborne pathogens predominantly relies on sequencing platforms that generate short reads. Continuous improvement of long-read nanopore sequencing, such as Oxford nanopore technologies (ONT), presents a potential for leveraging multiple advantages of the technology in public health and food industry settings, including rapid turnaround and onsite applicability in addition to superior read length. Using an established cohort of Salmonella Enteritidis isolates for subtyping evaluation, we assessed the technical readiness of nanopore long read sequencing for single nucleotide polymorphism (SNP) analysis and core-genome multilocus sequence typing (cgMLST) of a major foodborne pathogen. By multiplexing three isolates per flow cell, we generated sufficient sequencing depths in <7 h of sequencing for robust subtyping. SNP calls by ONT and Illumina reads were highly concordant despite homopolymer errors in ONT reads (R9.4.1 chemistry). In silico correction of such errors allowed accurate allelic calling for cgMLST and allelic difference measurements to facilitate heuristic detection of outbreak isolates. IMPORTANCE Evaluation, standardization, and implementation of the ONT approach to WGS-based, strain-level subtyping is challenging, in part due to its relatively high base-calling error rates and frequent iterations of sequencing chemistry and bioinformatic analytics. Our study established a baseline for the continuously evolving nanopore technology as a viable solution to high-quality subtyping of Salmonella, delivering comparable subtyping performance when used standalone or together with short-read platforms. This study paves the way for evaluating and optimizing the logistics of implementing the ONT approach for foodborne pathogen surveillance in specific settings.

BugSplit enables genome-resolved metagenomics through highly accurate taxonomic binning of metagenomic assemblies

A large gap remains between sequencing a microbial community and characterizing all of the organisms inside of it. Here we develop a novel method to taxonomically bin metagenomic assemblies through alignment of contigs against a reference database. We show that this workflow, BugSplit, bins metagenome-assembled contigs to species with a 33% absolute improvement in F1-score when compared to alternative tools. We perform nanopore mNGS on patients with COVID-19, and using a reference database predating COVID-19, demonstrate that BugSplit's taxonomic binning enables sensitive and specific detection of a novel coronavirus not possible with other approaches. When applied to nanopore mNGS data from cases of Klebsiella pneumoniae and Neisseria gonorrhoeae infection, BugSplit's taxonomic binning accurately separates pathogen sequences from those of the host and microbiota, and unlocks the possibility of sequence typing, in silico serotyping, and antimicrobial resistance prediction of each organism within a sample. BugSplit is available at https://bugseq.com/academic .

Molecular Typing of Ukrainian Bacillus anthracis Strains by Combining Whole-Genome Sequencing Techniques

Anthrax is a recurrent zoonosis in the Ukraine with outbreaks occurring repeatedly in certain areas. For determining whether several Bacillus anthracis genotypes are circulating in this region, four strains from various sources isolated from different regions of the Ukraine were investigated. By combining long- and short-read next-generation sequencing techniques, highly accurate genomes were reconstructed, enabling detailed in silico genotyping. Thus, the strains could be assigned to the Tsiankovskii subgroup of the “TransEurAsia” clade, which is commonly found in this region. Their high genetic similarity suggests that the four strains are members of the endemic population whose progenitor was once introduced in the Ukraine and bordering regions. This study provides information on B. anthracis strains from a region where there is little knowledge of the local population, thereby adding to the picture of global B. anthracis genotype distribution. We also emphasize the importance of surveillance and prevention methods regarding anthrax outbreaks, as other studies predicted a higher number of cases in the future due to global warming.