Unexpected genomic relationships between Bacillus anthracis strains from Bangladesh and Central Europe

Animal, human, and environmental perspectives on anthrax in Bangladesh

Background

In Bangladesh, the zoonotic transmission of anthrax from animals to humans poses substantial challenges for prevention and control programs, especially in resource-constrained settings. A comprehensive literature review was conducted focusing on anthrax infections in animals, humans, and the environment to enable better design of prevention and control strategies.

Materials and methods

We followed PRISMA guidelines to collect data on anthrax infection in animals and humans from reports between 1980 and January 2023. We used a standardized data extraction template to collect data on study location, year, hosts, deaths and risk factors responsible for anthrax occurrences at the animal, human and environmental sectors. Subsequently, we conducted a thorough analysis of the data gathered to identify the factors responsible for anthrax occurrences and to propose updated strategies for anthrax prevention and control.

Results

Of the 27 articles analyzed, 20 focused on animal or human anthrax, while seven addressed environmental contaminations. A total of 6354 cases of anthrax infection in animals were recorded, with 998 fatalities and an overall case fatality of 15.7 %. In humans, inadequate knowledge about anthrax and its transmission was a significant factor. Risk factors for human cutaneous anthrax included activities such as slaughtering diseased animals and contact with contaminated raw meat or blood. Risky practices such as disposal of animal carcasses in floodwaters or water bodies were observed in some areas, contributing to the persistence of the anthrax pathogen in the environment.

Conclusions

Our study highlights the necessity of a multisectoral One Health approach to effectively control and prevent anthrax outbreaks in both animals and humans. This approach should include comprehensive vaccination programs, social and behavioral change activities, environmental management, and the establishment of surveillance systems. Implementing these recommendations will be crucial in addressing the complex challenges posed by anthrax in low-resource settings.

A classification framework for Bacillus anthracis defined by global genomic structure

Bacillus anthracis, the causative agent of anthrax, is a considerable global health threat affecting wildlife, livestock, and the general public. In this study, whole-genome sequence analysis of over 350 B. anthracis isolates was used to establish a new high-resolution global genotyping framework that is both biogeographically informative and compatible with multiple genomic assays. The data presented in this study shed new light on the diverse global dissemination of this species and indicate that many lineages may be uniquely suited to the geographic regions in which they are found. In addition, we demonstrate that plasmid genomic structure for this species is largely consistent with chromosomal population structure, suggesting vertical inheritance in this bacterium has contributed to its evolutionary persistence. This classification methodology is the first based on population genomic structure for this species and has potential use for local and broader institutions seeking to understand both disease outbreak origins and recent introductions. In addition, we provide access to a newly developed genotyping script as well as the full whole-genome sequence analyses output for this study, allowing future studies to rapidly employ and append their data in the context of this global collection. This framework may act as a powerful tool for public health agencies, wildlife disease laboratories, and researchers seeking to utilize and expand this classification scheme for further investigations into B. anthracis evolution.

Genotyping and phylogenetic location of one clinical isolate of Bacillus anthracis isolated from a human in Russia

Background

Anthrax is a zoonotic disease caused by the Gram-positive bacterium Bacillus anthracis. In Russia, there are more than 35 thousand anthrax stationary unfavourable sites. At the same time, there is very little published information about the isolates of B. anthracis from the territory of Russia. In this study, we report the use of whole genome sequencing (WGS) and bioinformatics analysis to characterize B. anthracis 81/1 strain isolated in Russia in 1969 from a person during an outbreak of the disease in the Stavropol region.

Results

We used 232 B. anthracis genomes, which are currently available in the GenBank database, to determine the place of the Russian isolate in the global phylogeny of B. anthracis. The studied strain was characterized by PCR-based genetic methods, such as Multiple-Locus Variable-Number Tandem Repeat Analysis (MLVA), canonical single nucleotide polymorphisms (canSNP), as well as the method of full-genomic analysis of nucleotide polymorphisms (wgSNP). The results indicate that the Russian B. anthracis 81/1 strain belongs to Trans-Eurasion (TEA) group, the most representative in the world.

Conclusions

In this study, the full genomic sequence of virulent B. anthracis strain from Russia was characterized for the first time. As a result of complex phylogenetic analysis, the place of this isolate was determined in the global phylogenetic structure of the B. anthracis population, expanding our knowledge of anthrax phylogeography in Russia.

Electronic supplementary material

The online version of this article (10.1186/s12866-019-1542-3) contains supplementary material, which is available to authorized users.

Genotyping and phylogenetic placement of Bacillus anthracis isolates from Finland, a country with rare anthrax cases

Background

Anthrax, the zoonotic disease caused by the gram-positive bacterium Bacillus anthracis, is nowadays rare in northern parts of Europe including Finland and Scandinavia. Only two minor outbreaks of anthrax in 1988 and in 2004 and one sporadic infection in 2008 have been detected in animals in Finland since the 1970’s. Here, we report on two Finnish B. anthracis strains that were isolated from spleen and liver of a diseased calf related to the outbreak in 1988 (strain HKI4363/88) and from a local scrotum and testicle infection of a bull in 2008 (strain BA2968). These infections occurred in two rural Finnish regions, i.e., Ostrobothnia in western Finland and Päijänne Tavastia in southern Finland, respectively.

Results

The isolates were genetically characterized by PCR-based methods such as multilocus variable number of tandem repeat analysis (MLVA) and whole genome-sequence analysis (WGS). Phylogenetic comparison of the two strains HKI4363/88 and BA2968 by chromosomal single nucleotide polymorphism (SNP) analysis grouped these organisms within their relatives of the minor canonical A-branch canSNP-group A.Br.003/004 (A.Br.V770) or canonical B-branch B.Br.001/002, respectively. Strain HKI4363/88 clustered relatively closely with other members of the A.Br.003/004 lineage from Europe, South Africa, and South America. In contrast, strain BA2968 clearly constituted a new sublineage within B.Br.001/002 with its closest relative being HYO01 from South Korea.

Conclusions

Our results suggest that Finland harbors both unique (autochthonous) and more widely distributed, common clades of B. anthracis. We suspect that members of the common clades such as strains HKI4363/88 have been introduced only recently by anthropogenic activities involving importation of contaminated animal products. On the other hand, autochthonous strains such as isolate BA2968 probably have an older history of their introduction into Finland as evidenced by a high number of single nucleotide variant sites in their genomes.

Electronic supplementary material

The online version of this article (10.1186/s12866-018-1250-4) contains supplementary material, which is available to authorized users.

Pathogenicity, population genetics and dissemination of Bacillus anthracis

Bacillus anthracis, the etiological agent of anthrax, procures its particular virulence by a capsule and two AB type toxins: the lethal factor LF and the edema factor EF. These toxins primarily disable immune cells. Both toxins are translocated to the host cell by the adhesin-internalin subunit called protective antigen PA. PA enables LF to reach intra-luminal vesicles, where it remains active for long periods. Subsequently, LF translocates to non-infected cells, leading to inefficient late therapy of anthrax. B. anthracis undergoes slow evolution because it alternates between vegetative and long spore phases. Full genome sequence analysis of a large number of worldwide strains resulted in a robust evolutionary reconstruction of this bacterium, showing that B. anthracis is split in three main clades: A, B and C. Clade A efficiently disseminated worldwide underpinned by human activities including heavy intercontinental trade of goat and sheep hair. Subclade A.Br.WNA, which is widespread in the Northern American continent, is estimated to have split from clade A reaching the Northern American continent in the late Pleistocene epoch via the former Bering Land Bridge and further spread from Northwest southwards. An alternative hypothesis is that subclade A.Br.WNA. evolved from clade A.Br.TEA tracing it back to strains from Northern France that were assumingly dispatched by European explorers that settled along the St. Lawrence River. Clade B established mostly in Europe along the alpine axis where it evolved in association with local cattle breeds and hence displays specific geographic subclusters. Sequencing technologies are also used for forensic applications to trace unintended or criminal acts of release of B. anthracis. Under natural conditions, B. anthracis generally affects domesticated and wild ruminants in arid ecosystems. The more recently discovered B. cereus biovar anthracis spreads in tropical forests, where it threatens particularly endangered primate populations.