Genetic characteristics of Bacillus anthracis isolated from northwestern China from 1990 to 2016

Epidemiological Characteristics of Human Anthrax - China, 2018-2021

Introduction

The epidemic of human anthrax is at a low level in China in recent years, but the reported incidence increased in 2021. In order to understand the current landscape of research and knowledge about anthrax in China, the epidemiological characteristics of anthrax in humans from 2018 to 2021 were analyzed and the prevention and control suggestions were proposed.

Methods

Surveillance data of anthrax in humans and livestock, together with human outbreaks data during 2018-2021, were collected and analyzed by descriptive statistics methods. The number and proportion of outbreaks, cases and deaths by provincial-level administrative divisions (PLADs), clinical types, and contributing factors were calculated.

Results

A total of 1,244 cases of human anthrax and 53 outbreaks were reported from 2018 to 2021 in China. While the incidence of anthrax declined from 2018 to 2020, it increased in 2021. The regions of anthrax were mainly located in the west and the northeast PLADs of China, though cases were reported in some central and eastern PLADs in 2021. Young and middle-aged men involved in animal husbandry were found to be at a higher risk of anthrax. All the reported outbreaks were associated with the exposure of infected livestock. A total of 296 livestock anthrax cases were reported.

Conclusions

The increased incidence and wider geographical distribution of human anthrax in 2021 were found to be the result of inadequate supervision of diseased animals as well as updated diagnostic criteria. As such, the monitoring of risk factors and emergency preparation procedures should be strengthened at the national level. In addition, it is also critical to strengthen health education for high-risk occupational groups and strengthen professional training for local clinicians. Finally, more measures should be carried out to strengthen anthrax surveillance in livestock husbandry.

Identification of the molecular characteristics of Bacillus anthracis (1982-2020) isolates in East Indonesia using multilocus variable-number tandem repeat analysis

Background and Aim:

Anthrax is one of the endemic strategic diseases in East Indonesia, particularly in the provinces of South Sulawesi, West Sulawesi, Gorontalo, East Nusa Tenggara, and West Nusa Tenggara. Anthrax is an important disease due to its zoonotic and economic impact on the livestock industry. This study aimed to identify the molecular characteristics of Bacillus anthracis in East Indonesia using multilocus variable-number tandem repeat (VNTR) analysis (MLVA).

Materials and Methods:

Isolates were obtained from an investigation of anthrax outbreaks in five provinces of East Indonesia from 1982 to 2020. Conventional polymerase chain reaction for B. anthracis was used to identify MLVA-8. Deoxyribonucleic acid sequencing analysis was based on MLVA-8 primers for VNTR identification of the phylogenetic relationship among 24 isolates of B. anthracis obtained from 17 distinct districts/cities in East Indonesia. Tandem Repeats Finder was used for VNTR identification, and Molecular Evolutionary Genetics Analysis X was used to construct phylogenetic analysis.

Results:

In this study, 24 isolates were classified as genotype or lineage A. There were four subgroups of B. anthracis circulating in East Indonesia based on eight molecular marker loci sequence results.

Conclusion:

The findings of this study show that MLVA-8 typing might be useful as a subtyping tool for the epidemiological investigation of identical genotypes and low genetic diversity of B. anthracis. No other lineage of B. anthracis was circulating in East Indonesia. Other molecular methods are needed, such as extended MLVA, whole-genome sequencing, and canonical single-nucleotide polymorphism, for a more precise study of B. anthracis genetic diversity.

Phylogenetics of Bacillus anthracis isolates from Russia and bordering countries

Anthrax is a concern for public health and veterinary medicine in Russia. The available phylogenetic data on isolates from Russia and neighboring CIS countries are clearly not enough to gain a better understanding of their position in the global phylogenetic population structure of this pathogen. In this study, we analyzed the genomes of 66 Bacillus anthracis strains, which were isolated between 1935 and 2019 from different sources in Russia, as well as in Ukraine, Azerbaijan, Georgia, Armenia and Moldova. Whole genome SNP analysis of genomes of 66 strains obtained in this study along with 222 B. anthracis genomes available in the GenBank database revealed 7242 SNPs used to construct a phylogenetic reconstruction with the method of Maximum Likelihood. Studied strains belong to 6 different genetic groups: A.Br.008(A.Br.008/009), A.Br.081(Ames), A.Br.014(A.Br.Aust94), A.Br.082(A.Br.001/002), A.Br.034(A.Br.005/006, Ancient A) and B.Br.002 (B.Br.001/002). Within the group A.Br.014(A.Br.Aust94) a subcluster A.Br.029 of strains isolated in Georgia, Armenia, Azerbaijan, Russia (Republic of Dagestan) and Turkey, named Caucasus-East Anatolia (CEA), was identified. In the subgroup A.Br.105(Tsiankovskii) the cluster A.Br.117 of strains from Russia, Ukraine and Slovakia are assigned, in the subgroup A.Br118 (STI) - cluster A.Br.123 with strains from Russia and Georgia and cluster A.Br.125 with strains from Republic of Dagestan. New subclusters B.Br.017("EUROPE") were identified in the B.Br.002(B.Br.001/002) cluster, represented by strains from the European part of Russia, as well as from South Korea and Finland. For 8 clusters and subclusters, the SNP markers were identified. The study confirmed a significant genetic diversity of the strains isolated in Russia and border countries and clarified their position in the phylogenetic structure of the global B. anthracis population. New genetic clusters A.Br.029 (CEA), A.Br.117, A.Br.123, A.Br.125, and B.Br.017 («EUROPE») were defined. 96 marker SNPs specific for these clusters were identified.

Changed epidemiology of anthrax and molecular characteristics of Bacillus anthracis in Inner Mongolia Autonomous Region, China

Anthrax is a natural foci disease in Inner Mongolia, which poses a severe threat to public health. In this study, the incidence number, rate and constituent ratio were used to describe the epidemiological characteristics of anthrax in the region from 1956-2018. The molecular correlation and genetic characteristics of the strains were investigated using canonical single nucleotide polymorphisms (CanSNP), multiple-locus variable-number tandem repeat analysis (MLVA-15) and whole genome sequencing (WGS). The epidemiological characteristics of anthrax in Inner Mongolia have altered significantly. The incidence of anthrax has decreased annually without vaccination, and the regional distribution of anthrax gradually transferred from central and western regions to the eastern. Moreover, the occupation distribution evolved from multiple early occupations to predominated by farmers and herdsmen. This change is closely related to policy factors and to changes in the means of production and the living habits of the local population. This indicates that reformulating the control and prevention strategies is essential. Both A. Br. Ames and A. Br. 001/002 subgroups were the predominant CanSNP genotypes of Bacillus anthracis in Inner Mongolia. A total of 36 strains constituted six shared MLVA-15 genotypes, suggesting an epidemiological link between the strains of each shared genotype. The six shared genotypes ([GT1, 9, 11 and 15] and [GT8 and 12]) consisting of 2-7 strains confirmed the occurrence of multiple point outbreaks and cross-regional transmission caused by multiple common sources of infection. Phylogenetic analysis based on the WGS core genome showed that strains from this study formed an independent clade (C.V.), and they were positioned close to each other, suggesting a common origin. Further comparison analysis should be performed to ascertain the geographic origin of these strains.

Genetic Diversity of Australian Bacillus anthracis Isolates Revealed by Multiple-Locus Variable-Number Tandem Repeat Analysis

Outbreaks of anthrax occur sporadically in Australia and most commonly in the "anthrax belt", a region which extends from southern Queensland through the centre of New South Wales and into northern Victoria. Little is known about the epidemiological links between Bacillus anthracis isolates taken from different outbreaks and the diversity of strains within Australia. We used multiple-locus variable-number tandem repeat analysis employing 25 markers (MLVA25) to genotype 99 B. anthracis isolates from an archival collection of Australian isolates. MLVA25 genotyping revealed eight unique genotypes which clustered within the previously defined A3 genotype of B. anthracis. Genotyping of B. anthracis strains from outbreaks of disease in Victoria identified the presence of multiple genotypes associated with these outbreaks. The geographical distribution of genotypes within Australia suggests that a single genotype was introduced into the eastern states of Australia, followed by the spread and localised differentiation of the pathogen (MLVA25 genotypes MG1-MG6) throughout the anthrax belt. In contrast, unexplained occurrences of disease in areas outside of this anthrax belt which are associated with different genotypes, (MLVA25 genotypes MG7 and MG8) indicate separate introductions of B. anthracis into Australia.

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.

Genetic diversity of Bacillus anthracis Ames lineage strains in China

BACKGROUND

Anthrax is an endemic disease that persists in the rural regions of China. The global genetic population structure of B.anthracis has also been defined by the canonical single-nucleotide polymorphisms (canSNP) and multiple-locus variable-number tandem repeat analysis (MLVA). Five canSNP lineages were found in China, and the A.Br.Ames lineage has been the second predominant group in recent years in China. The objective of this study was to reveal genetic diversity of the Ames lineage strains by MLVA.

METHODS

Two molecular typing methods, canSNP and MLVA with 15markers were used to study the genetic relationship among the Ames lineage strains. The outbreak information associated with these strains was also collected and investigated.

RESULTS

From 2007 to 2018, a total of 21 human anthrax infection outbreaks (68 patients) associated with B. anthracis Ames lineage strains were reported in China. Ames lineage strain-associated human anthrax is mainly distributed in the northern part of China, including the provinces of Inner Mongolia, Liaoning, Gansu, and Xinjiang. In the study, a total of 30 Ames lineage strains were included and 10 MLVA15 genotypes were identified. These strains were mainly found in northeast China, Inner Mongolia and Liaoning. In recent years, the Ames lineage strains were isolated in the two provinces every year. The 18 Ames lineage strains isolated from Inner Mongolia were divided into eight MLVA15 genotypes. From 2010 to 2015, there were continuous reports of outbreaks in Keyouzhongqi County, Inner Mongolia, and the strains that were isolated annually in succession belonged to the MLVA15-30 genotype.

CONCLUSIONS

The Ames lineage strains are widely distributed in northern China. Their genetic diversity can be illustrated by the results of the MLVA. The genetic characteristics of the Ames lineage strains from outbreaks in different provinces varied. In some areas, human anthrax outbreaks occurred annually in succession, and these related strains grouped together. These observations indicate that the local environment was persistently contaminated with B. anthracis spores, vaccination of livestock should become the fundamental control measure in the areas.