Bacillus anthracis in China and its relationship to worldwide lineages

Abstract

BackgroundThe global pattern of distribution of 1033 B. anthracis isolates has previously been defined by a set of 12 conserved canonical single nucleotide polymorphisms (canSNP). These studies reinforced the presence of three major lineages and 12 sub-lineages and sub-groups of this anthrax-causing pathogen. Isolates that form the A lineage (unlike the B and C lineages) have become widely dispersed throughout the world and form the basis for the geographical disposition of "modern" anthrax. An archival collection of 191 different B. anthracis isolates from China provides a glimpse into the possible role of Chinese trade and commerce in the spread of certain sub-lineages of this pathogen. Canonical single nucleotide polymorphism (canSNP) and multiple locus VNTR analysis (MLVA) typing has been used to examine this archival collection of isolates.ResultsThe canSNP study indicates that there are 5 different sub-lineages/sub-groups in China out of 12 previously described world-wide canSNP genotypes. Three of these canSNP genotypes were only found in the western-most province of China, Xinjiang. These genotypes were A.Br.008/009, a sub-group that is spread across most of Europe and Asia; A.Br.Aust 94, a sub-lineage that is present in Europe and India, and A.Br.Vollum, a lineage that is also present in Europe. The remaining two canSNP genotypes are spread across the whole of China and belong to sub-group A.Br.001/002 and the A.Br.Ames sub-lineage, two closely related genotypes. MLVA typing adds resolution to the isolates in each canSNP genotype and diversity indices for the A.Br.008/009 and A.Br.001/002 sub-groups suggest that these represent older and established clades in China.ConclusionB. anthracis isolates were recovered from three canSNP sub-groups (A.Br.008/009, A.Br.Aust94, and A.Br.Vollum) in the western most portion of the large Chinese province of Xinjiang. The city of Kashi in this province appears to have served as a crossroads for not only trade but the movement of diseases such as anthrax along the ancient "silk road". Phylogenetic inference also suggests that the A.Br.Ames sub-lineage, first identified in the original Ames strain isolated from Jim Hogg County, TX, is descended from the A.Br.001/002 sub-group that has a major presence in most of China. These results suggest a genetic discontinuity between the younger Ames sub-lineage in Texas and the large Western North American sub-lineage spread across central Canada and the Dakotas.

Characterization of Genetic Diversity of Bacillus anthracis in France by Using High-Resolution Melting Assays and Multilocus Variable-Number Tandem-Repeat Analysis

“…It may be of interest to note that these zones, close to the mountainous massifs of France, share similar land topologies, made of pastoral valleys. Our data, consistent with other MLVA studies reporting new additional genotypes among Italian, Polish, and Swiss isolates (7)(8)(9)26) (33). The strains found in Europe (36,38) may represent old imported infections from Asia via animals or human activities, such as trading (33).…”

“…This leads to a genotyping method that uses a set of 13 strategically placed canSNPs to subdivide B. anthracis isolates into three recognized major lineages (A, B, and C), with further subdivision into 12 clonal sublineages or subgroups (36). This method had been applied to analyze several collections of B. anthracis strains of worldwide origin (2,7,23,26,33,36). However, as it is based on TaqMan minor groove binding allelic discrimination assays, the current method incurs a high cost per studied marker.…”

Genome-Wide Single Nucleotide Polymorphism Typing Method for Identification of Bacillus anthracis Species and Strains among B. cereus Group Species

“…Testing methods using MLVA 25 (13) or canSNPs in combination with MLVA 15 (23,25) have been reported as rapid strain genotyping systems for B. anthracis; however, the MLVA method is complicated given the need to estimate the correct number of repeat units. Indeed, we have experienced that the observed length of fragments obtained using MLVA 25 must be normalized into their actual length by DNA sequencing every time the assay is performed (16).…”

TheBacillus anthracisGenome

“…One place where B. anthracis strains of different provenance seem to have encountered each other is Texas, where the Ames strain was originally isolated. Ames itself may have its recent origins in China and may have been shipped to East Texas, rather than pre -Columbian importation from Russia (Simonson et al, 2009 ).…”