Molecular diversity of Bacillus anthracis in the Netherlands: Investigating the relationship to the worldwide population using whole-genome SNP discovery

•CanSNP typing of isolates from Dutch anthrax outbreaks was performed.•The phylogenetic diversity is analogous to findings in other European countries.•Phylogenetic relationships with strains from other parts of the world is discussed.•New HRM assays based on diagnostic SNPs were developed for epidemiological purposes.

Bacillus anthracis, the causative agent of anthrax, has been widely described as a clonal species. Here we report the use of both canonical SNP analysis and whole-genome sequencing to characterize the phylogenetic lineages of B. anthracis from the Netherlands. Eleven strains isolated over a 25-years period (1968-1993) were paired-end sequenced using parallel sequencing technology. Five canSNP groups or lineages, i.e. A.Br.001/002 (n = 6), A.Br.Aust94 (n = 2), A.Br.008/011 (n = 1), A.Br.011/009 (n = 1) and A.Br.Vollum (n = 1) were identified. Comparative analyses, with a focus on SNPs discovery, were carried out using a total of 52 B. anthracis genomes. A phylogeographic “Dutch” cluster within the dominant A.Br.001/002 group was discovered, involving isolates from a single outbreak. Diagnostic SNPs specific to the newly identified sub-groups were developed into high-resolution melting SNP discriminative assays for the purpose of rapid molecular epidemiology. Phylogenetic relationships with strains from other parts of the world are discussed.