Extended multiple-locus variable-number tandem-repeat analysis of Bacillus anthracis strains isolated in Poland

Twenty-one variable-number tandem-repeat (VNTR) marker loci were used for extended multiple locus VNTR analysis (MLVA) of 14 laboratory strains of Bacillus anthracis isolated in Poland and vaccine strain Sterne 34F2A. The extended MLVA (MLVA-21) distinguished six genotypes clustered in three main branches. Monomorphic branch 1 consisted of the vaccine strain and six isolates from distinct samples of a cow died from anthrax. This group also encompassed three haemolytic isolates of B. anthracis. Branches 2 and 3 were heterogeneous and consisted of five and three isolates of the phylogenetic lineages B2 and A1, respectively. MLVA-21 supported thesis on the anthrax agent heterogeneity in Poland. This study brought an additional evidence that haemolytic B. anthracis strains isolated in Poland are closely related to the vaccine strain Stere 34F2 and may together constitute the same sensu stricto strain. No epidemiological link could be however traced between both the vaccine and the haemolytic strains.