Diversity of Bacillus anthracis strains in Georgia and of vaccine strains from the former Soviet Union

Despite the increased number of anthrax outbreaks in Georgia and the other Caucasian republics of the former Soviet Union, no data are available on the diversity of the Bacillus anthracis strains involved. There is also little data available on strains from the former Soviet Union, including the strains previously used for vaccine preparation. In this study we used eight-locus variable-number tandem repeat analyses to genotype 18 strains isolated from infected animals and humans at different sites across Georgia, where anthrax outbreaks have occurred in the last 10 years, and 5 strains widely used for preparation of human and veterinary vaccines in the former Soviet Union. Three different genotypes affiliated with the A3.a cluster were detected for the Georgian isolates. Two genotypes were previously shown to include Turkish isolates, indicating that there is a regional strain pattern in the South Caucasian-Turkish region. Four of the vaccine strains were polymorphic, exhibiting three different patterns of the cluster A1.a genotype and the cluster A3.b genotype. The genotype of vaccine strain 71/12, which is considered an attenuated strain in spite of the presence of both of the virulence pXO plasmids, appeared to be a novel genotype in the A1.a cluster.