Improvement of methods for identification of atypical anthrax strains and their differentiation from closely related bacilli | Усовершенствование методов идентификации атипичных штаммов возбудителя сибирской язвы и их дифференциация от близкородственных бацилл

Studied were biological properties of atypical strains (AS) Bacillus anthracis and improved were methods for their identification and differentiation from the group of closely related Bacillus cereus by analyzing 1101 strains of microorganisms isolated in 33 regions of the RF and 6 near border countries and identified as B. anthracis. The occurrence of isolating AS of the anthrax agent in natural conditions and the frequency of misidentification of bacillus strain like B. anthracis were evaluated. The phenotypic test was improved to determine the sensibility of strain to penicillin. Variant of multiplex PCR was developed to differentiate B. anthracis strain with any set of plasmids from closely related bacilli strains. Feasibility of multiple loci analysis of 6 chromosomal and 2 plasmid regions of B. anthracis genome having a variable number of tandem repeats (MLVA) for differentiation of anthrax strains from other bacilli of genus Bacillus was demonstrated. MLVA allows at the same time and very exactly to determine genotype, to differ some atypical B. anthracis strains from typical ones and to differentiate any anthrax strains from other bacilli. It is concluded that the isolation occurrence of B. anthracis AS is equal to that of bacilli misidentified as B. anthracis. According to the final identification of 1101 strains, when 969 strains (88.01%) were B. anthracis, and 132 strains (11.99%) did not correspond to the features of the anthrax agent by the basic tests, laboratory diagnosis of anthrax. In order to optimize the processes of identification of B. anthracis typical and atypical strains and differentiation between closely related bacilli, it is rational to use the disk-diffusion method with commercially available penicillin disks, multiprimer PCR and MLVA method on 6 chromosomal and 2 plasmid loci