IMPROVEMENT OF METHODS FOR IDENTIFICATION OF ATYPICAL ANTHRAX STRAINS AND THEIR DIFFERENTIATION FROM CLOSELY RELATED BACILLI

Aim. To study biologic characteristics of atypical strains of anthrax agent in order to improve methods of identification and differentiation from closely related bacilli. Materials and methods. Objects of the study were 1101 strains of microorganisms of which following were experimentally examined: atypical — 40 strains, typical — 2, saprophytic bacilli from Bacillus genus — 50. Aside from conventional methods, additional tests for intraspecies differentiation as well as multiplex PCR method were used for identification. Results. Isolation rate of atypical strains of anthrax agent in natural conditions as well as frequency of misidentification of bacillary strains as Bacillus anthracis was assessed. Phenotypical test for determination of susceptibility to penicillin was improved. Variant of multiplex PCR for differentiation of B.anthracis strains with any set of plasmids from closely related bacilli strains was developed. Feasibility to use multiple loci analysis of 6 chromosomal and 2 plasmid regions of B.anthracis genome containing variable number of tandem repeats (MLVA) for differentiation of B.anthracis strains from other bacilli from Bacillus genus was demonstrated. Conclusion. 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 disk-diffusion method with commercially available disks of penicillin, multiprimer PCR and MLVA on 6 chromosomal and 2 plasmid loci.

Bacillus anthracis, atypical strains, closely related bacilli, identification, differentiation, loci with variable number of tandem repeats