[Characterization of a Rif-R population of Bacillus anthracis].

Formation of spontaneous RifR mutants was detected in the populations of various strains of Bacillus anthracis (STI-1, Sterne and CH-7) at a rate of 10(-8) per 1 CFU. The levels of the rifampicin resistance in the mutants were different, the MIC ranged from 16 to 512 micrograms/ml. The clones of the RifR population of the virulent strain CH-7 were heterogeneous in the morphological properties of the colonies and cells, the capacity for the synthesis of the toxin and capsule, the sporulation and virulence. The heterogeneity did not correlate with the levels of the antibiotic resistance. Among the clones of the RifR population there were detected deletion variants by the capacity for the synthesis of the toxin and capsule along with the complete ones. The rifampicin therapy of the infection caused by the complete clone was not efficient. The RifR mutation in B. anthracis did not result in cross resistance to penicillins, cephalosporins, tetracyclines, aminoglycosides, macrolides and chloramphenicol.