[The isolation of capsule-free variants of Francisella tularensis].

New methods (selection in medium T with 20% Tween-80, inducing mutations leading to the appearance of resistance to triphenyl tetrazolium chloride or indoxyl phosphate) helped create a collection of F. tularensis stable non-capsular variants from strains of different subspecies. The characteristic features of all F. tularensis cap- variants include inability to serologic tests with erythrocytic diagnosticum, the absence of capsular antigens, sensitivity to normal human serum.