[The characteristics of the biological properties of capsule-free variants of Francisella tularensis]

Comparative study of the properties of initial capsular (cap+) and non-capsular (cap-) F. tularensis strains has revealed that the non-capsular variants have their specific biological features. The characteristic features of these variants are avirulence and inability to produce an immunogenic effect in sensitive laboratory animals. Cap- mutants, depending on the method of their obtaining, may exhibit different sensitivity to some antibacterial preparations. In contrast to the initial virulent strains, cap- variants are intensively phagocytosed by peritoneal macrophages of white mice and capable of multiplication and survival in these macrophages. F. tularensis non-capsular forms are characterized by higher superoxide-dismutase and neuraminidase activity than the initial strains, which may be the explanation of the phenomenon of their intracellular survival. At the same time the main biochemical signs of cap- strains (citrullinureidase, phosphatase and penicillinidase) remain unchanged, which determines the possibility of their classification with this subspecies.