[A rapid method for assessing the virulence of Francisella tularensis in vitro]

A rapid and simple method for the in vitro evaluation of the virulence of F. tularensis is proposed. The optimal parameters--the concentrations of bacteria and the substrate (phenolphthalein phosphate), the time incubation in the serum--have been developed and special conditions for strains of different subspecies have been selected. The proposed method makes it possible to greatly reduce the time of obtaining results and to exclude labor-consuming experiments on laboratory animals when working with large collections of F. tularensis laboratory and natural wild strains. Moreover, the method widens the possibilities of experimenters in the evaluation of the effect of some mutation on the virulence of the strain under study.